FLC Technology FLC 8S


New Head-Fier
Pros: 36 (or 80 if you consider not using the filter altogether) combinations to choose from.
Good Sound.
Good build.
Light - easy to forget they are there
Small - easy to fit into the ears
Cons: Doesn't cover extremes - high bass, high shimmer
Distortion on too much bass boost using eq
Price, considering that there are cons
I would've never imagined that my first ever post on this website would be a review of, the now old, FLC 8S, that I've had for years, and just when I'm thinking of buying a new set of different iems.

But I read that Forest Wei visits these forums, so I thought maybe I’d give my 20 cents (yes, not two), so that I have something to look forward to, the next time I plan to buy a new set.

So, let me talk about myself, the earphone and then about a design reconsideration that might help this design get even better.

"Water, water everywhere, not a drop to drink." - "The Rime of the Ancient Mariner" by Samuel Taylor Coleridge.

With 36 different (maybe not so distinct) combinations, it still leaves a standard consumer, "me", wanting more… bass, mids, treble… ok, maybe not mids

I did, before this (and still do), own a TF10. The only way I could even convince myself to buy them for the price, was that I had a few engagements that I had to honor, and I had changed cities and so, couldn't do the acoustics. Now, let me be honest... When I bought those, I didn't suddenly see the light at the end of the tunnel. I was expecting so much more… to be blown over, shocked, surprised… any emotion! But as I mixed my first track... god!!!... just perfect. That was when I realized the kind of gems they are. In time, I was hooked! Never touched an eq… ok maybe a little bass… ok, maybe just a little more…

I could never imagine going to any other; but as luck would have it... one day when changing the complys on them, the front part just popped out. $#@%!

I decided to try something new, and this time, I went through this forum, and bought FLC8S, because I could alter it to my taste.
Shocked, I realized, I couldn't... going through the 36 combinations, I found none that suit my preference.
(I'm not going to spend my time explaining the sound of all the filters (there are enough reviews for that), except tell you how did I get the most out of them)
And then, it happened... so far, I've always been someone who takes things out and puts back in... altering it, even when it's not meant to be altered. That explains blue led (instead of stock green) and custom mesh in front of the tweeters on my Yamaha MSP5A monitors, four three-way switches on my guitar, etc.

I like a fuller sound... very good bass (thumping with good impact) + good body (200-500Hz) that make the male voices sound deep and female voices powerful + corresponding intensity at 500-7K that so that there are enough dynamics, structure, and the sound doesn't feel muddy, and then a slow rise from 7K onwards so that there is a good amount of airiness in the sound... pronounced huskiness in the voice, crisper shimmering of high-hats, etc. Ok, may be a very shallow U.

The closest available combination for this was the red + black + gold filter.

But this still lacked some to the extent I liked... I needed more bass, more body, more shimmer.

So, the first to go, was the LF filter, then the MFHF filter, and then the red came in... or was there already.
Now, it was almost there...
Unfortunately, though this was the closest to what I liked, it brought in distortion… lots of it. The sound started to feel like I was pushing it beyond its limits.

Though the earphones weren't meant for this kind of configuration, I think a change in the design of the ULF (and maybe even the LF) filter could’ve helped in its use as such.

With removal of the LF and MFHF filters, we are letting the diaphragm vibrate freely, instead of giving it resistance to keep it in control, by keeping the two filters in.

This, coupled with the addition of the red filter that doesn't let any air pass through the ULF vent, I think, creates some kind of incorrect pressure chamber; free movement at one end and very strong restriction at the other.

OK, now, what allows the changes in the sub-bass response? The red, black and clear filters, right?
These work on the principle of stopping/resisting the airflow though the ULF chamber. This is not very efficient.

Now, please try this, use my config, pump up the bass a bit, and first try to recreate the issue I face.

Then take the red filters out and tape the hole instead. You'll see that the bass reduces just a little bit (still a lot higher than black filter) but clears up the muddiness a lot.

This happens because although you've closed the hole, you've added a little more breathing space for the diaphragm to move.

I know that the diaphragm was never thought of, to work under these conditions.

The question is, “why?”. Was is not expected that some people would like the bass a lot more. Even if you use red, black and gold filters, this happens if you pump up the entire bass region using an equalizer.

So, a better ULF filter design would've been, maybe a larger hole, and the filters in the form of a ring with a diaphragm made from a balloon-like material with varying tension depending on the bass response required. Higher tension for more bass and lower tension for less bass. This allows the diaphragm to have certain restriction in movement and aid the diaphragm in returning to its original position.


So, I’ve been using these without the LF and MFHF filters, and with a balloon cut-out taped at the hole of the ULF filter.


This brings the bass somewhere between the red and black filters but the distortion has reduced considerably. The distortion is lesser than with black filters and boosted bass. This also seems to reduce the harshness in the sound.

Removal of the LF filter completely has given a fantastic body to the sound, the vocals, lower keys on Pianos LFOs etc. Downside, the sound feels a little closer.


The removal of the MFLF filter has opened up the mids and highs in a way that has flattened the sound out. I miss the airiness of T2s though.


So, there you have it... a few more combinations, beyond the 36.
Should make the 8N more appealing, but you can't go wrong with this one either, especially if it's available for reduced prices.


Reviewer: The Headphone List
Pros: Great sound for almost any taste or mood. Adjustable tuning. Comfort. Size. Price.
Cons: Cable is a bit springy. Filters can be a challenge.
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~::I originally published this on THL. Now I wish to share it with my Head-Fi fellows::~

MusicTeck provided the FLC8s free of charge for the purpose of my honest review, for good or ill.

FLC8s on Amazon

MSRP: $355
Hybrid design
2x BA
1X Dynamic Low
Impedance: 11 Ohm
Sensitivity: 93 dB/mW
Frequency Response: 20Hz-20KHz


That stalwart chap Andrew over at MusicTeck emailed me one day and asked if I was interested in reviewing FLC Technology’s flagship IEM, the FLC8s. Understand, this is a famous earphone. It took the community by storm a year or two ago. I did quite a lot of reading on it back then, and even had the briefest listen to a set in a café when I met up with a friend and fellow reviewer in my area.

Naturally, I told Andrew “Yes!”

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I like almost everything about the FLC8s.

Beginning with size and shape. These are seriously comfortable IEMs. They are light-weight, and ergonomically righteous. You can insert deep, or shallow, if you have the right size tips. They do not fight you. Wherever your desires lie, the FLC8s will accommodate.

The cable is… okay. It’s light, which is good, but it’s also rather springy, and can get a little out of hand. I would like to see a tamer solution in their next release. This is really just about my only complaint about these earphones, and it’s a minor one, all things considered.

FLC Technology includes a high-endurance, anodized aluminum puck-shaped travel case. I’ve used a number of these over the years, and they work quite well. Very protective.

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This IEM can be tuned using swappable parts at three points. Each point has three possible filters. This makes for a tuning variety of 36 distinct signatures. Some of these filters can be tricky to work with, due to their ridiculous small size. Always work on a flat surface, and be ever so careful. Losing one is all too possible.

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Now… there’s no way I’m going to describe all 36 signatures. In fact, I have not listened to them all. After reading the manual, I installed Red, Black, Gold. Then, after speaking with a friend, switched to Red, Black, Gunmetal. I have not experimented further. That is the sound I like. It is the most bass-heavy and warmest, despite what the manual claims.

So as you read my sound description, remember, the other filters can give you significantly less bass and more treble, if that’s your thing.

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Again, my impression of how the FLC8s sounds is based on the Red, Black, Gunmetal filter setup. For me, the Gold nozzle filter was still a little too bright in the treble, and a friend suggested I try Gunmetal. This sounds just about perfect to my ears, with the biggest bass, warmest mids, and least harsh treble.

The FLC8s is a fundamentally clear, detailed IEM, and with the right filters, counterbalanced for delicious warmth. Tonal richness mingles with transparent, highly articulate rendering. The weight of the notes is on the lighter side, but do not feel hollow. Instead you get a thinner, airier quality. Yet that dynamic bass is ever-present to keep things grounded and deep.

FLC has struck a curious balance between clarity and detail, and a relaxed presentation. It has all the vibrancy of a quick performer, but feels laid-back like a much warmer transducer. Whatever trick they’ve pulled, I approve. These are a very easy listen.

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No matter what filter you use, the treble is on the brighter side, and sparkles freely. I find Gunmetal warms it up the most and is quite pleasant to my ears. Using Gold, it was a little fatiguing. Listening to Gunmetal, the highs are well-extended and smooth. There’s quite a lot of air, and light bathes the stage, revealing everything. Symbols and high-hats become prominent in the mix. Textures sharpen into relief. Details galore!

If you want laid-back treble, these are not the IEMs for you. Even with a dynamic driver dedicated to the low-end, the highs are really FLC’s main asset. You can feel the effects on every note, in the transparency and cleanness. The treble is not the finest I’ve ever heard. There is a slight glare, and it will bring out the sibilance if the recording contains any. Indeed, the FLC8s is a revealing monitor.

The mid-range is where that incredible balance shines the brightest. It’s so rich, yet so clear. Honest, beautiful warmth imbues the acoustic guitar, but never at the expense of precision. The intricacies and grain of a vocal piece are showcased in full, all while possessed of subtle lushness.

The romantic notions of the FLC8s are there, though tempered by high levels of technical proficiency. Voices sit large, center stage, with clean boundaries. The empty spaces around, and especially behind the vocals, are filled with a fairly black atmosphere, adding to one’s immersion in the music.

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I hear the mids as quite linear and coherent. From male vocals to female, the characteristics are the same: Warm, clear, and extremely detailed. They are powerful and very present, but not shouty or unnatural.

Oh that sweet, sexy dynamic bass. Some people find hybrids a terrible mismatch of tone and quality, but I love them. I have a passion for Balanced Armature IEMs, but a Dynamic Driver delivers a low-end like nothing else in this form factor. Indeed, if you’re using the bassiest filters, the FLC8s is awfully satisfying. It’s not outright bass-heavy, but the lows are emphasized enough to create a thumping, driving force to the music, with great warmth. It’s likely more than some purists want, but as always, there are filters for that.

Sub-bass is raised a bit over mid-bass, and there’s a gradual decline through upper-bass into mid-range. This produces a visceral, rumbling low-end, but one that doesn’t suffer aggressive bloom, and doesn’t bleed into the vocals. It’s tight and controlled, yet mighty as ****. The resolution and texturing of these sub-registers is impressive. FLC generates such a large, deep bass line. Its timbre is fulsome and luscious. In short, I’m a big fan.

Soundstage is not great, but not depressingly tiny, either. In truth, it’s sufficient to capture your imagination and hold you in the illusion. And at the price point, I’m not sure there is better. Imaging is excellent left-to-right, and okay on the depth axis. The stage itself isn’t very deep, so what do you expect? FLC8s resolves at a high level for a mid-tier IEM. It does a fantastic job rendering all the elements in sharp detail. And those elements have better than decent separation. I’m going to say it: these IEMs are stellar examples of what $300+ can get you.

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Oriveti’s New Primacy ($299, Review HERE) is another three driver hybrid, with the DD dedicated to bass. It is warmer and less clear than FLC. The bass is flabbier, with a notable mid-bass hump which does cloud the vocals quite a bit. NP’s treble rolls off earlier, making for a less airy stage and less note articulation. FLC8s is to my tastes a proper upgrade to an already excellent IEM in New Primacy. It separates better, renders at a high resolution, and produces a slightly larger soundstage. If you ask me, FLC’s normally higher price-tag is indeed worth it in this case. Between these two, I go with the 8s every time.

Now… the DUNU DK-3001 (currently $469, Review HERE) is an interesting comparison. Here we have a 4-driver hybrid, with a king-hell 13mm DD for bass. It’s a lot like the FLC8s, only smoother, gentler, and altogether more refined. It flows like a clear blue stream and is one of the most pleasant-sounded monitors I’ve ever heard. The bass is everything the 8s is, even tuned the same, only more organic and a goddamn force of nature. The vocals are just as clear and transparent as the 8s, only liquid, and with a less aggressive presentation of details. DUNU’s treble is much smoother and more linear in its rise. And it extends higher, giving even more air to the stage. In fact, the whole slope from bass to treble feels more coherent. Not that the 8s sounded chaotic, but when you switch over to the DK-3001, you hear the difference. Even soundstage is wider and deeper with DUNU. Separation and imaging is about the same, both being super good examples of quality. The only advantage the FLC8s may have over DUNU is in resolution. I feel the 8s is a touch sharper. Oh! There is one other thing FLC does better: Ergonomics. The DUNU DK-3001 has monstrous problems in this area, and FLC is a f**king champion. The difference is so significant it could mean a decisive win for the FLC8s.

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My reference player is the Opus#2, and this happens to be a wonderful choice for FLC8s. With its neutral-warm tuning and strong dynamics, it adds an uncolored, bold flavor to these IEMs. Opus renders weighty notes, and a robust, yet refined production. This helps to put some meat on the bones of those thinner FLC mids. Last but not least, Opus’ truly expansive soundstage pushes the 8s to its full potential.

Cayin’s very, very, VERY soon to be released N5II is also neutral-warm, but with a little extra treble energy. It’s a whole hell of a of lot like the Opus#2, but just a small step down in quality, and much less expensive. It pushes the clarity and smoothness of the 8s. The treble seems to take on more air. The bass grows in liquidity, but loses a touch of that visceral impact. Vocals render a crystalline image that is not as natural to my ears. Still, this pairing is awesome and oh so enjoyable.

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For the very best in budget range, the Shanling M3s is a delightful choice for the FLC8s. It has a killer low-end, vital, transparent mids, and superb treble presence. It renders at a higher resolution than any of the other budget DAPs I’ve tested, which helps to showcase the 8s’ special talents in that arena. Shanling’s relaxed presentation nudges the 8s a little further down that path, reducing the overall dynamics. It’s a player that performs beyond its price, and brings out the best in some of my more shockingly expensive IEMs. The FLC8s gets everything it needs, and then some.

Alright. There you have it. FLC Technology created a fiendishly good IEM with their FLC8s. Now I understand where all that hype came from. These perform well outside their expected range. The 8s is comfortable, light, easy to use (except some of those filters are a right pain to replace. Be careful!), and did I mention, sounds incredible? The fact is, at this price, I’ve never heard anything better. The FLC8s is an unequivocal recommendation.



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Ambient Lights

New Head-Fier
Pros: Clarity and naturalness far beyond its suggested price. Coherent and immensely spacious. Supremely precise imaging. A must try with Grey/Grey/None configuration and small Comply TX400. Exceptional comfort. 36 different tuning options to change the sound (and even more if you get creative!) Hear what you want to hear, listen what you haven't heard and even more with limitless expanse.
Cons: The stock silicone tips are really bad for tonality. The 7N braided copper cable is microphonic (even with the IEM being literally designed for over-ear use?) and produces audible cable noise with any movement unless higher volumes are used. Very minor flaws as both can be easily solved.


A current university student on a limited budget here. Subsequently, I don't have nearly as many frame of references as others have (but I do check out the nearby audio store and try out the common open headphones!) I'm not a super enthusiast (yet?) about audio, but music means a lot to me. My files are either lossless/uncompressed from Bandcamp or wherever I can get the source version from. I get some of the basics of high fidelity audio such as sound signatures, presence range, etc. but I'm definitely not a sound engineer. Music is subjective - hence, don't expect a superlative impartiality of sound explanations from me!

From reading countless comparisons and reviews across the wide internet, I ended up with the choice of three in-ear monitors that I believe matches my sound preference: neutral (negotiable, the upcoming aspects are not) with the greatest emphasis on clarity and spaciousness. The three IEMs I had rounded down to after an extensive multi-language search were the Etymotic ER4SR ($349, single balanced armature, known to be the benchmark of IEMs for a good reason), the Audeze iSine 10 ($399, planar magnetic IEM) and the much, much lesser known FLC 8S ($350, 1 dynamic driver + 2 balanced armatures hybrid). Though I haven't tried all three (the perks of living in Oceania... this is not one of them), both the ER4SR and iSine 10 had quirks that became problems for me: the former for deep insertion and fit (I bike as a primary means of transport and the ER4SR would stick out against my goggles; anything but foam tips are not comfortable enough for me to listen for long periods of time) and the latter for having no isolation, supporting Apple devices only while having an off-tone, massive peak between the 1-2 kHz range (the cipher cable they later developed to address this does not match my needs for an IEM). Being a university student studying full-time, I did not have the opportunity or money to splash around to try all these excellent and critically acclaimed in-ear monitors. This was a - very - luxury purchase I have made for myself, and I had absolutely no room for regretting a purchase. Ultimately, after reading many reviews of the FLC 8S, all the goods and bads (one saying that the iSine 10 was so much better (ehh no) than the FLC 8S - in hindsight, that person probably didn't tune their FLC 8S very well) I decided on purchasing the FLC 8S knowing that it would be the least regrettable purchase decision out of the three considering its advertised flexibility of 36 different tuning configurations. And so I brought these on sale for ~US $300 from Lend Me Ur Ears (great customer service, by the way) and eagerly awaited and withheld myself from excitement to try them at the right time and place of mind.

I brought the FLC 8S with my own money and felt the need (without anyone's suggestion) to share my experiences with these high fidelity in-ear monitors.

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Misleading first impressions

If you experience sibilance and/or hiss with the FLC 8S, throw away the stock silicone tips and use memory foam tips with a good seal in your ear.

So I prepared mentally and physically to listen for the first time. After hearing so many amazing reviews about this IEM, I was completely ready to be blown away. Putting on the smallest silicone tips (so I could get the deepest and clearest fit into my ear), I set down for the revelation of awesomeness.

I was blown away by how horrible the stock tips with Grey/Grey/Gold was and how sibilant they sounded.

Literally, I played a track with NO vocals and I heard hissing (which disappeared when I pause the track; not present in any other IEM I have, so I'm 100% sure it's not equipment) coming from the treble. Changed to another track. Still hissing. A vocal track. The vocals sounded like a ROBOT trying to mimic a snake rattle. They weren't even pronouncing 'S' sounds! Everything was hissing and sibilant so badly, I thought of returning the IEM for repair 10 minutes after I opened the box. They sounded worse than broken. But then I had a revelation of my own. I was going to change to foam tips anyway, but it struck me that the smallest stock silicone tips was the issue (I might miss the "best treble extension" stated by FLC... but with that sound. No. Not at all).

So I changed the tips to Comply TX400 (smallest size, the one with the waxguard filter). It was as if an entirely new experience of the FLC 8S opened up to me. And they did. They stopped sounding sibilant and broken. Literally, all the hissing disappeared from any of my tracks. No exaggeration, it was completely gone. And its not like any other variable could have caused it either, the hissing was so bad that I removed the stock tips after ~2 minutes of rapid-fire listening of many of my tracks. Suddenly, they sounded natural, incredible and normal (the incredible part is helped a lot by the TX400, great pairing to balance the sound of the FLC 8S) like what you would've expect from any non run-overed high-end IEM.

As such, I recommend that you take hold of all the stock silicone tips that came with the FLC 8S,
and throw them away.

(At least don't use them and look for alternatives, ESPECIALLY IF you are hearing unnatural tin robot sounds/sharp edges with them).

Second (unabridged) thoughts on the stock silicone tips

After seeing others praise the stock tips, I decided to give them another try. This time I used the medium size and made sure to get the best seal as I could (doesn't help that these do not adjust to the shape of your ear canal like the complys - felt like it could uncomfortably pop out of my ears at any moment). Tried with the track that I heard unlistenably terrible hissing and sibilance (Krys Talk - Fly Away <Mendum Remix>) and the awful hissing was mostly not there any more. Still, the treble stands out too much and reduces the amazing coherency and timbre of the FLC 8S. Sibilance ("WEU'LL SSHAYSSZEEEE") was still there. On other tracks, the brilliant no nozzle filters configuration started to sound shouty, unnatural and off-tone with the medium stock silicone tips. I did hear marginally more treble detail with the silicone tips, but I'm not sure if you'd really want to hear that with this IEM given that its midrange clarity is absolutely transcendental. I don't think the "most treble extension" silicone tips is a good combination if you want natural clarity from these IEMs. Also they diminish the FLC 8S's awesome detailed subbass and midbass (regardless of your filter configuration) by a lot. This is from someone who doesn't even like bass - it's as if the stock tips absorb the subbass impact or something. Compared to the complys, the stock tips made the sound somewhat tinny and far too bright - it lacks the fullness and wholeness that the comply gives with the IEM. Swapped back to the Comply TX400, and all became right with the world. The coherency, naturalness and clarity of the FLC 8S with the Comply TX400 is just incredible - a match made in audio heaven.

TD;LR stock tips changed from discard/10 to 3/10 listenable with proper fit and improving bass response through red thumbstack. Stock tips has poor bass response, making the IEM sound tinny. Small Comply TX400 (medium and large sizes causes recessed mids and muddies everything up) with good ear seal reveals the capability of the IEM's tremulous subbass while evening out the sound on top of making it feel like its not even on your ear - highly recommended. With it, I can not imagine a better pairing in terms of naturalness and effortless music. If you think that the FLC 8S is too bright or sibilant, then you owe it to yourself to try them with the small Comply TX400 - an incredibly even and harmonious tone awaits you with this pairing.

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The FLC 8S comes with an earguide hook that you can place on the cables. At first, I struggled for a good 10 minutes to even put the thing on until I realized that the ear hooks actually had "L" and "R" imprinted on them. Trying to put it on the first few times was rather discordant, but now that I know how to properly put them on it only takes me about ~5 seconds (make sure that the ear hooks cover the entire part of the cable; put the ear hook over your ear first, then guide the IEMs into your ear). The ear hooks were very soft and comfortable for me, most of the time I forget that it's (along with the super lightweight IEM) even hanging on my ear (if not for the incredible sound that these produce, that is).

The braided pure copper cable produces a lot of cable noise and should be replaced if you are intending to breathe and/or allow your heart to beat while listening to the FLC 8S. Well, its not actually that bad, but given that the IEM is designed to fit over-ear and yet still produces any microphonics at all (just from moving your head slightly, but the cable noise from this can be unnoticeable by increasing the volume), it definitely is a weakness to consider. I wear my IEMs with the cable over my back so that I never touch the cables and it stays more stable while moving (and also reduced microphonics to zero in my other cable-noisy IEM), but the FLC 8S cable still produced very little-but-still-there microphonics when I did this. For most people, the microphonics will be gone once you increase the volume, but if not, you should strongly consider setting aside the stock cable and seek an alternative, (non-cheap because the FLC 8S deserves great cables!) non-microphonic cable especially if you plan to move around a lot with this IEM. Newer FLC 8S comes with a revised pure copper cable (its more deep teal in color) with a proper non-cheap looking cinch and without the memory wire. I don't notice any stiffness and discomfort with this cable, I was able to sleep listening to the IEMs and the cable got out of the way without ricocheting and hitting me in the face like the other stiff cables I've tried, so I'd say the stock cable, sans microphonics, is actually quite nice.

They are also 1.2m long (for both the 7N pure copper stock cable and the 6N pure silver upgrade cable), which considering that includes the over-ear design may be too short for some. Understandably, these styles of cables are rather expensive (just look at how much Ultimate Ears sells their pure silver cable for... I'll let you guess. Over 60% the price of the FLC 8S... yikes) so I wouldn't consider it a flaw as you can use your own cables either way.

The socket is TF10 and is 0.74mm, so cables apart from FLC's own pure silver upgrade cable could potentially make the earpiece socket larger and slightly loose. They actually advise not changing cables often for the IEM's longevity, so these quirks should definitely be taken into an account if upgrading the cable is to be an attractive option for you.

I'm trying to blow holes at the FLC 8S's possible weaknesses at this point. Aside from the tiny thumbstack and cylinder filters making it potentially difficult to change on the go (I sort of got used to it and can change more often without the filters going and flying everywhere... I think. After getting used to the changing (grip the thumbstacks securely with your fingernails, push down from an angle opposite to the nozzle), it only takes me ~8 seconds assuming that I gripped the parts properly so that it doesn't fly off. Besides, considering how small these IEMs are it's really a given physical limitation) there really isn't much else you could criticise about the FLC 8S. Especially the sound. You can't make a tuneable IEM without being at least very good in all parts of the audio spectrum after all - and for that, they have done super well. I hadn't realised until now that 'You're Not Alone' by CMA actually had cymbals behind the empowering bass. It sits far behind it and is a bit subtle. With sibilance I probably would've just thought that the bass was distorted (its not, the artist's tracks are amazing and well-balanced) because I wouldn't have been able to distinguish between the overpowering bass and the subtle treble. I have no problems doing that with this IEM! The FLC 8S does a superb job of covering the general flaws of IEMs, and I think its very unlikely that its physical aspects would cause issues for anyone. I wouldn't even consider their custom shelled version because the universal one already fits so well for me. But that is an option if one finds the FLC 8S to not fit as well (not likely from what I can tell out of the countless impressions I've read, which is a very, very good thing for a universal IEM).

Impressions Update!

(The review of the FLC 8S continues down below!)

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75 Ohm Impedance Adapter

By now, I have been listening to the FLC 8S (with small Comply TX400, no nozzle filters) for quite a while, and as such I have been accustomed to its wonderful sound. I had thought that the FLC 8S's strengths was its clarity at lower volumes. I felt that it sounded more whole when you didn't increase its volume to loud. I was also looking for ways to remove crackling sound/electronic distortion and noise when using sensitive IEMs at very high volumes (its a general characteristic of IEMs), but was skeptical of impedance adapters as they are known to change the frequency response (compared to something like an iFi iEMatch for example). I was concerned that the frequency response changes would affect the coherent tuning of the FLC 8S - let alone not knowing what the added power through the impedance adapter would do. I first tested my theory on a single dynamic driver 16 ohm IEM I had around but could not explain the subtle difference I heard there very well. Moving into trying something that isn't very well understood, I wondered if the risk would be worth it.

That was what I thought, until now.

Using a good impedance adapter, the FLC 8S suddenly sounded much more whole to me. The entire sound spectrum is more - defined - everything is even clearer than it was before (an aspect that was already superb without the impedance adapter), and more importantly, it sounds slightly more lifelike - as the sound is more harmoniously balanced (but not flat) at higher volumes. The sound is no longer fatiguing, shouty and somewhat harsh at high volumes, and I don't notice any loss of detail compared to without the adapter. Actually, there is much, much more detail to everything now. In previous tracks that I thought only had one or two layers of vocals, I can now distinguish 3 or more if the track has it. Additionally, I notice more natural decay to the sound of everything, hence the sound being more true to life. Is this unlocking the potential of FLC 8S? The never-ending discovery of the IEM's capabilities continues. If this incredible surpassing improvement can be had with a 15$ impedance adapter, it's hard to imagine what awe-inspiring sound would I be able to hear by improving my equipment. The FLC 8S surprises me on a constant basis - it's a ridiculous thing to say, I know - and I am rewarded by an empowering sound that makes high-fidelity audio worth pursing all the way.

You think I'd be exaggerating when I said that. But really, I'm not (at least what I'm hearing makes me think that way). With no nozzle filter, small Comply TX400 and a 75 Ohm impedance adapter, the FLC 8S creates a sound that's so magnificently clear, it absolutely deserves to be heard. It's important to note however that while the impedance adapter makes the entire sound spectrum more defined, it most notably increases treble resolution and quantity (or at the very least the perception of it). What this means is that it may sound excessively treble-heavy and artificial with the stock silicone tips. This is one of the reasons why I've emphasised the necessity of the small Comply TX400 in balancing the sound of the FLC 8S. The waxguard filter reduces the sibilance and hiss (i.e. the artificial sound) and keeps the sound balanced and cohesive (in actually providing bass response... *cough* stock silicone tips). The impedance adapter also stops the music from trying to overwhelm each other as if every frequency is vying for your attention. For example, in the track Titanium by David Guetta, the primary vocals before the chorus are backed up with two layers of secondary vocals that sing in the opposite tone to the first. Without the impedance adapter it was very difficult to hear the secondary layers as the primary vocals are very forward and loud, drowning out most of the secondary layers of vocals. With the impedance adapter, the secondary layers come out alive and clear and compliments the base vocals pristinely, thus making the sound more complete and dynamic as well as multi-dimensional thanks to the improved ability to hear echoes and more subtle details. Without the impedance adapter, I don't listen to any of my IEMs at a volume beyond medium-high (the distortion and electrical noise/crackling at very high volumes with sensitive IEMs obviously doesn't help with this. I just use Neutron's compressor to eliminate electrical noise/sound distortion from the source entirely. No iFi IEMatch needed!) I think the impedance adapter might be making the sound signature slightly more neutral, but I can't say for sure. Basically, the empowered everything due to the impedance adapter may cause the sound to be off depending on the ear tips that you use. Try it out with the Comply TX400 and you can get the clear treble without the terrible sibilance! Win-win!

I can hear even more details, even more easily (sounds like a broken record by now, I know, but really!), cymbal sounds now sound improved in resolution and distinguished from one another, which helps a lot with realism and the presentation of sound. This isn't just in the case of putting the green nozzles on and focusing primarily on the treble - its much better than that. Everything is more powerful, multidimensional and embodied at high volumes compared to without the impedance adapter at roughly the same volume range, listening by ear. Without the impedance adapter, I hear 6 to 8 layers in some music. With the impedance adapter, I hear 10+ (including the really subtle breathing and voice echoes!) With my midbass boosted IEM, the impedance adapter made the speech echoes of Rameses B's Moonlight much less blurry and more noticeable (FLC 8S without impedance adapter is completely clear here by comparison). Without the impedance adapter, I noticed things sounded less complete - as if there were gaps in the sounds of the piano and instruments, or that they were shallow and less whole at higher volumes (or that they were cancelling each other out). Using the impedance adapter have made it much easier, less fatiguing and more enjoyable to listen to any of my IEMs at higher volumes. Does this potentially suggest the scalability of the FLC 8S? I'll definitely try new audio stuff and find out!

But don't take my word for it. Try out a good 75 ohm impedance adapter with the FLC 8S and hear the (awesome) differences yourself!

Neutron - Crossfeed | Surround Sound

By now I have tried many things on my quest to bring out the best possible sound from the >magnificent< FLC 8S. I have used the 75 Ohm Impedance Adapter for a while now, and while it does reduce listening fatigue at higher volumes, the added length makes it cumbersome to use when you're out and about. So I have been moving levers around in Neutron's Crossfeed and Surround Sound DSP settings and found that, with the right configuration, these can have the effect of reducing listening fatigue overall while also increasing soundstage depth (for Crossfeed) or soundstage width (for Surround Sound) significantly. The sound improvements are far greater than even the praises I put out for the impedance adapter, I don't think I could accurately describe the experience in words. It's an entirely new dimension of sound (maybe literally with Surround Sound) that I have never experienced in any headphone or IEM - ever, and the FLC 8S's superb technicalities and tuning ability have allowed me to hear and discover this new galaxy of sound better than any other sound producing equipment I have tried.

Descriptions of the perception of where the sound comes from may vary based on your setup, the ear tips that you use, ear tip insert depth, and your configuration. Oh, and your own ears, too.

These are the greatest and most significant improvements in sound I have heard thus far.


Music flows serenely in the background, allowing you to be focused and immersed in other tasks. Improves soundstage depth with the side-effect of lowering the volume and pushing the music back noticeably, making music very easy to listen to.

Idle listening to help with focus and flow.

Effect Parameters

Filter, Hz - 250
Level, dB - 0.01

Works with any filter combination and in combination with the impedance adapter.

Moves perceived origin of sound from the area around your mouth to the area in front of you. Depth of sound can be much more easily discerned. Sound no longer has the obvious piercing-like effect of coming from the left or right speakers exclusively in binaural tracks or any type of music.

For the best 'listening to music lightly in the background' experience possible, I use Clear - Clear - None + Comply TX400 as well as sometimes turning on the parametric equalizer with BW 1.00 -3 dB reductions between 20 to 250 Hz. This achieves the most unintrusive, freeform sound I've ever heard.

Surround Sound

Vocals span the space around your head, creating a large area of perception for audio. The sound is not perceived close to you or has the left speaker/right speaker obvious sound location pinpointing, which also makes it comfortable to listen to like crossfeed. Surround sound demands more of your attention naturally due to the expanded soundstage width.

This effect is incredible with some music, particularly vocal or choir, but would probably sound veiled and warped with other, less vocal focused music.

Listen to 'What Becomes Of Us' by Takeharu Ishimoto for an extraordinary demonstration of what surround sound can do to music.

Effect Parameters

Filter: Low-pass, Frequency (Hz) - 800
Filter: High-pass, Frequency (Hz) - 16000
Attenuation, dB - 5.00. Increase if music sounds warped.
Delay, Time - 20.00

Surround sound might not work well with certain genres of music and some filter combinations.
For example, with orchestral music without a vocal focus, it tends to move the perception of the sound from the left and right speakers to slightly behind your head, which does not work very well. Electronic music may sound off with surround sound on, but with the configuration that I use (Clear - Clear - None + Comply TX400, silver upgrade cable) I get used to the sound quickly and keep it on for its massive benefits in tracks containing vocals - unless I want to listen to music in the background, where I would switch to crossfeed.

With the 75 Ohm Impedance Adapter, Red - Clear - None + Comply TX400, it makes music sounds astronomically powerful, balanced, astonishingly spacious, detailed and clear in all types of music.

75 Ohm Impedance Adapter, Clear - Clear - None + Comply TX400 and silver upgrade cable (plus the reduced bass equalizer I have mentioned in the crossfeed segment, but that's just my personal aversion of bass) makes for an enjoyable analytical or close listening of music.

Moves perceived origin of sound from the area around your mouth to the area surrounding you or to the space of your mind. Position of sound is much more precise. Details of music reveal themselves distinctively to you. Music is no longer being perceived as being produced by the speakers - it instead originates from the space around your head in a way that's impossible to describe. Neutron's surround sound is the most beautiful rendition of music I have ever heard.

Surround sound can cause music with high peaks in the midrange to crackle/be affected by electrical noise, or cause ringing in your ear due to hearing sensitivity or aliasing from using many DSP effects on a 44.1/48 kHz audio file. Neutron's compressor with the following settings can be used to eliminate crackling/clipping/ringing and other sound distortions like it (regardless of whether you use surround sound or not):

Ratio, N:1 | 2.00
Threshold, dB | -65.00
Knee, % | 100.00
Attack, Time (msec) | 0.00 (I had to set it this way so that Neutron doesn't cause loud audio popping when you pause/begin to play a track)
Release, Time (msec) | 60.00. This setting depends on the music, though anywhere between 10 to 200 should not affect music negatively from what I've listened and tested.
Output Gain, dB | 0.00. Might want to decrease if you still hear crackling/electrical noise alongside the music.
Look-ahead, Time (msec) | 0.00 (Set to 0 for the same reasons as attack, audio popping during pause/begin play from what I've tested)
Window (RMS), Time (msec) | 1.00
Limiter | Off

A compressor makes loud parts quieter, which can make it appear to flatten the audio (bass would be reduced to the same audio sound level as the midrange, whereas it's usually ~20 dB louder). It also reduces the volume massively with the settings I use to eliminate all sound distortion when using surround sound/higher volumes, so a good amplifier or a powerful audio source will be needed to use it at audible and enjoyable volumes. I don't really use the impedance adapter alongside the compressor with my setup, as even at the maximum volume (which would pretty much blow out eardrums if used without the compressor) it does not get loud at all. The compressor processes the audio and reduces the volume before it's actually sent to your DAC.

With how the compressor changes the audio spectrum, the maximum bass configuration

Red | None | None

could potentially sound more balanced, as bass is reduced by a lot with the compressor on.

If you don't particularly like bass, using the configuration of Clear | Clear | None and this surround sound setting may sound better in tandem with the compressor:

Filter: Low-pass, Frequency (Hz) - 800
Filter: High-pass, Frequency (Hz) - 5500. To focus on the midrange, as it is also particularly reduced by the compressor. But it really depends on your own ears and preference (higher values = more airy, less depth). Can cause sibilance if you extend the high-pass above this value, in which case you'll need to counterract it with equalizer to reduce frequencies 4k - 20 kHz depending on your preferences (if you still want the wide soundstage without the possible sibilance caused by attenuation extending to 16 kHz)
Attenuation, dB - 3.30. No need to worry about distortion/clipping with the compressor enabled, so feel free to lower the value as far as you'd like. Lower values (greater effect) are amazing for vocal focused tracks, but bad for music that already sounds very wide such as orchestral (though it can sound good using Red | None | None, as the bass balances out the midrange focus of surround sound).
Delay, Time - 20.00

If you hear ringing from piano sounds, using Oversampling (under Audio Hardware) and setting it to at least 8x (Neutron will oversample to the highest sample rate your DAC will accept) should significantly reduce it or eliminate it entirely. This is because using DSP effects can cause sound artifacts without enough frequency headroom to filter out distortions. I heard piano and midrange ringing at high (not just super high) volumes on the Shure KSE1500, a full-range electrostat which has its own dedicated amp and internal DAC that resamples everything to 24 bit/96 kHz. Similar story with other high-end headphones and IEMs I've tried, ringing most noticeably from the low mid sounds (250 to 800 Hz mostly, sometimes even up to 2 or 4 kHz), so I know that this is a problem on the digital side and not with the hardware. I'm guessing this would be caused by sound aliasing, and with oversampling combined with dither plus noise shaping, it will mostly be moved far above 20 kHz (made possible by the extra headroom from oversampling) and as a result becoming not noticeable, or at least not nearly as distracting.

With the compressor and surround sound on, voices may sound somewhat dry and artificial due to the changes in the sound balance. Setting surround sound to the parameters above should significantly reduce that, and increasing the bass through using red thumbstack and/or no cylinder filter should make it completely nonexistent. If you want to test out attenuation to find a value you like, the orchestral track 'Reverie' by James Everingham (it's available in WAV/AIFF format over at Bandcamp) might be good to use as a bass/midrange cohesion test, as it is already mastered to be very wide and as a result does not sound particularly good with surround sound on. Regardless, I'd say that surround sound is important to have on when using the compressor, as the volume of the midrange is reduced considerably and may sound recessed/dull/not very loud with surround sound off. The compressor setting I use to eliminate all sound distortion reduces the volume by something like 70 dB (probably more based on what the spectrogram is showing me), so increasing the volume to an enjoyable volume might not be an option depending on the power of your source (you could increase the compressor's output gain, but that might bring in electrical noise/crackling/clipping depending on your setup). Personally, I always keep the compressor on now, as I don't hear any electrical noise or ringing anymore thanks to it (piano music with high peaks like DJ Okawari's Luv Letter was practically unlistenable with surround sound on and the compressor off, as it clipped/crackled and caused ringing at every single note). After all, I'm listening to music - not testing the technical specifications of the THD/DNR/SNR or anything!

-- Note: take care when using the compressor and adjusting its settings. As you'll need to increase the volume level while using the compressor, the volume differences with the compressor on or off will be enormous. You really don't want to disable the compressor while you are playing music at a higher volume than you are used to (the volume that you usually use without the compressor turned on), as that will revert volume levels back to normal, which is of course not a good thing if you have set the volume way higher than usual in order to use the compressor. It's also a good idea to be vigilant when adjusting the Threshold, Window (RMS) and Output Gain, as those changes the volume output. If you are using something like a smartphone, be warned that any sound going to your headphone not coming from Neutron will not be altered by the compressor, and will play at the volume you have set. This can make using the compressor not viable if you are expecting to be interrupted from listening to music often by other apps, or you are using Neutron to play music in the background while you use other apps that also transmit sound to your headphones; basically anything not from the music player itself, unless you are willing to silence/specifically reduce the volume of all other sounds in their respective settings as well as your ringtone (ones that play through the speakers are fine). High volume will still be high volume (outside of the music you are playing through Neutron's compressor), so do keep that in mind if something like this could be a possible situation for you.

The differences that crossfeed and surround sound makes are just too significant to put into words. If you are interested in improving soundstage depth (crossfeed, surround sound to a lesser extent) or soundstage width (surround sound), try them out. It just has to be heard to comprehend the massive differences that they make to the sound.

FLC 8S - Pure Silver Cable .jpg

The Pure Silver (Single Crystal) Upgrade Cable

Let me preface by saying that the stock 7N pure copper cable (minus the microphonics) is already very good. Either the stock or the pure silver upgrade cable will offer great sound without issues (0.74 mm pins). The 99.9999% (this is expensive stuff) pure silver upgrade cable comes with memory wire which I can adjust to stop the cables from touching the back of my neck (compared to the ear hooks, which points the cable inwards slightly due to its shape). It also allows a more secure fit on your ear in case you're doing gymnastics or something with these IEMs. The cable is the same length, still with microphonics (though somewhat reduced maybe? but with more shape retention), so don't expect much of a difference in those areas. The upgrade cable does have 400D Kevlar at the core though, so it'd probably stop a bullet before failing out (the price would be mainly due to the single crystal silver they used - its not cheap). Any improvements in sound quality made beyond upgrading the actual IEM itself is not as large (unless your source files are really bad), hence divisive and subjective (we sure know that on this forum!), and depending on your setup and circumstances, the differences might be massive, it might be slight, or there might not be any perceivable difference at all. With that said, I'll try to describe the differences (and improvements) I hear when swapping from the stock pure copper cable to the pure silver upgrade cable deliberately and exactly. First, lets get some things out of the way first.

The difference between copper and silver is that silver transmit electrical signals ~5% better than copper. You can look it up and see why people even bother with expensive silver in high end equipment!

But would you really notice that 5% (real-world estimated, not likely to transfer exactly to listening experience) difference? Theoretically, it might improve sound performance (again, theoretically). But how would you be able to measure that? A cable shouldn't be changing the sound frequency (unless its very bad or is intentionally designed to do so) and an artificial model can only do so much to imitate the millions of different variables creating different overall experiences to the sound that makes audio fidelity perception inherently subjective. I can't speak for everyone, but since the audio-focused FLC released these cables (at a small sum of $100 dollars), I felt that these might actually make some differences (though I am not inclined to think so), or that they should if they bothered to make it given they said that they worked so hard on perfecting the 7N copper stock cable. So, now I got the pure silver upgrade cable (the FLC 8S really impressed me!), this is what I have noticed after listening with the stock pure copper cable then swapping immediately to the pure silver upgrade cable with my setup:

LG V20, Sabre ES9218 32-bit DAC (B&O Play tuned, frequency response and other technical measurements by zerodecibel)

- Rooted - modified build.prop to play 16/24 bit files natively past Android resampling

- Modified mixer_paths_tasha.xml so that 'Normal audio device' mode functions the same as 'High impedance device' mode

Neutron Music Player

64-Bit Processing - On

Resampling - Audiophile

Dither - On > under Dither: Noise Shaping - On | I use Neutron's DSP effects; Neutron's developers have said that it can be beneficial in that circumstance, otherwise this option makes no discernible difference

Subsonic Filter - Off

Ultrasonic Filter - Off

Hardware Gain - On

Generic Driver - On

Settings under Generic Driver

- High-Res Codec (Direct PCM) - On

- Hi-Res Speaker - On

- Hi-Res Bluetooth - On

- Custom Format - On

Settings Under Custom Format
According to Neutron's developers:

- Format - None selected (selecting anything under this will cause frequency resampling, see the ADB datalog below)
- Frequency - None selected (not necessary with Follow Source Frequency turned on - no option should be selected under here like under format)
- Mode - DIRECT (set everything else under the mode setting to OFF)

Follow Source Frequency - On

Frequency - None selected (this causes resampling, leave it unselected and your audio files will play directly with the actual frequencies that they have. There's no option to select anything here with Follow Source Frequency turned on either way.)

If you are curious of what the other settings not listed here in Audio Hardware does, check out the ADB datalog below.

With these settings, Neutron will show your files' native sampling frequency as it is sent out to your DAC under Audio Hardware instead of showing 48000 for everything (which is indicative of Android mixer resampling the file before the audio data is sent to your DAC). Depending on the music you listen to (especially those using high frequencies), the Android resampling causes a very perceptible reduction in sound quality, assuming that you have good headphones that will present to you the ruined sample frequency that is. I recommend bypassing the resampling if you're using anything running with Android if you can. But if you are running Neutron with the AudioTrack driver enabled by the settings above (which doesn't resample everything to 48000 Hz and plays at your file's actual frequency or the maximum your device can handle) then you don't need root and this shouldn't be a problem. Neutron also supports a bunch of DAPs/DACs with each new update where they automatically configure the correct settings for you, if that's the case for your device just uninstall/reinstall (your settings will be the exact same if the NeutronMP folder isn't deleted) and the option to enable Hi-Res playback on your device should come up. Aside from that, these settings should work too!

FLC 8S configuration

Red | Clear | None + small Comply TX400

Neutron not configured:

16 bit/44.1 kHz audio file

Output thread 0xe9183380 type 0 (MIXER):
Thread name: AudioOut_15
I/O handle: 21
TID: 1390
Standby: no
Sample rate: 48000 Hz <------------- this is android messing things up
HAL frame count: 1920
HAL format: 0x1 (pcm16)
HAL buffer size: 7680 bytes
Channel count: 2
Channel mask: 0x00000003 (front-left, front-right)
Processing format: 0x1 (pcm16)
Processing frame size: 4 bytes
Pending config events: none
Output device: 0x8 (WIRED_HEADPHONE)
Input device: 0 (NONE)
Audio source: 0 (default)
Normal frame count: 1920
Last write occurred (msecs): 24
Total writes: 19256
Delayed writes: 0
Blocked in write: yes
Suspend count: 0
Sink buffer : 0xea14d000
Mixer buffer: 0xe989a000
Effect buffer: 0xea14f000
Fast track availMask=0xfe
Standby delay ns=3000000000
AudioStreamOut: 0xeaaa5a08 flags 0x8 (DEEP_BUFFER)
Thread throttle time (msecs): 280
AudioMixer tracks: 0x00000001
Master mono: off
FastMixer not initialized
Stream volumes in dB: 0:-10, 1:-36, 2:-53, 3:-37, 4:-36, 5:-36, 6:0, 7:-36, 8:-29, 9:-96, 10:0, 11:-33, 12:0, 13:0
Normal mixer raw underrun counters: partial=0 empty=0
1 Tracks of which 1 are active

Neutron correctly configured with the mentioned settings above:

24 bit/44.1 kHz audio file

Output thread 0xe9670000 type 1 (DIRECT):
Thread name: AudioOut_18D
I/O handle: 397
TID: 6141
Standby: no
Sample rate: 44100 Hz <-------------------- android sampling eliminated
HAL frame count: 1792
HAL format: 0x6 (pcm24)
HAL buffer size: 10752 bytes
Channel count: 2
Channel mask: 0x00000003 (front-left, front-right)
Processing format: 0x6 (pcm24)
Processing frame size: 6 bytes
Pending config events: none
Output device: 0x8 (WIRED_HEADPHONE)
Input device: 0 (NONE)
Audio source: 0 (default)
Normal frame count: 1792
Last write occurred (msecs): 18
Total writes: 1091
Delayed writes: 0
Blocked in write: yes
Suspend count: 0
Sink buffer : 0xe9668000
Mixer buffer: 0xe8d37000
Effect buffer: 0xe8d25c00
Fast track availMask=0xfe
Standby delay ns=1000000000
AudioStreamOut: 0xeaaa6e98 flags 0x2001 (DIRECT|0x2000)
Stream volumes in dB: 0:-10, 1:-36, 2:-53, 3:-37, 4:-36, 5:-36, 6:0, 7:-36, 8:-29, 9:-96, 10:0, 11:-33, 12:0, 13:0
Normal mixer raw underrun counters: partial=0 empty=0
1 Tracks of which 1 are active

24 bit/96 kHz audio file

Output thread 0xe9b6c000 type 1 (DIRECT):
Thread name: AudioOut_1AD
I/O handle: 429
TID: 8603
Standby: no
Sample rate: 96000 Hz <------------- no android resampling here
HAL frame count: 3840
HAL format: 0x6 (pcm24)
HAL buffer size: 23040 bytes
Channel count: 2
Channel mask: 0x00000003 (front-left, front-right)
Processing format: 0x6 (pcm24)
Processing frame size: 6 bytes
Pending config events: none
Output device: 0x8 (WIRED_HEADPHONE)
Input device: 0 (NONE)
Audio source: 0 (default)
Normal frame count: 3840
Last write occurred (msecs): 25
Total writes: 1214
Delayed writes: 0
Blocked in write: yes
Suspend count: 0
Sink buffer : 0xe8a8c000
Mixer buffer: 0xe8aab000
Effect buffer: 0xe9b60000
Fast track availMask=0xfe
Standby delay ns=1000000000
AudioStreamOut: 0xeaaa5a78 flags 0x2001 (DIRECT|0x2000)
Stream volumes in dB: 0:-10, 1:-36, 2:-53, 3:-37, 4:-36, 5:-36, 6:0, 7:-36, 8:-29, 9:-96, 10:0, 11:-33, 12:0, 13:0
Normal mixer raw underrun counters: partial=0 empty=0
1 Tracks of which 1 are active

Settings confirmed by Neutron's developers to prevent high fidelity output:

- DSP Effect (Device)

- 32-bit Output (IEE 754) | resamples the audio, confirmed in ADB logs

16 bit/44.1 kHz audio file

Output thread 0xe9183380 type 0 (MIXER):
Thread name: AudioOut_15
I/O handle: 21
TID: 1390
Standby: no
Sample rate: 48000 Hz
HAL frame count: 1920
HAL format: 0x1 (pcm16)

This is what the same audio file played looks like without 32-bit Output (IEE 754) being enabled

Output thread 0xe966e000 type 1 (DIRECT):
Thread name: AudioOut_23D
I/O handle: 573
TID: 12619
Standby: no
Sample rate: 44100 Hz
HAL frame count: 1792
HAL format: 0x6 (pcm24)

- Low latency | bypasses high fidelity output, does not work. It's for supporting older devices without Hi-Res capability.

- Selecting any of the format options under format in Generic Driver | resamples the audio, confirmed in ADB:

Output thread 0xe5803fc0 type 0 (MIXER):
Thread name: AudioOut_D
I/O handle: 13
TID: 1271
Standby: no
Sample rate: 48000 Hz
HAL frame count: 192
HAL format: 0x1 (pcm16)

No custom bit format selected under format:

Output thread 0xe5b32000 type 1 (DIRECT):
Thread name: AudioOut_8D
I/O handle: 141
TID: 10993
Standby: no
Sample rate: 44100 Hz
HAL frame count: 1792
HAL format: 0x6 (pcm24)

Neutron pads 16 bit files to 24 bit to avoid the resampling issue, which is much better than any resampling happening.

- In Phillip G. Anderson's 'Winter', the subbass of the orchestral drums are tighter and more refined. The bass not only has more impact like you would expect from boosting subbass and midbass - the impact is clearer, as in the specific repercussions could be felt (I also felt this with the stock cable but the pure silver upgrade cable does this rumble effect more cleanly and distinctively). The echoes of the drums seem to extend slightly longer, making everything sound more natural.

- In the soundtrack 'What Becomes Of Us' from Final Fantasy Type-0, the female and male choirs sounded somewhat fuller (not in terms of soundstage depth or anything, but rather the opposite of 'thin' sound), I could hear the background layers of vocals a bit better.

- Hammock's 'Ten Thousand Years Won't Save Your Life' sounds fuller and overall more whole. The violins are more intimate and impactful.

- The piano in DJ Okawari's 'Flower Dance' and 'Luv Letter' sounds like they have more presence (not thin or forwarded - the instruments sound more balanced and is comfortably in their respective places), sounding more natural and slightly more real compared to the stock cable.

- The wall of treble in Porter Robinson's 'Sea Of Voices' sounds somewhat more powerful with a higher sense of density.

The improvements isn't just better resolved bass, though that would be the first thing most would notice when not listening analytically. In all of my tracks (even in ones that doesn't boost the bass very much), the bass rumble sounds and feels more detailed - there is more of it when the music presents bass (though still completely silent when it doesn't). Secondary layers of vocals sound more pronounced compared to the stock cable, though I do not notice an increase in treble quantity (which is a good thing as the FLC 8S already has a lot of treble). This makes the FLC 8S feel more powerful, not in a typical bass boosted sort of way, but in terms of offering a more realistic presentation of music. I can definitely see and hear why they call it an 'upgrade cable' for the FLC 8S.

A year after - Impressions update
My initial impressions were too modest. The silver upgrade cable is AMAZING with the sound it enables for the FLC 8S! The newer cables don't seem to have any audible microphonics at all, the cinch is now the same as the stock copper cable (i.e. no longer a cheap looking plastic tube, instead something sturdy and easy to use). No more memory wire that's shown in the impedance adapter picture above, but I've never found the lack of to be an issue (even while cycling) if I wear the cables over my back with the cinch up to the back of my head. And the sound. Everything is somehow even more clear, including the subbass (20 - 40 Hz) and lowbass (40 - 80 Hz) precision and naturalness that I've mentioned previously. I can hear the vocalists' breaths at the beginning of every sentence more easily compared to the stock copper cable, yet it still does not sound fatiguing. The entire frequency spectrum is just rendered better. That ~5% difference in conductivity between copper and silver is absolutely being utilized here (not to mention the expensive 6N 99.9999% silver purity), and if you're familiar with how the FLC 8S braided single crystal copper and silver cable sounds, I would go as far as to say that the differences will present itself to you.

For example, I have several music files that primarily uses the 19 kHz region at certain parts of the track (which the spectrogram shows it being as loud as the bass region; it manifests as faint light note scribbling/wind sound), on the stock copper cable it was audible and kind of there, but with the pure silver cable it was - easily - noticeable and effortlessly presented. Upper frequencies 16k to 20 kHz reminds me somewhat of the Shure KSE1500 (that I've demoed twice, pretty much unparalleled detail in mids and treble but Balanced Armature-ish bass with little to no decay compared to the stunning natural subbass of the FLC 8S's dynamic driver) with the silver upgrade cable, it's just super glorious. Treble sounds more accurate, but not harsh, and the subbass - I can feel the gentle but powerful and clean rumble of the subbass and lowbass in my chest and even down to my stomach if I turn the volume up high in certain tracks (like Nero's 'Promises') with the red thumbstack! Listen to the beginning of Max Richter's 'November' and you can FEEL the precise and clean rumbles with the red thumbstack filter (but it doesn't affect the clarity of the mids at all! Hybrid IEMs huzzah!) I've just mentioned how incredible the FLC 8S's subbass is with the silver upgrade cable, red thumbstack and easy-to-get-a-complete-seal small comply TX400, right? Listening to the combination as I'm writing this, I felt the need to say it again. I've heard top-of-the-line headphones like the Stax SR-009S and the Sennheiser HD820 and they do not compete with the FLC 8S IEM in subbass quality and naturalness at all. If you're looking for an upgrade to the FLC 8S, buy the silver upgrade cable (or if you're uber rich, import the ~2k USD clockwork gear tuning 135 sound combinations FLC Celeste from Hong Kong). I'll resolutely assert that there is no better universal and tunable high fidelity sound than this at the now ~300 USD price range after trying the stock copper for a while then switching back to the silver upgrade cable!

But, of course, this is my subjective perceptions of the improvements I've noticed. While I can definitely pinpoint the more defined subbass and lowbass (Phillip G. Anderson's 'Winter' is a very good example of this, as well as Torsti Spoof's 'Faith'), someone else with different audio equipment, music tastes and several thousand other things may notice something else entirely or nothing different at all. It's all subjective approximation either way. Some people might not be able to distinguish a pair of Beats over the Sennheiser HE 1 in a blind test, and that's okay too. What experience that person perceives and prefers is what matters. For me, the pure silver upgrade cable offers a nice improvement to the sound of the FLC 8S, and with that I'd say it's worth using over more convenient custom cables. After all, I brought the FLC 8S for its incredible sound; if you listen to music through IEMs a lot like me and you enjoy the FLC 8S's tuning capabilities and sound, it might be worth getting if price is not a factor - the pure silver upgrade cable presents a sound that is slightly more real and more complete in all types of music.

Subjectivity to consider

Sound quality is influenced by an astronomical number of factors - the genre of music you like the most (which generally determines the sound signature/IEM you would prefer), the shape of your ear canal, the sources of your music (smartphone versus dedicated amplifier, file quality), the list goes on. All these things could have the potential to affect sound quality drastically (again, dependent on your circumstances) as I've demonstrated with the smallest stock silicone tips and small Comply TX400 in my first impressions of the IEM, so your experiences can and probably will vary to mine. I am from a perspective that clarity and spaciousness above all else matters for high-end headphones, and with that said I am rather aversive to bass and its tendency to make tracks feel like a nightclub party (have used a bass reducer equalizer ever since I've started to listen music more attentively, which I now longer do with the FLC 8S because it is no longer needed - the clarity and balance is incredible). Of course, treble standing out is not a good thing (usually destroys the timbre and harmony of the music) so its a very delicate balance for me in the sound that I prefer. The FLC 8S allows me to achieve this balance and change the sound based on what I feel like listening to (upbeat EDM for biking, Ambient for relaxing/studying) which to me makes it understatedly unique compared to every other IEM on the market. Of course there will be more technically proficient IEMs out there (the electrostatic Shure KSE1500 for example), but the FLC 8S's versatility and comfort to my ear makes it the best use-everyday high fidelity IEM I could imagine. Because everyone will invariably have different experiences and perceptions to audio, I would like to speak from my standpoint, particularly the configuration which have led me to praise the FLC 8S so much. You should get a chance to hear these configurations first before modifying your expectations (for better or worse) of this IEM.

Small size Comply TX400 memory foam with waxguard
Comfortable and removed all sense of sibilance I heard from my first impression of the FLC 8S. For those who believe that the FLC 8S is on the bright side for an IEM, these will very likely change that perception in offering a more balanced and customizable sound.

What have blown me away:

Grey | Grey | No Filter

Immensely coherent and harmonious sound with stunning resolution, forwardness and clarity of the midrange.

Red | Clear | No Filter

Detailed energetic bass response with great clarity. Midbass recessed, but potentially offers a wider space of sound.


FLC 8S - Filters Capsule.jpg

The Sound|s| of the FLC 8S

Filters - Thumbstack [Subbass] | Cylinder [Midbass] | Nozzle [Midrange and Treble]

Colors, most to least respectively:



Green - Most treble
Black - Medium mids, second most treble
Gold - Most mids
Blue - Deletes treble and reduces midrange

(I will be calling the black thumbstack filter grey for coherency and color-coordination).

There is actually a lot more to know and discover about the FLC 8S beyond the claimed 36 configurations design. Changing one filter affects the rest of the frequency response and thus the sound. For example, using a clear clear black configuration will push the frequency peak of the black nozzle filters slightly from ~1.3 kHz to somewhere closer to 2 kHz (check out the graph measurements at innerfidelity for a comparison) compared to any other bass filters combination. This means that changing just one filter can have a larger than expected effect on the entire audio spectrum, particularly the midbass cylinder filters which determines how much airflow goes into the IEM. Basically, the FLC 8S can be VERY complex and advanced if you choose to go the advanced tinkering route (someone in this forum added an acoustic dampening cloth to their cylinder filter - the frequency response changes were rather interesting!). On a particular track that I found had too much treble coming from one side, I literally removed the cylinder filter with my hands from that side, WHILE listening to the IEM, and found that side suddenly becoming more coherent! It should be noted that the general issue of disjointed sound found in other hybrid IEMs is nonexistent with the FLC 8S. The combinations of drivers are exceedingly technically well-tuned that they overlap and blend in sound, creating a natural sounding hybrid IEM that doesn't sound off-balanced, being just as whole and pleasing as single-driver type style IEMs (maybe even moreso with the brilliantly clear, wide midrange of no nozzle filters i.e. what the IEM is wholly capable of in terms of 'soundfullness'). Now, I'm not advocating for mismatching the volume and frequency response of the IEM, but it shows the deep potential and customizability of the FLC 8S. I don't think I would be exaggerating in saying that these are perhaps the most customizable IEMs ever released (at least for the time being... new technology are so limited and expensive!)

Since I don't have frequency response graphs to show (the other reviews have already done an excellent job on this), I'll just (not word for word) quote FLC's founder Forrest Wei on precisely what the filters do.

"Without the ULF plug [Thumbstack], the earphone will be like an earbud; you could wear it to run.
Without the LF plug [Cylinder], the midbass is about 2 dB higher.
Without the nozzle, the mids will be higher around 2K Hz - vocal is more forward, the treble will lessen at around 4~5K Hz, sibilance will be less, but the treble would not be so solid and bright."

You could probably get it from his explanation on what the functions of the filters are. The purpose of the filters is to control how much specific sound frequencies are dissipated from the IEM before reaching the nozzle and into your ear. What this means is that there are actually even more (!!!) ways to tune the sound than the stated 36 configurations if you get creative with the no filter combinations.

No Thumbstack filter
This covers the area where the dynamic driver rests. It removes (maybe all) low-end subbass from the IEM and make it sound as if they sit outside your ear, even with a perfect seal. From what I've noticed, this makes energetic EDM tracks or anything reliant on bass sound bad as if the entire low-end frequencies are missing. This may be a good thing on some poorly mastered tracks or orchestral music, but for cohesiveness of sound, using at least the clear thumbstack filter for reduced bass (instead of removing bass entirely) would be recommended for most styles of music.

No Cylinder filter
This covers the area where the dynamic driver and two balanced armature drivers are situated. According to Forrest Wei, this option is the most bassy option of all, offering 2 dB more bass than the max bass filter (black cylinder). This is accurate in my experience, as the moment I remove this filter while listening I was greeted with bass energy that wasn't there before. Using no filters here provides more airflow for the dynamic driver, and in increasing midbass controls the presence of the higher end frequencies. Having no filter here at all noticeably reduced the clarity of orchestral tracks, particularly the piano where it became harder to discern the particular notes as you increase the midbass. To reiterate: removing the cylinder filter and using none will actually increase bass presence and energy. The clear filter here gives the dynamic driver the least amount of air (aside from taping over the port completely) for the bass, so you can tune subbass and midbass separately which makes the various interactions with the filters rather interesting - you could come up with some unexpected results by changing this filter in combination with the others!

No Nozzle filter
This is the final filter before the sound reaches your ear, and arguably its removal makes the FLC 8S shine. Using no nozzle filters as FLC founder Forrest Wei says will make vocals sound forward while simultaneously reducing the treble around 5 kHz (which according to the presence range definition you can find in the forums, would make instruments 'more distant and transparent'. I interpreted this as greater clarity and spaciousness on the FLC 8S). With no nozzle filters, the IEM becomes somewhat mid-centric, which would sound unusual if not for the FLC 8S's excellent technical capability. With no nozzle filters in place I was able to pick out minute details that was not present or less noticeable with the black, blue or even gold filters (the green filter was only partially equal with music that extensively utilise/mainly focused on the high ranges above 6 kHz). The sound could actually be characterised as an enhanced gold filter experience. Detail resolution expanded when I took off the gold filters and put the Comply TX400 on in its place. While the default configuration of Grey/Grey/Gold filters was great and supremely harmonious, using no nozzle filters made me felt moved - by the sound, and I found myself involuntarily moving to the rhythm with a smile on my face. No nozzle filters definitely deserves to be heard (can't say the same for no thumbstack filters). It makes the midrange sibilance-free and clear with impressive imaging and a great sense of expansiveness.

I can't say much about the thumbstack and cylinder bass filters as the preferable tuning of these are highly dependent on the music you listen to. Increasing any parts of the bass should eliminate any sibilance (with Comply foam tips plus waxguard) that you might hear on even the most awkwardly mastered tracks. I will say that the subbass of the FLC 8S (with red thumbstack filters) goes very deep. Compared to a V-shaped IEM with more midbass, in the track 'Winter' by Phillip Anderson, the drum parts were seismic (if you have a complete seal with foam tips) and I could feel the specific repercussions of the drum's echoes. With the more midbass V-shaped IEM using the same foam tips, I was not able to feel the same effect, it didn't really came close to reproducing the detailed and powerful subbass of the FLC 8S. With red thumbstack, its pretty strong in the subbass department for sure. Midbass is quality in terms of being detailed, though there isn't as much quantity as there is compared to the subbass (I might not be holistic with this, my last IEM essentially attacks you with midbass) so you might not feel the midbass of the FLC 8S as much as you would feel its subbass. As others have said, low mids are not affected by the tuning components as far as I could hear (i.e. it didn't increase with the configurations I've tried, I guess its an intentional tuning to make the IEM sound more detailed and spacious?) so instruments like violins might be detailed, but not feel as full compared to a midbass elevated IEM (this was with my equipment, I have heard that this aspect improves with dedicated amplifiers so try that out if you have it!). Though I regard the sounds of the no nozzle filters configuration to be the signature highlight of the FLC 8S, the nozzle filters give flavors of sound that could better suit and enhance the music you listen to. Your primary choice of nozzle filter would thus likely be dependent on the frequency ranges that your music tend to produce and emphasise.

Blue Nozzle
Matches | Dark, enclosed, bass-heavy

Listening casually, focusing on other things.

I tested these out with the stock medium silicone tips (offers the most treble extension according to FLC).

| Destroys treble response and reduces the midrange considerably, but offers more bass rumble and presence. Good for having music sit in the background. |

Coming directly from no nozzle filter with the TX400 tips, the blue nozzle sounded immensely muffled in comparison. It sounded so bad initially that I relegated the blue nozzle from the blue container to one of the plastic accessory bags (where I'll likely not touch it ever again). The blue nozzle mimicked the sound of my 5+ years old Apple EarPods quite well (enclosed, filtered, though with incomparably better detail retrieval obviously) so there's that going for it. That sounds way too harsh, because it is (don't actually compare the Apple earbuds to the FLC 8S - the differences exist in parallel dimensions separated by infinity) - its intended to show the MASSIVE difference between the audio clarity of no nozzle filter and the blue nozzle. And I would assume that you're looking at the FLC 8S for its stunning brillance and tendency to make you react passionately to the music. It probably wouldn't be found with the blue nozzle.

With that said, after listening to various tracks for an extended period of time and getting mentally used to the sound, I did notice that they offer more bass and thump. If you manage to get used to the sound of the blue nozzle, then it will still sound good regardless as the technical prowess and tuning of the FLC 8S is phenomenal. The blue nozzle could be regarded as offering a more lounging friendly sound - if you don't focus and listen attentively, they might be good for relaxed listening or just having music sitting in the background while you do something else (might not work if you have a good seal increasing the sense of bass/going for isolation in loud environments). Though after listening with no nozzle filters, I can't imagine why anyone would want to use the blue nozzles, they don't exactly play to the FLC 8S's strengths. Regardless, its a nice option to have if you want to just relax without feeling moved by the sound of the FLC 8S at the best parts of a song.

For listening closely and for intending to use these as the primary filter though - if your music selection consists of something along the line of 60% bass, 30% mids and 10% treble (in every song you listen to), then the blue nozzle might sound good in enhancing the bass feel at the expense of everything else. Whether that would be worth it to you, well, you'll just have to try it and find out.

Who knows, you might enjoy feeling the music more than you do listening to it. If that's the case, the blue nozzle might be of use to you.

Green Nozzle
Matches | Airy, not vocal-oriented, clarity necessitated

Listening to the nimbility and gracefulness of orchestra.

| Quick and precise treble imaging. High amounts of detail at the high ends, amazing for piano. May produce very noticeable sibilance in vocal tracks depending on the bass filter combination used. |

With my previous bass-heavy V-shaped IEM (Degauss Labs Noir), orchestral tracks or anything that emphasises the piano sounded... not good. The boomy midbass contoured and muffled everything, reducing the ability to distinguish the notes of the piano, so everything sounded very muddy and 'samey' as far as orchestral tracks go. Experiencing the green nozzles of the FLC 8S have opened a new door for me in music. A good benchmark for audio clarity of piano would be the track 'Blink' by James Maloney. The piano here is VERY quick and absolutely demands precision and clarity in the higher ranges or else the presentation would be very bad. With a V-shaped sound signature, the piano sounded like a mushed blur. Absolutely no detail could be distinguished because it was so blurry. With the FLC 8S's Clear/Clear/Green combination, I could distinguish every piano note and realized that the piano was actually linearly moving up and down in notes rapidly - and I could hear all of those notes without extensive focus. That is the clarity that these nozzles offer. When I changed the clear cylinder midbass filter to the grey one, it became more difficult to discern the individual notes. So if I were to use the green nozzle, I would definitely only stick to the clear cylinder filter to make sure that the treble isn't reduced from the more open port. Any subbass filter should be fine here for the most part - I didn't notice those directly affecting the clarity of the piano as much as the midbass filters.

A downside of these filters however is the added sibilance and unnaturalness added to vocal tracks. Vocals started to sound like they came out of a cymbals sound mixer instead of an actual human being. 'Chase' in the track Fly Away by Krys Talk/Mendum (the track where I noticed the horrendous sibilance in my inital impression) becomes 'shayse' with the green nozzle. And this was with the small Comply TX400 with waxguard, which is known to reduce and harmonise the treble. I can't imagine how bad the sibilance would be with any other tips (actually, I can - refer to my initial impressions with the unnatural silicone treble blaster-err I mean stock silicone tips).

I also noticed that everything had less sound decay in general, because the treble would just move from one note to another quickly without really letting it fade away naturally (like the sounds coming from the dynamic driver, which sounded more natural). As such, this nozzle is definitely not 'main-use'-able unless your music selection consists mostly of vocaless tracks. Would the green nozzle be worth keeping around for changing? Again, that is up to you and whether you like treble or not. The green nozzle filters does not destroy the spaciousness of the music like the blue filter does (actually it could be seen as enhancing it slightly), but it does destroy any sense of naturalness if your music is particularly vocal heavy. All in all, the green nozzle filter is a nice option for those looking to enhance their piano listening experience. It has the potential to make orchestral imaging astonishingly wonderful.

Gold Nozzle
Matches | Smooth, intimate, sibilant recordings

The fullness of vocals.

Referred by many as 'liquid vocals', the gold nozzle pushes the emphasis towards the ~2 kHz range while reducing treble noticeably around 8 kHz (resulting in it eliminating sibilance really well). It helps with the finish of the vocals, making them sound more 'complete' in a sense. The tradeoff is that there can be a lesser sense of space because the vocal is closer to you (though imaging and soundstage is excellent like the other non-blue nozzles), but it's definitely not as enclosed as the blue nozzle.

This nozzle can help with tonality and naturalness for some because it smoothens out the sound while bringing vocals to the center stage. It offers a slightly more natural decay of sound compared to the black nozzle for example at the expense of treble details. Treble is definitely pushed back with the gold nozzle, so that is something to take into consideration. You won't feel like being surrounded by clouds with this nozzle, but rather you'd feel like you're comfortably on the ground, at the front seat of a live performance. The gold nozzle sets out what it aims to do really well, and should work well with all styles of vocal music.

In sacrificing some airyness (treble) for a smooth tonality, I can definitely see a lot of people enjoying this nozzle filter.

Black Nozzle
Matches | Neutral, most music, forwarded instruments

No particular emphasis on anything. Easeful reference balancing.

This nozzle is quite neat (literally). According to innerfidelity measurements, they roughly emphasise the ~1.3 kHz and ~9 kHz ranges, so they could help with providing a fuller sound at higher ranges (for reference, the green nozzle filters also emphasise these ranges). Actually, comparing the black nozzle and green nozzle frequency response graphs, you could say that the black nozzle filter is the more balanced version of the green nozzle. It is the filter with the second most amount of treble (roughly ~4 dB higher than gold nozzle it looks like) and as such you might notice slight sibilance on a few tracks (increasing midbass helps alleviate this). It can work very well for those looking for a more linear extension and sound. I can't really say much else about this nozzle however, because nothing really stands out in my tracks to me using this. Is that a good or a bad thing? You decide.

Grey | Grey | None
Matches | Everything

Clarity and reference sound comes to life.

This, to me is the absolute highlight of the FLC 8S's coherent tuning and preeminent midrange. To reiterate on what no nozzle does: "without the nozzle, the mids will be higher around 2K Hz - vocal is more forward, the treble will lessen at around 4~5K Hz". From my listening, some definitions and playing around with a music editing tool and increasing/decreasing those specific ranges, I've found that this gives the most spacious, yet complete sound of all the nozzles. Listening to 'Times Like These' by The Eden Project, the vocals are paramount, spacious and effortlessly clear while the entire track emanated energy that made me feel the need to move along with it. I hadn't realised that the chorus had more than one vocal sound (there's another layer of vocals, who could've guessed with that clear singing!) before listening to it with the FLC 8S. Likewise, the awesome 'Wake Up' sung by the same person sounds incredibly passionate with this configuration - I could hear them breathing in lows and highs (I could differentiate how they breathed for each word they spoke with the no nozzle filter) without any sense of sibilance. It really, really is amazing how clear these are. With experiences like these on a constant basis across all of my music, I knew immediately from early listening that these were absolutely worth the price point (and I would say even more! The pure silver upgrade cable is an option...) - these sound coherent on every genre that I listen to, from classical/orchestral or ambient (which tends to sound blurry and congested when there is too much bass and little midrange - the FLC 8S is revelatory for me here!) to EDM (tune the FLC 8S to lift the bass and hear the pumping adrenaline beat!). These genres of music could not be further apart in terms of sound signature and emphasis - EDM needing midbass and midrange while Ambient needing midrange, treble and reduced bass. With the right sound tuning of the FLC 8S, such as this one (you might find others depending on your equipment!), both sounds amazing without the need for an equalizer or anything similar (unlike the other IEMs I've listened to. Equalizer can't make those excessively exaggerated peaks found in non-neutral, boosted IEMs sound good, believe me I've tried). Using lossless files, this IEM is incredible in evoking the more subtle details of well-mastered tracks. What is yet amazing is that you can still improve the already awe-inspiring sound with some advanced tinkering and better amplifier combos (+ impedance adapter) as well as using an equalizer (though absolutely not needed!). The FLC 8S sounds amazing at low volumes, and even better with a good impedance adapter and source at higher volumes! Still hearing some treble standing out? Remove the cylinder midbass filter from the right ear piece of the FLC 8S and feel the music even more!

FLC Technology.jpg

"Clarity" and "legendary variety of sound"

I previously used the Degauss Labs Noir, a V-shaped hybrid (1 dynamic driver & 1 balanced armature) IEM with a midbass boost. I'll compare the Noir with the FLC 8S back and forth to describe what I mean by clarity and effortlessness, at least from the perspective of a non-super enthusiast. The Noir is by all means a good IEM, excellent for its goal of sounding energetic and impactful, but I do not even doubt for a second in saying that the FLC 8S offers (much) (but-I-wouldn't-say-that-the-Noirs-are-bad) greater clarity and detail retrieval - it's immensely obvious because the less pronounced details stand out and make an impression on you. For example, with the track Quasar by Michael FK you can hear subtle, multiple layers of airy voices throughout the entire track, effortlessly presented with the FLC 8S at medium volume while I have to increase the volume to loud to even hear the layered voices on the Noir. While this is partially due to the characteristic of the Noir in having a V-shaped sound signature with bass boost (the combination generally reduces the ability to pick up subtle details due to a recessed midrange), reducing the bass with an equaliser did not make hearing the details easier. You have to squint and listen closely to hear the details, and even at ear-destroying volumes the Noir does not resolve all the details that FLC 8S does so effortlessly. Swapping back and forth between the IEMs there are so many echoes and sounds that I have never heard before when quickly changing to the FLC 8S, such as the echoes of the speech found in Moonlight by Rameses B. Effortlessness also improves other aspects such as airyness - the airy treble in Porter Robinson's Sea Of Voices is so awesome, easy to listen to and clear! By 'detail' I mean the character of the sound, so for example while the Noir produces much more bass, the bass is just "bass" and sounds like what you'd typically expect. The FLC 8S is able to produce the same amount of bass at a greater level of detail, allowing you to discover new things each time you listen, which makes re-listening to your music fun and exciting. The nuances of tracks presents itself to me clearly and distinctively and does not need me to critically listen so that I may hear them.

Want to be mind-blown even further? Listen to

Red | Clear | None

and feel the clarity of sound!

It sounds absurd, but I actually feel moved listening to the FLC 8S even without the energetic tuning due to the sheer clarity and detail presented that I have never noticed before. Put simply, the music feels more 'alive' despite not presenting that exciting V-shaped sound that is highly popular among IEMs currently. It's an incredible hallmark of high fidelity audio that makes pursuing music truly rewarding, and the FLC 8S offers this astronomical leap more seen in $1000+ headphones at a $350 price point. It's astonishing what FLC have accomplished as a new company with the 8S - they didn't just make an amazing in-ear monitor that surpasses the typical downfalls and flaws, they made one that could potentially sound like 5 distinct IEMs (and potentially much more if you're crafty) for the price of one, with its own breathtakingly beautiful midrange character. The FLC 8S doesn't just stand out, it shines with the face of a thousand suns, and should be the premier headphone recommendation for those looking to take a flexible and unregrettable step into higher fidelity sound. For some, it could be their last pick for the foreseeable future of driver-based headphones, and in which case I can definitely see why. The FLC 8S is the most versatile headphone out there right now, and its clarity, resolution and uniqueness could be appreciated for decades to come.


Headphoneus Supremus
Pros: great build , filter options for all tastes on top of a great base IEM underneath it., some of the best resolution and imaging I've heard
Cons: Default cable could be way better, coupling of mid and high filter limits some tuning options and no tuning of lower mids occurs regardless of filter combination.
I was loaned the FLC8s to audition before purchasing the b400 or LZ A4. I did not cover un-boxing or the accessory kit as I received the product without the box and with filters already mounted. I'd like to thank @Ngoshawk for graciously loaning me the FLC8s to try. I'll admit, I really don't want to return them but will have to buy my own soon.

The 8s by FLC is a smaller than average uniquely shaped iem designed for over ear wear. The housing is all plastic which may turn some people off, but seems well enough put together. At first glance, I thought they might be colored aluminum shells due to the fit and finish. The housing feel solid and seams fit well with no obvious gaps or mis-alignments. I saw no weak points in the shell that I would worry about coming apart over time. The fact that 3 different filters fit into these small housings means that any slight misalignment or wobble during production and everything fails to work correctly. Filters themselves are tiny and with these being on loan, I was very weary of potentially losing one. Once attached, they stay solidly in place so no worries during use of the 8s but when changing filters, it can be a challenge for aging eyes and clumsy fingers.

The best news for me was that the 8s arrived with the upgrade cable already in place so I avoided use of the stock cable except to do some sound comparisons as Ngoshawk requested my thoughts on the cables. The stock cable is overly stiff and combined with my glasses was an uncomfortable fit. Were I to purchase the 8s, I would have to buy the upgrade cable as the option to go without glasses or without music is simply not appealing as both seem rather necessary. The upgrade cable still has a bit of memory and isn’t the most pliable cable but does make a vast improvement in comfort for me. Although I am reluctant to attribute any auditory changes to a cable, the silver single crystal cable did seem to make a bit of improvement particularly in the low end. The cables use the 2 pin UE connector type making it a little more difficult to find replacement cables and those who prefer a more supple cable will certainly have to do some looking at aftermarket options.

Stock Cable

Upgrade Cable

Fit and Isolation
The shape of the 8s combined with its lightweight and smooth surfaces made it very comfortable to wear although the nozzles do not have a forward angle as some other earphones do and may cause some problems with fit for those with small ear canals. For me, they fit well and when paired with symbios tips the seal was good although a bit shallow. With the ports in the earphone itself and the shallow fit, I can only describe the isolation as mediocre. If I had to guess, I’d say somewhere around a -12dB reduction of outside noise.


This is the hardest part of this review by far. The fact is: the 8s sounds like whatever you want it to. The filters really do work, you can tune the 8s to be a bass cannon if that is your thing, or head the other direction and create an absolute treble knife. Most will probably tune the 8s somewhere between those extremes and with 36 possible combinations a lot of middle ground exists. I’ve tried to make notes about the driver characteristics that come through regardless of how you adjust as well as notes on specific filters where they have a noteworthy impact.

In order to understand the sound options, you have to understand the filters. The inner port on the shell tunes the sub-bass frequencies, the outer port tunes the bass frequencies, and the screw in nozzles control the mid and high frequency response. The filters come packaged in an aluminum tube with a key ring adapter. This is misleading as changing filters on the go is certainly not recommended as the parts are tiny and the operations are tedious. I recommend changing filters only on a large flat surface (preferably light colored where the filters don’t blend in) with good lighting and perhaps a razor blade and set of angled needle nose pliers as the provided tweezers are less than helpful. Using a scalpel blade to get under the edge of the filters and lift is much easier than trying to get enough surface area exposed to use the tweezers. The housing ports are all pressure fit, so pushing the filters in requires precise orientation and gentle pressure. The nozzle filters are larger, screw-in and much easier to work with.
inner filter.JPG

The following were things that I noted regarding the 8s regardless of which set of filters were installed. First and foremost, for a hybrid BA/dynamic, the 8s has better coherency than most. Unlike some hybrids, I would be hard pressed to tell you which frequencies were being produced by which driver in the 8s. Extension is great at the top end and good at the bottom. These have no large roll-off at either end of the spectrum. It didn’t appear to me that the lower mids were changed at all by the tuning filters. The upper mids and high frequencies were quite obviously shaped by the nozzle filters but if the lower mids were moved at all it so slight as to be imperceptible to me. Lastly, the level of detail and micro-details were better than expected and would have made me guess this was a more expensive headphone had I not known the price going in. Overall, I would say the 8s retains a slightly bright signature regardless of which filter set you choose.

The low-end is shaped by both the sub-bass filter and the bass filter and I found that I enjoyed the red sub-bass filters but needed to back off the bass filter by one level as the bass got a bit boomy and lost a bit of control when wide open. Stepping back a notch to the black filter did lose a bit of quantity, but gained a lot of quality so it was a trade well made. Overall, the sub-bass extension was better than I thought possible out of a 6.4mm driver and the bass was well rendered unless the wide open (filter less) setting was used. I would have liked to see a bit more bass quantity but not at the expense of quality. If you are a bass-head, this is probably not the earphone for you as it trades quality for quantity when you try and increase the bass in a way that is not pleasing.

as noted the lower mids are not shaped by any of the filters so you have less options here. The good news is I didn’t hear a pronounced mid-bass hump and any bleed into the lower mids was very minimal. Instrument separation is good and male vocals are lifelike and ever so slightly forward. The upper mids are much more tunable with the filters and my favorite was a slightly bright filter that lifted female vocals a bit and brought a bit of extra air to the top end. I spent quite a bit of time trying the green and black bores, which are either medium mid and most high frequency or medium mid and high respectively. I came to the conclusion that depending on the track, I could continually swap these two filters and never resolve a single filter that I liked best so I settled on the black as a compromise.

having just said I settled for the medium high frequency filter, I really enjoyed the sparkle and air the green filter brought to the table and with all but the most sibilant of tracks the green filter really did bring more life to the sound signature. For some reason though, I found the green filter a big more fatiguing than the black which dialed it back a notch. I tried to go without a filter as some recommended but found that was extremely fatiguing unless I dialed back the 6kHz and 8kHz by about 6dB.

Truth be told, none of the mid/high filters were exactly the combination I would have liked and a little EQ combined with the green was my best fit. If using a player that didn’t have EQ, the black was the best compromise.


I found the 8s to have a very wide soundstage if not quite as deep as it was wide. Imaging was good with instrument placement easily visualized and movement of singers on stage in live performance well rendered. The 8s is easily one of the best in-ears I have had a chance to audition when considering imaging and I suspect this is one category where the 8s punches well above its weight as I have had the opportunity to audition several other IEMs in this price range and none come close.

The FLC8s is one of the best IEMs I have had the pleasure to audition in quite a while. Admittedly, I usually shy from auditioning things too far out of my price range, so I cannot make the direct comparisons to flagship IEMs that I am sure others will. I can say that without any tuning tricks, the 8s is one of the best IEMs I have heard for coherency and performs with a natural ease to its sound that I haven’t seen in this price range before. With the filters, the tuning options open doors to all kinds of signatures. While I would love to see them decouple the mid and high filters to give even more tuning options, I have to say I was not displeased at all with Red, black, Green or red, black, black. Both of those cater to my tastes with good sub-bass, controlled bass, no bleed over into the mids and nice forward upper mids and treble. This takes an already good voice and tailors it nicely to my personal tastes. Give the FLC 8s a try and I’m sure you can find at least one combination of filters that suits your style too. As for me, now I have to find my own pair so I can return these to their owner who is already regretting being without them for 2 weeks while I had them. Thanks again to @Ngoshawk for introducing me to such a great IEM.


Which one are your sources for these IEM (DAP, smartphones..)?
They work well from my Cayin N3 DAP which is lower powered than most or my HTC m9 smartphone. I do think they open up a little more with more power but they certainly can be used without an amp and not miss much.
Pros: Professional fit and sound, Filters designed to shape all frequency ranges (36 different tunings), Nice accessories package
Cons: Cable is stiff with lots of spring and memory, Changing the low frequency filters is tedious
At the time this review was written the FLC 8S was listed for sale on Amazon and Musicteck’s website. Here are links for more information and purchase.
I’ve been around the headphone scene long enough to have my doubts about companies pushing their “new technology” products. I say this because often times it’s a gimmick to get you to buy something new. “Revolutionary sound damping technology” can be a company’s creative way of saying they put a layer of wool or paper over their drivers to dampen the high frequencies. Don’t be fooled by a lot of the mumbo jumbo. Do your homework and most importantly buy what you think sounds best, and at a price you’re comfortable paying.
When it comes to tuning earphones manufacturers start with a driver and enclosure, then change the amount of air that flows on each side of the driver. That, or they add dampers to control how much of each frequency makes it to the listener’s ear. While I’ve seen many earphones that come with tuning filters I haven’t seen much out there that allows the owner to shape the sound from top to bottom.
Most filters are nozzle replacements that control the upper mid-range and high frequencies. Although that’s an effective and fun product, often time owners come up short of what they consider the most ideal sound for their exact preferences. By the time something goes mainstream we’re often times already thinking about what we want next. This applies to the concept of sound shaping as well.
When I was a young there was very popular literature amongst my childhood peers called “choose your own adventure” books. The decisions you made while reading them determined the pages you would read next. The result was a book whose story changed and depended on what we wanted to choose. The added element of choice made reading them a lot more fun.
About a year ago the FLC brought to market a “choose your own adventure” earphone. Instead of one set of interchangeable nozzle filters, the 8S has three different ports to adjust sound. Many of my fellow Head-Fiers who heard them raved about the product. Although I didn’t have a chance to try them until recently, I trusted the impressions of those who did and kept them on my review radar. The main question that remained for me was just how effective the filter system was in terms of changing each frequency.
When Musicteck contacted me to see if I was interested in reviewing the 8S I jumped on the chance. The main reasons were to see what the hype was all about, and also see if the filter system worked as advertised. If FLC was able to shape the entire spectrum of sound, the next big thing in in-ear monitors is already here. Let’s find out if FLC accomplished this and go over them with a comprehensive review.
I was given a free review sample of the FLC 8S in exchange for my honest opinion and review. I am in no way affiliated with FLC. I’d like to personally thank Andrew for the opportunity, and allowing me to share my honest and unbiased opinion with the Head-Fi community.
The FLC 8S comes in a light brown box with silver accents. Not a lot to say here…
A magnetized tab flips open to reveal the earphones resting in a custom foam inlay. From that point various tabs cleverly open to reveal the accessories. The uniquely designed box leaves owners thinking they’re in for a real treat. If they can package them this clever, the earphones must be fancy too, right?
Specifications and Accessories
Driver unit: 8.6 mm dynamic drivers+ dual balanced armatures
Rated Impedance: 11 Ohm
Sensitivity: 107 dB/mW
Frequency response: 20Hz- 20KHz
Plug: 3.5mm gold-plated plug
Cable: 1.30 mm TPU cable
1X Pair of FLC 8S earphone
1X Modular earphone cable with 0.75 mm two pin connection
8X Pairs of silicon tips (S,M,L)
1X Metal hard case
1X Pair tweezers
1X filter tuning set and metal carrying case (multiple tuning filters with extras)
1X Airline adapter
1X ¼ inch adapter
Build and Design
The 8S housings appear to be made of uniquely shaped high density plastic. The housings seem to be very durable and I don’t see there being any weak points. The shape is set up for an over the ear fit. A rubber filter can be seen on the inner and outer parts of the housings. The first thing I thought when looking at the filters is “wow, these are tiny!” Another filter can be seen screwed into the nozzle. Overall I’m happy with the shape. The FLC 8S comes in two colors, midnight teal and red.
Holding them in my hand, the first thing I notice is that the cable is stiff, almost too stiff. There’s lots of spring and memory. I took a look at the owner’s manual and it states that the cable is specially designed for the FLC 8S, has quality innards and they encourage that owners don’t remove and replace the cable. Because of this I didn’t mess around too much with it. Although the cable has a considerable amount of spring and memory it’s not the worst I’ve seen and the included chin and neck slider helps snug things into place. The angled two pin connection looks like it will help with ergonomics. The 8S has a ninety degree angled plug with a 3.5mm jack. Strain reliefs seem reliable and strong. There is no microphone or remote, but the modular cable makes this a possible upgrade for owners looking to do so.
Ergonomics, Fit & Isolation
The FLC 8S provides a very good over the ear fit. Once you find the right tip, the earphones can be popped in, looped over the ear and snugged into place with the included chin/neck slider. I could wear the 8S for an extended period of time without needing to readjust the fit. The included tips provide a relatively shallow fit and are a softer silicone material with a wide bore. Tip rolling was relatively easy to do thanks to the fairly standard nozzle size. On a whole, isolation is average and depends on what filter you use. I could hear ambient noises, but they were eliminated once music was playing.

Now to the good stuff…
The 8S filter system works. Yes it works, but I don’t consider it a perfect system.
There are three ports. The inner port of the housing shells tunes the earphones lowest “ultra low” frequencies (sub bass). The outer housing port controls bass tones above the lowest frequencies. There are metal pins that screw into the nozzles that control the mid-range and high frequencies. Although the system works pretty decently, I do wish the three filter tuning was split differently and into thirds (lows, mids, highs). Still, it’s not a big deal because the FLC accomplishes the same thing but in a unique and different way than I’d prefer.
The filter system is stored in a blue metal canister that attaches to a key ring. Although I can see some people taking the filter system with them by attaching it to their keys, I don’t consider this filter system ultra portable, and definitely not something you can switch out on the go.
To change the filters I strongly suggest you change them on a counter, under good lighting, take your time and be very careful. The biggest gripe I have about the FLC 8S is that the lower frequency filters that attach to the housings are TINY and tedious to change. You can easily lose (or break) these filters if you aren’t careful. Because of this, the 8S comes with one extra of each of the lower frequency filters (in a ziplock bag). Although the 8S comes with a pair of tweezers to help with the process of changing the filters, I didn’t find it very useful. I would suggest you keep a little extra slack on your fingernails and carefully use them to pry and place the filters how and where you want.
The lower frequency filters are made of rubber and appear to have damping materials on the inner parts of them. The filters are pressed into the corresponding holes and are securely held in place with pressure placed upon the rubber tubes from the diameter of the holes of the housings. These filters control the amount of porting to the dynamic driver, altering the earphones’ bass response.
The midrange and treble are adjusted by unscrewing and screwing various metal pins into the 8S housings. I really enjoyed using these filters. They were very easy to switch out. Moving forward, I hope FLC incorporates this threaded option to the other frequencies it will be an improvement.
With all this said, the beauty of the FLC 8S is that it does exactly what it says it does. I can shape the sound to be ideal. After weeks of trial, error and comparisons I’ve found my favorite filter system. Let’s discuss this more in the sound portion of the review.
Don't take just my word for it. Forrest, the man who invented these earphones has made a video describing the incredible technology these things have. Here it is:

Source Matching
The 8S comes in at 11 Ohms and 107dB of sensitivity. That is pretty sensitive and doesn’t require more than a phone or portable DAP in low gain. Although they will work with desktop gear, I didn’t get any noticeable benefit from added amplification. If you want to improve the sound of these earphones beyond the tuning filters, focus on using higher quality recordings and increased bit rate music files.
The 8S sounded awesome with my LG V20 and iFi micro iDSD. Honestly, the 8S works with all of my portable sources. If something sounded like it could use something, it was a matter of changing filters to accomplish what I was looking for.
Sound Review
Because there are 36 different tuning options I can’t go over each one without writing a book about them. Instead I’ll share my experience with them and what I found to be my favorite filter combination.
Putting into considerations the multiple tuning configurations, FLC has taken out some of the leg work by listing some recommended filter combos in the owner’s manual. They’ve also nailed it in terms of describing each of the filter combinations. I honestly couldn’t describe it any better than they have. You can try to come up with a better filter combination than what FLC recommends, but after trying just about every filter combination I came to the conclusion that FLC has identified and highlighted the best ones of the bunch.
Switching the “ultra low” and “bass” filters is tedious. Here’s a tip, go with the recommended filter combos first. Once you’ve done this you will have a feel for what each filter offers, then be able to tweak it to your preference if you need to. If you don’t have the hands and coordination of a surgeon, you’ll be better off changing the lower frequency filters as little as possible. At this point I’m just glad I haven’t lost any yet.
I got flustered changing the filters and putting the unused filters back in the carrying case, at which point I decided to find the combination I like best and haven’t looked back. The “balanced” combination is my favorite, and offers a very even tuning from top to bottom.
The good news is that once you find your favorite filter combination, these are some of the best sounding hybrid in ear monitors I’ve heard. There is enough variance in the sound filters to say I’m confident just about everyone will come up with something they find ideal (or very, very close). If your preference changes a bit over time, there is a sound tweaking tool kit waiting for you.
The FLC 8S covers every frequency from the lowest of lows to the highest of highs. Although the mid/high frequency filters aren’t ideal tools for tweaking each sound one by one, you can use various filter combinations in conjunction with them to make it work. Yes, FLC has given me the power to shape sound from top to bottom, and that’s awesome! To add to this, the separation of sounds is great. Detail is top of the line, and extension is great in both directions.
Comparison to the LZ-A4 ($199 USD on many sites)
The FLC 8S has a direct competitor and it’s the LZ-A4. The A4 came after the 8S and made some interesting tweaks. It’s a three way hybrid (just like the 8S) and comes with tuning filters that adjust the lower, middle and higher frequencies.
Comparing the two, LZ has done some things that trumps the 8S. The housing shape promotes both and under and over the ear fit and the cable is much more manageable and easy to use. LZ has incorporated a MMCX connection as compared to the two pin connection of the 8S (you pick which one you like more). A big plus for the LZ-A4 is that the tuning system is much easier to use than the FLC 8S. I am more apt to changing the filters on the go. Build quality on both is about the same.
With all that said you may be wondering why people would still consider the 8S. I personally feel that the 8S justifies its asking price over the A4 in a few ways including where it matters most, SOUND. The A4 sounds great, but the 8S gives me more control of the frequency response. The filters (although a PITA to use) are more precise, like precision tools used to perfect the sound to my liking. Simply put, when it comes to sound I can dial it in better with the 8S as compared to the A4. Also, the entire package of the 8S from materials and design to accessories is more professional and less generic than the A4. The A4 may be more fun and easy to use, but the 8S has superior fidelity.
With the A4 I can adjust the bass three ways. With the 8S I can adjust it nine ways. For the most part the bass of the A4 lingers and decays slower than the 8S (with preferred filter combos). Compared to my ideal filter combination with the 8S, the A4 bass is a bit more sluggish in comparison. After my ears adjust to the 8S tuning, the sound is more natural and with more air between instruments and vocals. When my ears adjust to the A4 it seems to have more musicality and a more consumer friendly tuning. You won’t go wrong with either, but if maximizing fidelity is most important to you, I strongly suggest the 8S.
The tuning filters of the 8S are not a gimmick, they’re the real deal and do exactly what they say they can. I can achieve just about any sound signature I want with them, and that’s awesome! At this time I can’t think of another product that gives the owner the ability to adjust and fine tune the sound at this level (at any price). The 8S has a professional fit and premium package of accessories. These will work as a reference monitor for professional musicians, as a earphone for audiophiles who want to maximize their music experience, and for casual music listeners who want to take their listening experience to the next level. They are a design (and price) that caters and appeals to several different markets.
There are some things that could be more ideal. The bass tuning filters are tiny and it’s tedious to change them. The cable is stiff and has a lot of spring and memory. The good news is that once you’ve found the right filter combination and put them on, both of these things become a non-issue. The fact that I can take the 8S and make the earphone sound exactly how I want it to, I can overlook these two things. At the end of the day it’s all about sound for me. The 8S not only delivers high quality sound, it does it with an ideal tuning for my preference.
When rating a product I have to take all criteria into account (including price). The FLC 8S gets four and half stars for build and design, four and a half stars for ergonomics, three and a half stars for functionality (springy cable and changing filters is a pain), and FIVE BIG STARS for sound. They are the current king when it comes to shaping sound.
Thanks for reading and happy listening!
Great Review. Didn't notice them listed in your profile but have you had a chance to compare these, to the iBasso IT03?
I haven't heard the iBasso IT03. Sorry buddy.
There was a fair question about whether these can be considered as near TOTL. My take; with certain tunings these sure sound like TOTL units.

I feel they are more comfortable and easier to fit than the IT03. Your mileage is sure to vary.


500+ Head-Fier
Pros: Incredible imaging; clarity and resolution; Tuning options
Cons: That cable; small tuning filters

Over the course of this year, I have noticed that my enthusiasm about buying new gear has become rather stagnant. Ever since I started my personal audio-journey in 2014 and many listening sessions later, nothing excites my now veteran ears anymore. To my surprise came FORREST and renewed my childish side with their announcement of the FLC8s. I have been following the FLC8 Thread for quite some time now. And while the FLC8s are available since November 2015, I never pulled the trigger. Until now...

Enter FLC8s by FORREST.

Disclaimer: I bought these on Shenzhen Audio for 269$. I'm not affiliated with FORREST or Shenzhen Audio in any shape or form.

About me:
My name is Noel aka. FUYU, I'm 19 years old and an avid lover for everything technical.
While everything is subjective, I like to explain in more rational enclosure with graphs and technical prowess. I care about facts and only facts, meaning no fancy 300$ cables and value by price-to performance.


  • Type: Hybrid dual BA + 8.6mm Dynamic Driver
  • Frequency Range: 20 Hz – 20 kHz
  • Impedance: 11 ohm
  • Sensitivity: 117 dB @ 1kHz 1mW
  • Cable: 1.2m 4 core single twisted copper (replaceable)
  • Jack: 3.5mm gold plated, straight jack
  • Weight: Approx 14g with tips in place
  • IEM Shell: Hi-gloss strengthened plastic


IMG_20161114_141112.jpg IMG_20161114_141236.jpg

IMG_20161114_142133.jpg IMG_20161114_152811.jpg

The FLC8s comes in a rather large box for an IEM. Don't be fooled however! This is not due to the IEM itself, but the quite stellar set of equipment and its very unique presentation. Using a folding mechanism reveals two compartments, both protected in thick blue coloured foam. The first layer contains the IEM, while the second layer retains the carrying case and filters with included tweezers. A+ FORREST!

The included metal carrying case, while not so transportable, will protect your FLC8s or IEM of choice against all kinds of hazards. That thing is literally undestroyable. Reminds me of those old Nokia Cellphones back in the day...

Opening up the carrying case reveals an airline adapter, a 3.5mm to 5.3mm adapter, a cleaning tool coupled with some tips. Everything you need.

The filter case is likewise solidly built and comprises a capsule with screw on top, and inside is a mould which has enough room to house 3 pairs of tuning bores, and 2 pairs of each of the ULF and LF tuning plugs.

Build and Design:


The FLC8S is made in a high gloss plastic shell, and at first glance you'd think it was made of polished coloured aluminium. Each earpiece is very ergonomic – designed to fit the contours of the ears, without feeling heavy or having sharp edges. The two piece plastic shell looks very sophisticated, coming in either blue or red colour.

Dimensions are on the moderate side with 18mm x 10mm x 18mm. The body is S-shaped, and the nozzle is perpendicular to the main body. I didn't encounter any major issues with fit, but I can envision it not being ideal for everybody's ear-type. Although it is a vented design (replaceable nonetheless), Isolation is actually above average for most In-Ear designs. Commuting is very acceptable with some adjustment to your listening volume.

The biggest shortcoming of the FLC8s is the included cable. While it has lost the big 7,5cm chunk of memory wire in newer revisions, it is still rather unruly and tangles a lot. Furthermore it has in probable amounts of microphonics, making it unsuited for heavy-duty activity.

Luckily the FLC8s features a very stable 2-pin connection. The sockets are raised, with the cable plugs fitting snugly over the top for added strength. The FLC8s uses the UE standard.


Filters - Usability and general Impressions:

The filters are divided in to three brackets:

  • ULF - Ultra-Low-Frequency - Sub-Bass
  • LF - Low-Frequency - Mid-Bass
  • MF/HF - Mid and High Frequency

The experience which defined my time with the FLC8s. I love tinkering with things, but my fingers are pretty large (I can easily palm a Size 7 Basketball). The MF/HF filters are easy to replace by unscrewing them from the nozzle. However, inserting and removing the ULF/LF filters was frustrating and took lots of fiddling and patience. I even lost a black LF filter to the carpet - beware!


(For some proper measurements please refer to Brooko's review here)

General observations:

  • Clean sounding with lots of micro-detail
  • Imaging is precise and with good airiness
  • Coherence is fantastic even with Red-Black filters in place
  • No glaring sonic weakness
  • Lower midrange is not affected by tuning
  • Extension on either side of the spectrum is fantastic

Don't expect the FLC8s to be the jack-of-all-trades. It has a base signature which is retained over all filter combinations: A bright, but organic sounding In-Ear. It is not going to sound warm or even bassy. Think of it this way:

The FLC8s is not a tunable IEM with great sound. The FLC8s is a great sounding IEM with tuning options.


  • 11Ohm and 114dB/mW makes for easy listening out of your smartphone
  • Amping is absolutely not required
  • The FLC8s profits from warmer sources

Some Filters combinations:



The RCG combo is my personal favorite and suits my preferences best with its slight U-Shape signature:


  • Overall very balanced sounding with some slight tilt towards the lower echelons adding some rumble to the mix.
  • Neutral sounding mid-bass. Zero bass-bleed into the midrange.
  • Highly detailed bass response, good texture.


  • Lower Midrange is slightly recessed, thus improves the spacial presentation.
  • Organic sounding with some moderate brightness.
  • Soundstage is moderately sized in all three directions. Appears spherical with center position.


  • 5kHz area is slightly recessed.
  • Moderate rise around 7kHz, giving the FLC8s some sparkle without getting fatiguing


The RGG combo was the first combination I have listened to. I don't enjoy the Gold filters all that much. The RGG variant works well with modern genres.


  • Overall more impact with extra energy
  • Focus on Mid-Bass. Plenty of bass. Although Bass-Heads might be left wanting.
  • Retains the same clarity and coherence.


  • More upper-mid focus around 3kHz compared to the Grey filters
  • Forward sounding female-vocals
  • Soundstage appears to be smaller
  • Overall brighter sounding


  • Identical sounding, but balance has shifted.
  • Loses some airiness.
  • Detail retrival is the same.

The green and blue filters are too extreme for my tastes. The former is too peaky in the 7kHz area , whereas the latter sounds too muted and rolled off. I can safely say that the FLC8s works with almost any genre and excels with classic in particular.

Comparison with the Trinity Phantom Master 4:

The Master 4 is overall warmer and more inviting sounding compared to the FLC8s. The FLC8s is less spacious sounding, but more precise in terms of imaging. Bass is much more evident on the PM4, with authority which simply cannot be matched by the FLC8s, albeit at the cost of sounding slighly bloated. Instruments are easier to depict with the FLC8s. Furthermore due to the smaller soundstage, the FLC8s has an easier time diving into the individual aspects of songs and music. The FLC8s has better detail-retrieval overall. The PM4 has more mid-bass and lower midrange emphasis, which makes it warmer and more "fun", whereas the FLC8s is generally more neutral and linear in presentation. My personal preference goes to the FLC8s. The PM4 has too many sonic weaknesses compared to the FLC8s, in particular in the upper-midrange to treble area. FORRESTs offering has better realism, more linearity and more technicality.

Final Words:

I really enjoy the FLC8s. For around 300$, you get an all-around package, which will keep you up at night for many months to come. While it is not perfect, the versatility you get for the asking price is well worth it. Flcforrestwei good job! Looking forward to the Celeste.
Good review! Thanks!
Congrats on another good review.
Looking forward to read your take on those PM4 by Trinity...
This is a great review. Thanks!
Pros: Versatility in tuning, comfort, clarity and resolution, bass quality and speed
Cons: Microphonic tangly cable, tuning parts very small + easy to break/lose, tweezers are useless, mid-range limited tuning with existing filters/bores
For larger views of the photos (1200 x 800) - please click on the individual images


The FLC8S was one of those IEMs which burst onto the scene with practically no warning, and before I knew it, had become very popular with a very loyal and vocal fan base. I wanted to try them for the purposes of a review (to see if the tuning did indeed live up to the hype) – but I've had a policy of not soliciting review samples for a while now (preferring vendors to approach me). Some may think this strange, but in my own way I find it easier to be objective if I have no obligation to the manufacturer. Lets just call it one of my quirks.
So my thanks for the opportunity to review the FLC8S go out first and foremost to Forrest Wei for approaching me, and sending the sample, and second to Djscope and nmatheis for both contacting Forrest and recommending me. I really appreciated the chance to hear them.
Finding a lot of information about the Company is pretty difficult – Google didn't turn up a lot of hits – just a lot of very positive reviews about their products (always a good sign). So for the most part the following is taken from a number of different websites and also some info about Forrest borrowed from Nik's very good review. FLC really is based around Forrest Wei's mastery of tuning and design – and his list of credentials is very impressive. Over the years, he has worked at companies including Ultimate Ears, Harmon and Jabra – and been heavily involved in designing and tuning both universal and custom in-ear monitors. Anyone who's heard the Oriveti Primacy will possibly also recognise some of his tuning in that earphone as well (distinctive 1-2 kHz bump). One of Forrest's goals has been to sell an affordable IEM with enough tuning options to give the user the ultimate choice in the final signature. This goal was realised with the release of the FLC8S I'm reviewing today.
The FLC8S that I’m reviewing today was provided to me gratis as a review sample. I have made it clear to FLC that I still regard any product they send me as their sole property and available for return any time at their request. But I thank them for the ability to continue use of the FLC8S for follow up comparisons. I do not make any financial gain from this review – it is has been written simply as my way of providing feedback both to the Head-Fi community and also FLC themselves. I do acknowledge that t is extremely unlikely that FLC will ask for the IEM to be returned, so for all intents and purposes it is provided freely.
I have now had the FLC8S since February. The retail price at time of review is USD 360.00 (Lend me UR Ears), or USD 340.00 (Shenzhen Audio)
I'm a 49 year old music lover. I don't say audiophile – I just love my music. Over the last couple of years, I have slowly changed from cheaper listening set-ups to my current set-up. I vary my listening from portables (including the FiiO X5ii, X3ii, X7, LP5 Pro and L3, and iPhone 5S) to my desk-top's set-up (PC > USB > iFi iDSD). I also use a portable set-up at work – usually either X3ii/X7/L3 > HP, or PC > E17K > HP. My main full sized headphones at the time of writing are the Beyerdynamic T1, Sennheiser HD600 & HD630VB, and AKG K553. Most of my portable listening is done with IEMs, and lately it has mainly been with the Jays q-Jays, Alclair Curve2 and Adel U6. A full list of the gear I have owned (past and present is listed in my Head-Fi profile).
I have very eclectic music tastes listening to a variety from classical/opera and jazz, to grunge and general rock. I listen to a lot of blues, jazz, folk music, classic rock, indie and alternative rock. I am particularly fond of female vocals. I generally tend toward cans that are relatively neutral/balanced, but I do have a fondness for clarity, and suspect I might have slight ‘treble-head’ preferences. I am not treble sensitive (at all), and in the past have really enjoyed headphones like the K701, SR325i, and of course the T1 and DT880. I have a specific sensitivity to the 2-3 kHz frequency area (most humans do) but my sensitivity is particularly strong, and I tend to like a relatively flat mid-range with slight elevation in the upper-mids around this area.
I have extensively tested myself (ABX) and I find aac256 or higher to be completely transparent. I do use exclusively red-book 16/44.1 if space is not an issue. All of my music is legally purchased (mostly CD – the rest FLAC purchased on-line). I tend to be sceptical about audiophile ‘claims’, don’t generally believe in burn-in, have never heard a difference with different cables, and would rather test myself blind on perceived differences. I am not a ‘golden eared listener’. I suffer from mild tinnitus, and at 49, my hearing is less than perfect (it only extends to around 14 kHz nowadays).
For the purposes of this review - I mainly used the FLC8S straight from the headphone-out socket of my FiiO X3ii + E17K and/or X3ii + IMS Hybrid Valve Amp , and also used (at different times) my iPhone 5S, and a variety of the other DAPs I have around me. Although I tested them with an amplifier, I do not think they benefit from additional amplification (I use mine mainly for consistency when reviewing and also to extend battery life on the X3ii). In the time I have spent with the FLC8S, I have noticed no changes in the overall sonic presentation, but am aware that I am also becoming more used to the signature of the FLC8S as I use them more often (brain burn-in).
This is a purely subjective review - my gear, my ears, and my experience. Please take it all with a grain of salt - especially if it does not match your own experience.


The FLC8S arrived in one of the most unique boxes I've come across in over 100 audio reviews. At first glance it looks like a beige rectangular cube – sort of like an outer shipping box – measuring approx 160 x 130 x 90 mm. It has the FLC logo on the top and sides, and the simple description “Hybrid Headset”.
The quite plain looking box
Top lid flipped open to reveal the FLC8S
Pressing down on the foam reveals a hidden compartment
At the bottom left of the front face is a simple instruction to “open here”. Lifting this cover reveals the FLC8S safely nestles in a form-fitting blue foam top section. On the foam is neatly labeled “press here” - and this reveals a second small compartment holding the tweezers and cable. OK – I was a bit lost, what about the accessories and filters? Then I noticed the bottom left again – once again telling me to “open here”. This revealed there was an upper tray and lower tray – with the lower tray opening like an older style jewellery box. The bottom tray housed the instruction manual, case (which holds the tips and other accessories), and the clever filter holder.
The original foam layer flipped to reveal cable
Box opened right out to reveal lower cavity
Bottom cavity holding case and filter holder
The entire package is incredibly comprehensive and includes:
  1. The FLC8S
  2. The metal alloy screw top carry case
  3. The metal alloy filter holder (also screw top)
  4. 4 sets of clear silicone tips (L, M S, VS)
  5. 4 sets of black silicone tips (L, M S, VS)
  6. 1 4-core replaceable cable (twisted)
  7. 1 cleaning tool
  8. 1 airline adaptor
  9. 1 3.5-6.3 mm adaptor
  10. 3 pairs ULF tuning plugs (with a couple of spares)
  11. 3 pairs LF tuning plugs (with a couple of spares)\
  12. 4 pairs MF/HF tuning bores
All the accessories
The very sturdy FLC8S case
Case top (you can just make out the subtle FLC etching
The carry case is incredibly solid, and quite large – 80mm diameter and just under 40mm in height – so it is more transportable than portable (not really pants pocket friendly), but it is perfect for protection and I've used it a lot for transport between home and work. It is nicely lined with soft felt for protection.
The filter case is likewise solidly built and comprises a capsule with screw on top, and inside is a mould which has enough room to house 3 pairs of tuning bores, and 2 pairs of each of the ULF and LF tuning plugs. For most people this is ideal, as they'll have the others fitted on the FLC8S – but when we come to the tuning section I'll explain why I would have personally liked room for another couple.
Tip selection
Very good FCL manual (more on that later)
The filter holder / fob.
Overall – the packaging is unique, very comprehensive, and looks like it covers everything you're likely to need.
(From FLC)
Hybrid dual BA + 8.6mm Dynamic Driver
Frequency Range
20 Hz – 20 kHz
11 ohm
117 dB @ 1kHz 1mW
1.2m 4 core single twisted copper (replaceable)
3.5mm gold plated, straight jack
Approx 14g with tips in place
IEM Shell
Hi-gloss strengthened plastic
The FLC8S is made in either high gloss blue or high gloss red, and at first glance you'd think it was made of polished coloured aluminium. But once you have it in your hand, the extremely light weight and feel confirms it is actually a moulded two piece plastic shell. Each earpiece is very ergonomic – designed to fit the contours of the ears, and it is clear that Forrest has taken great pains to ensure the shell is well rounded and without sharp edges.
Shell showing the 3 filter placement choices
Side view back and front - showing nozzle extension
Internal side - note left/right markings
The shell (without cable) measures approx 18 mm long, 18mm from top to bottom, and the main body is only around 10mm deep – with the nozzle extending a further 8-9mm. The body is L shaped, and the nozzle is perpendicular to the main body (rather than angled). There is one port on the external face which houses the LF tuning plug, and one port on the internal face with houses the ULF tuning plug. The nozzle has no lip, but is threaded, and the lip is provided by the addition of the tuning filter bores (which simply screw in place).
Nozzles upright - note the very smooth rounded surfaces
Main bore/filter fitting - screw in
ULF filter placement
Each IEM internal face has a L or R indicator stamped into the body mould adjacent to the cable connection socket. This socket is two pin, and takes 0.75mm pins – I.E. the same configuration as the UE TF10. The sockets are raised, with the cable plugs fitting snugly over the top for added strength. The cables also have L or R printed on the outer plug housing.
LF filter placement
MF/LF filters create natural lip for tips
Cable guides and TF10 type connector
Each cable has 75mm of formable memory wire for form fitting over your ears, and I find this quite handy for getting them to sit correctly when worn. The cable is 4 core single twisted copper strands in continuous twist from the plugs to the jack (the twisted pair becomes a twisted quad below the Y-split) which allows a simple replacement of the jack to convert to balanced.. Unfortunately the cable, while quite flexible, is also both microphonic, and also retains a lot of memory making it quite unruly. It tends to retain any kinks and can be quite difficult to fully straighten. One of the photos below shows the FLC8S next to the MEE P1.  Both were nicely coiled when I gently placed them in the light box. Its sad such a great design has such a poor cable.
Another view of the cable connection
The unruly cable next to the MEE P1 (beautifully coiled)
The 4 strand cable - easy to balance
The Y-split is a simple piece of heat-shrink, which is quite effective, and has another piece of clear plastic tube above it for a cinch – but unfortunately this does not work well with the cable jack (it is too tight – and therefore too hard to effectively move). The jack is right angled, gold plated, and has both good strain relief, and also is smart-phone case friendly.
Y-split and cinch
Jack next to filters (so you can see how small they are)
All in all, the build quality is pretty good and seems nicely robust. I'm not overly fond of the cable, and if this was to become my daily use IEM, the first thing I would do is to replace it with something having less microphonic and unwanted memory tendencies. For the price, it is one of the weaker points in an otherwise very good build.
The ergonomic shape of the FLC8S combined with the light weight, and well rounded surfaces make this IEM one of the most comfortable I've ever worn. If you take the time to properly mould the memory wire, it sits perfectly on my ears, and is definitely flat with my outer ear (which allows me to lay easily on my side with the IEM's intact). About the only slight issue I've found with the FLC8S is that it has a tendency over time to slowly push the preferred foam tips I use out of my ears. They never push all the way out, and don't usually break the seal – but I do wonder if the nozzles were slightly angled maybe the issue would disappear. Something for Forrest to consider with subsequent releases perhaps.
Spinfits and Sony isolation tips both worked
as did Spiral Dots and Ostry tuning tips
My preferred foams which also worked with no filter/bore
If I was using any of the tuning bores, they all come with a slightly serrated metal edge which allows for easy grip when fitting or removing – and this acts as a lip for the nozzle. This means that practically any tip will fit, and this includes smaller bore tips like Spinfits or Sony Isolation tips. And this also applies to Ostry tuning tips and even wider bore Spiral Dots. My preferred foams also fit well, and the only downside was that if you are using a foam tip, and change filters often, the serrated edge can tend to pull the internal bore tube out of the foam tips. Because I had to make so many changes when I was measuring all the filters – I actually destroyed two pairs of generic foam tips.
The one thing that some may not know is that you can also use the FLC8S without any internal bore filter fitted. There is enough of the nozzle to accommodate a tip but using this method means there is no lip. Fortunately for me foam tips fit well, and this has become my preferred default configuration.
Isolation with the FLC8S will depend on the seal you achieve, insertion depth, and also the choice of filters. Being a ported design with a shallow fit, I'd describe the isolation as adequate or average – without being excellent (few hybrids are). With music playing, you're isolated pretty well. They would be good for most public transport but I personally wouldn't be using the FLC8S for long haul flights.
So the new FLC8S looks good, has a good build, and is extremely comfortable to wear. Let’s have a quick look at my initial impressions, then take a look at the filters in more depth, and then move onto sonic impressions.
So the FLC8S had just arrived, I was keen on seeing how the filters worked, so I grabbed the included tweezers and attempted to remove the first ULF filter. Crack – plastic filter snapped at the head and was basically ruined. Thankfully there was a spare red one. So first lesson learned – the included tweezers are unwieldy, and basically there as a decoration (for me anyway, they are simply too big and pretty much useless). Much easier to simply use your finger nails.
So I carefully put a white cloth down, and proceeded to remove the red ULF and inset a clear. Slightly missed the hole (they are tricky) – said filter ricochetted off the housing, and disappeared into our carpet. After 10 minutes searching I gave up (thankfully again Forrest had included spares), so from that point on I have been super careful both removing and fitting the filters plugs, and haven't lost or broken another one yet. But word to the wise – these are really tiny, not easy to grip in bigger fingers, and quite frustrating at times to fit. Forrest – if you had a system where you could have a fixed dial with 3 or 4 settings, and the dial stayed intact – that would be a far nicer system! But I still have to give it to Forrest and his team – the “tweakability” of the filter combinations is quite incredible – and that is what makes this IEM so unique. So lets look a little more in depth at the filter system
The FLC8S comes with 3 different options for controlling the sound – an ultra low frequency port (ULF), a low frequency port (LF), and the tuning bores which control mid-range and high frequencies (MF/HF). Forrest advertises 36 different combinations and you have 3 ULF plugs, 3 LF plugs, and 4 MF/HF bores – so using simple math that gives 3 x 3 x 4 = 36 combinations right. Well actually not quite. The LF can be used without a plug, and it has another subtle change to the mid-bass. Also the nozzle can be used without a bore at all (I'll show you in a minute why I prefer it that way) – and that has quite a change on the frequency response. You could also remove the ULF filter – but I'm not counting that as an options as it cripples the sound. So the reality of tuning now is 3 (LF) x 4 (LF) x 5 (MF/HF) = a massive 60 different tuning combos.
MF/HF filters
ULF filters
LF filters
The only problem is that trying to make sense of all those options can simply be too daunting. But thankfully Forrest includes some recommended options and combos on the instruction manual – see the images.
Explanation of filters from the manual
Forrest's recommendations (see graphs at bottom of review)
Channel matching is excellent
Looking at the filters themselves – this is how they stack up:
Red plug
Most sub-bass
Grey plug
Medium sub-bass
Clear plug
Least Sub-bass
No filter
Most mid-bass
Black plug
Medium/high mid-bass
Grey plug
Medium/low mid-bass
Clear plug
Least (flattest) mid-bass
Gold bore
Most MF and medium HF
Green bore
Most HF and medium MF
Black bore
Medium MF and medium HF
Blue bore
Least HF
No Bore
Moves MF and relatively high HF
But the easiest way I can show you what I’ve found is simply to show the comparative changes by graphing them. The graphs below are generated using the Vibro Veritas coupler and ARTA software. I must stress that they aren’t calibrated to IEC measurement standards, but the raw data I’m getting has been very consistent, and is actually not too far away from the raw data measured by other systems except for above 4-5 kHz where it shows significantly lower than measurements performed on a properly calibrated rig. So when reading the graphs, don’t take them as gospel – or at least remember that the area above 4-5 kHz will likely be significantly higher. It is my aim to get this system calibrated at some stage in the future.
The graphs are provided merely as a point of discussion, and should be used for comparative results only – they do not reflect the true calibrated frequency response(particularly above 4-5 kHz). For each setting I've used the most neutral filters for the other settings (grey LF, grey ULF, and black MF/HF) as controls and then shown the range of filter options for the single filter being tested.
ULF filter
Three options – clear, grey and red. They are all a straight plastic, very small and fiddly to fit, and you do need to handle them relatively carefully (easy to lose and can break). They control the sub-bass pretty well, and their overall curves are very dependent of the LF filter used in tandem. The red filter has the most rise, and this does add some slam. The grey extends pretty well before a slow roll-off around 40 Hz. The clear has the least, but can also be the most natural depending on which LF (mid-bass) filter you use.
LF filter
Although there are 3 actual filters, in reality there is 4 viable options – clear, grey, black and none. The actual filters themselves are small, rubbery, and the hardest to fit. Often I found the black and grey filters quite close to each other (the graph shows it too), but you an get more variation when combined with different ULF filters. Once again the clear has the least mid-bass, and TBH the only time I really liked this one was when combined with the red ULF (creates a very flat bass signature). Using no filter here gives the most mid-bass, and as you'll see later in the review, provides some surprising results when configured to my liking.
MF/HF filter/bores
Easiest to fit, and 4 physical options – with each filter being just under 10mm long, and screw directly into the nozzle, creating a natural lip to retain the tips. Personally for me (while they were pretty good), none were perfect. My issue (and this is purely my preference) is that each filter had a bump to a varying degree between 1-2 kHz, then a drop-off between 2-3 kHz. You'll notice many earphones are often flat between 800 Hz and about 1.5 kHz before rising as they head toward 2 kHz. The reason for that is that the mid-range is where we are most sensitive anyway, and while boosting between 1-2 kHz can create heightened clarity around the vocal area, some can find this a little fatiguing, and it can also narrow the perception of sound-stage – bringing the vocalist too close. The other issue with bumping the 1-2 kHz area, is that if it is not followed with a subsequent rise (or at least flat) section in the 2-3 kHz area, you can lose some presence or sweetness - especially with female vocalists. The one thing I do like about these filters though is the way they provide options in the lower treble. Your choice will often be dictated by how sensitive you are to brightness, with the green being the brightest and blue the smoothest. I personally find the filter with the best overall cohesion between upper and lower mids is the green filter. It has the least bump at 1-2 kHz and it is tempered by a secondary small rise in the 2-3 kHz range which helps with presence, but unfortunately it comes with a cost of heightened treble.
Fortunately there is another option which involves removing the MF/HF bore altogether. This removes the 1-2 kHz bump, and leaves you with a rise at 2-3 kHz, but unfortunately also a big rise at around 7-8 kHz (which is quite a peak).
Real Versatility
And here is where I can show you how truly versatile the FLC8S really is. My ideal signature is a relatively flat bass with a slight mid-bass hump, and either flat extension through to sub-bass or slight roll-off. For mid-range I'm OK with a slight recession between the mid-bass hump and (hopefully) a nice gentle rise in the presence area at 2-3 kHz. After that – the lower treble area often doesn't matter as much to me, as long as there is enough presence to hear good decay on cymbals, and hopefully not trigger my sibilance areas. It's not surprising that many other earphones also mimic this type of response. Well choosing the clear ULF with no LF filter, and then no MF/HF filter gives an almost perfect curve. The clear ULF (least impact) combined with no LF (most mid-bass) gives a really nice flat curve with a gentle (and very natural sounding) mid-bass. And this combo with the mid-range bump moved into the presence area gives almost perfect balance. And in reality starts almost sounding HD600 like. It's not perfect – but for me it is something I can listen to for hours on end – and that is the magic of Forrest's filter system. My only wish is that there were a few more options with the bump in the 2-3 kHz area. Anyway – I've graphed my preference against the red/black/gold that many have talked about as being one of their favourite signatures. And remember I said I would have liked more room in the filter holder? This is simply because I have 2 HF/LF filter bores and 2 LF filters which I'm not using, and are effectively “spares”.
The great things is that there is no right or wrong – you set the FLC8S up the way you like it.
With 11 ohms impedance and 117 dB sensitivity, you can run the FLC8S from any source – power is simply not an issue. The one thing you will need to take into account though is the 11 ohm impedance – which suggests an ideal damping ratio of around 1ohm or less on your source. With typical pop/rock songs on the iP5S I’m usually at a volume level of around 25-35%, on the X3ii around 30-40/120. I did try amping with the E17K and IMS Hybrid Valve amp, and while I noticed no obvious signs of improvement from a driving point of view, both amps were pretty good matches for tonality. The Hybrid Valve amp brought a slightly softer tonality to the lower treble peak ( a really nice combo actually), and with the E17K I could apply -2 or -4 treble, and just soften the same peak. The result was brilliant. So overall I'd recommend amplification if you simply want to adjust the tonality a little, or if you have issues with high impedance on your normal source's output. You won't need it for the power.
It doesn't need it – and that is what the filters are for. But as I outlined above, it can be useful for smoothing peaks if you need to.
The following is what I hear from the FLC8S. YMMV – and probably will – as my tastes are likely different to yours (read the preamble I gave earlier for a baseline). Most of the testing at this point (unless otherwise stated) was done with my FiiO X3ii + IMS Hybrid Valve amp as source.
Tracks used were across a variety of genres – and can be viewed in this list http://www.head-fi.org/a/brookos-test-tracks.
The filter set-up I used was clear, none, none as outlined above in the filter section. I actually thought a lot about skipping this section altogether – but thought it was still important to write my thoughts on what is for me the best filter combo.
Thoughts on General Signature
The sound signature with this filter combination is well balanced with a slight tendency toward brightness, incredibly clean and clear, and tilted slightly toward more presence for female vocals (male vocals are still very good but have slightly less presence). Mid bass sounds beautifully natural with enough thump to be pleasing, but without anything dominating. Sub-bass is there, but again balanced and does not dominate.
Overall Detail / Clarity
Tracks used: Gaucho, Sultans of Swing
  1. Very, very clean presence and presentation with perfect balance and real cohesion between bass, mid-range (vocals), and upper end detail (hi-hats/cymbals).
  2. Extremely good detail retrieval with every nuance shown but not etched (it still sounds very natural). Cymbals are incredible – especially the decay.
  3. Guitar has wonderful edge – crisp and clean
  4. Vocals in both tracks are nicely presented in contrast to the rest of the track, and blend naturally.
Sound-stage, Imaging, and Sibilance Test
Tracks used: Tundra, Dante’s Prayer, Let it Rain
  1. Very precise directional cues, just outside the periphery of my head space – so very good feeling of width and reasonable feeling of depth.
  2. Imaging is incredibly clean and clear and excellent separation of instruments without being clinical.
  3. Dante's Prayer was practically perfect with stunning contrast between the cello, piano, and Loreena's excellent vocals.
  4. Good immersion (applause section of Dante's Prayer) with impression that crowd is around you (you are sitting right in it). Probably a little more width than depth, but good none the less.
  5. Sibilance is present in “Let It Rain” - I know it exists in the recording. However it isn't overly emphasised, and for me is very tolerable.
Bass Quality and Quantity
Tracks used: Bleeding Muddy Water, Royals
  1. Very good mid-bass impact and great portrayal of the overall dark mood. Mark's vocals have wonderful presentation of timbre, and texture (“Muddy Waters”) and whist they may not be as deep as I have heard them before, I am really enjoying this particular presentation.
  2. Good speed and bass resolution – not too boomy, but there is slight decay present.
  3. No signs of bass bleed into the mid-range
  4. Surprisingly good sub-bass (even with this filter combo) for rumble (“Royals”) but not over-done (perfect balance actually).
  5. Ella's vocals are incredibly presented – with good separation from mid-bass impact.
Female Vocals
Tracks used : Aventine, Strong, For You, Human, The Bad In Each Other, Howl, Safer, Light as a Feather, Don’t Wake me Up, Ship To Wreck.
  1. Wonderful transition from lower-mids to upper-mids – this is one of the strengths of the FLC8S with this filter combo
  2. Very euphonic presentation with good air and a wonderful touch of sweetness to female vocals
  3. Brilliant contrast between vocals and lower pitch of instruments like cello
  4. No signs of stridency with Aventine and Strong
  5. Really good mid-bass impact with music with highly dynamic content (Feist, FaTM) – contrast between bass and vocals is excellent.
  6. Superb with slower female vocals and especially with artists like Gabriella Cilmi, Norah Jones and Sarah Jarosz.
  7. I could listen to this filter combo for hours with any of my female artists. It's not just good, it's practically perfect.
Male Vocals
Track used: Away From the Sun, Art for Art’s Sake, Broken Wings, Hotel California, Immortality (Seether), Keith Don’t Go, Elderly Woman Behind the Counter in a Small Town.
  1. Presentation of male vocals will depend on how you normally like them, but this tuning is really extremely good and I'm appreciating how well this particular tuning does both male and female vocals without thinning either one.
  2. Bass presence is impactful from the mid-bass, and this provides good contrast with lead guitar.
  3. Excellent portrayal of classic rock artists like 10CC and Jethro Tull. Mix of detail and tonality is very good.
  4. Brilliant with acoustic tracks – especially Eagle's Hotel California. Spatial cues are very good with this live track too
  5. Showed a little thinness with Seether's cover of Immortality, but it doesn't take long to get used to the tonality and is still very enjoyable.
  6. Love the balance with Pearl Jam – and the texture and tonality with Eddie's vocals is very good. Cymbal decay was magic in this track (there is a lot of it). Another band I could listen to for hours. So clean and clear, and I think this is what really makes all vocal tracks stand out.
Other Genre Specific Notes
  1. Not going to go through all of these – as this is just such a great all-rounder
  2. Particularly strong with Jazz and Blues
  3. Loved classical – airy, detailed, sombre when it needed to be, light and deft for stringed ensembles.
  4. Would possibly add a bit more sub-bass for some electronic, hip-hop, trance or dub (just a matter of dropping the red filter in)
  5. Indie could get a bit peaky – depending on the recording, but easy fix if used with the E17K, or simply dropping the 7-8 kHz peak down with EQ.
This section is practically impossible to write as you can change the outcome depending on the filters. So instead I thought I'd stick with my favoured filter combo, and show you why I like it (by comparing it with some other reasonably well-known IEMs).
All of these comparisons are very subjective – and influenced by my own preference, physiology and bias. Comparison was once again with the X3ii + IMS HVA. All IEMs were volume matched with a 1 kHz tone and using a proper SPL meter (I used a splitter and variable resistor so I could swap back and forth quickly). The reason I chose each of these for comparison was very simple – all of them have roughly similar to this particular filter combo.
FLC8S (~$340) vs DUNU Titan 5 ($140)
FLC8S next to DUNU Titan 5
Graphed comparative frequency response

While the Titan 5 is less than half the price, it was one I though of immediately because tonally these sound extremely familiar. On build quality, the T5 has the advantage with the full metal shell, and it has a much better cable than the FLC8S. Fit on both is good and I'd be hard pressed to find a winner on the comfort stakes. Sonically the two IEMs are incredibly similar with the T5 having a little more sub-bass slam, while the FLC8S might have a little more mid-bass impact. They both have an incredibly similar mid-range with the same excellence overall in vocal presentation. The T5 is a little less spacious, a little more vivid, and a little brighter in its overall presentation. If I was shopping for one sound only, I'd probably pick the T5 – but the beauty of the FLC8S is that this is just one of the signatures it can mimic. If you are a tweaker – the extra outlay is worth it.
FLC8S (~$340) vs Fidue A83 ($270)
FLC8S next to Fidue A83 ​
Graphed comparative frequency response​
This time we're triple hybrid vs triple hybrid, and I think a few might be a little surprised with the similarity here between the FLC8S and Fidue's former flagship. Both have similar build quality and comfort. The FLC8S has the better cable connection system (Fidue had past issues with the MMCX connectors), but the Fidue has the better default cable (although I am now using one of Trinity Audio's). Sonically there are similar traits in the bass, transition to mid-range, and even the lower treble. The difference primarily is in overall speed (the FLC8S just seems to have quicker transitions), in mid-range weight (the A83 is slightly thicker but also more vivid), and in clarity and cleanliness of tone (the FLC8S is simply cleaner and clearer). Although the Fidue is quite a bit cheaper, this time it isn't a fair comparison. The added versatility of the FLC8S simply trumps the A83 – although both remain excellent choices.
FLC8S (~$340) vs DUNU DN-2000J ($300)
FLC8S next to DUNU DN-2000J​
Graphed comparative frequency response​
Again this is triple hybrid vs triple hybrid, and for this one I couldn't use the splitter because plugging both at the same time affected the bass response (both being very low impedance), so I had to plug and unplug. Build quality overall once again goes to the DUNU – the all metal build and quality of the cable is simply better than the plastic shell and unruly FLC8S cable (despite the 2000J cable not being removable). Comfort is with the FLC8S though with the better ergonomic fit. Sonically both are similar sounding from bass through to mid-range, with the main difference being in the upper mid-range transition through to lower treble. The 2000J has more heat in this area and this is something I haven't really noticed a lot in the past, but which is very apparent now that I'm used to the FLC8S. Switching between the two, I would call the 2000J slightly peakier and also the FLC8S a little cleaner sounding (and that is quite some achievement). Hard to pick a winner based on this filter combo, but again taking into account the versatility of the filter tuning it is really hard to go past the FLC8S – even compared to an IEM I absolutely love.


My time with the FLC8S has been a revelation – frustrating at times, but with plenty of “aha”moments along the way, and while I was somewhat less impressed at first, I've grown to slowly appreciate it more and more as time has gone by.
The overall build quality is very good despite its plastic shell, and the ergonomics really are top notch – very comfortable overall. The one issue (which many have commented on) is the cable. It is simply very unruly, retaining too much memory, and having slightly too much microphonic noise to be acceptable on an IEM in this price range. If there is one glaring thing Forrest should change first it would be the cable. Something well built and flexible like the Trinity cables or MEE P1 would be ideal IMO.
The real value of the FLC8S though is its filter system, and while they can be cumbersome to change, and confusing with so many options available, once you get used to them you can definitely tweak the sound a lot to match your preferences. My only gripe with the filters (aside from the fiddly nature) is that the tuning bores all have the same or similar 1-2 kHz bump which I personally find OK short-term but fatiguing long-term. In fact if I didn't have the ability to change this one particular trait, I would not be as positive towards this IEM as I am now.
The FLC8S won't be for everyone – you have to be prepared to experiment (a lot). It definitely helps to have a knowledge of the type of signature you like, and for me – my measurement system really helped me nail down the ideal combo.
So would I recommend this IEM – unreservedly so. While it is not perfect, the versatility you get for the asking price is well worth it. An easy 4 stars for me (with an extra 0.5 added for the innovation) – and all it would take would be inclusion of filters to move that mid-range a bit, as well as a decent cable, and this would be an easy 5 star review.
Well done Forrest – innovative, unique and truly well thought out. Thank you for giving me the chance to listen to and evaluate your creation.
The following graphs are my measurements of Forrest's default recommendations.  They show some of the versatility of the FLC8S:
Clear, clear, gold = vocal
Grey, black, gold = pop/rap
Clear, clear, green = piano or strings
Clear, clear, black = light music
Grey, grey, black = default
Red, grey, green = classical
Hello Brooko, thanks for the detailed review! I currently have the DN-1000s and GR07 BE and I would like to upgrade. I really like the DUNU’s bass and clarity and the GR07’s soundstage and balance. Ideally, I would like a (slightly v-shaped) IEM with articulate bass, not so prominent mids, brightish treble, wide soundstage and more “character” than the DN1000s. Would you recommend the FLC8s over the Pinnacle P1 or the 2000J? Cheers!
Hi Theo - you just pretty much described the P1. The mids on the FLC8S might be slightly too prominent for you - they are quite forward.


twister6 Reviews
Headphoneus Supremus
Pros: Resolving high def sound, pick from 36 filter combinations, premium replaceable cable, improved comfort w/custom fit design, unique storage case.
Cons: small filter pieces, not a common 2-pin cable connector (UE style).

This is a review of Custom IEM version of FLC8S 3-way hybrid IEM (will be referred in my review as FLC8C). The original FLC Technology FLC8S monitors are officially distributed by http://www.lendmeurears.com/flc-technology/, while the manufacturer website and FLC8C product page are still under development. I was told that expected price should be around 900-950 SGD, with faceplate options of carbon fiber (62 SGD), wood/metal/glitter/print (103 SGP), and steampunk (145 SGD). The review unit I received is a demo of a Custom FLC8 where the nozzle was modified to fit a regular eartip and the shell was modified for universal fit - set to me by LMUE in exchange for my honest opinion.
6/14 update: Official FLC8S Custom LMUE page is up: http://www.lendmeurears.com/flc8s-custom/ and the price was set at $674.  The page includes pictures of 19 custom housing colors and 14 custom faceplate options.

Often I’m being asked to recommend IEMs tuned for a specific sound signature or suited for a specific genre of music.  It’s not always the easy question to answer because the perception of a sound varies between people, and everybody has their own subjective opinion about it.  Even headphones tuned for a particular signature still have a degree of sound variation from the expected baseline.  And once we settle on a pair of headphones that we like, many still have a desire to continue with fine tuning by switching to different eartips which can change the amount of bass or switching to a premium cable which can add more sparkle to the sound.  Depending on a model, some IEMs even offer replaceable nozzle filters for a more noticeable sound adjustment, but nothing too drastic.
One headphone manufacturer decided to take the idea of sound tuning a step further, and actually leapfrogged to a whole new level with a patented filter system like nothing I have seen before.  Even so FLC Technologies was started by Forrest Wei not too long ago (in 2011), he has many years of experience working for Ultimate Ears, Jabra, MWM Acoustics, and Harman.  With all this experience under his belt and fueled by a passion for design and innovation, Forrest made a serious attempt to reinvent the wheel of IEM sound tuning by using multiple filters in his debut release of 3-way hybrid FLC8, later replaced by FLC8S with improved build quality and updated cable.  Now, with a support of Teo and his Lend Me UR Ears, they are taking it to yet another level with soon to be available Custom model which I had a chance to test and would like to share with you about.
Unboxing and Accessories.
While the original FLC8S featured a unique jewelry box packaging (similar to PAW Gold box), FLC8 Custom (FLC8C) stepped it up with VIP Aluminum mini-briefcase box with a stamped FLC Technology logo on the top cover.  Actually, it comes in a cardboard box with a see-through film window on the top, but once you lift that top open you will see a legitimate high quality aluminum mini-briefcase with a latch.  The only thing missing was a handle which would have been cool.
With a storage briefcase open, you will find removable egg crate foam lining in the top cover and a layer of foam lining with cutout partitioning on the bottom.  When it comes to the included accessories, the owners of the original FLC8S won’t find any surprises.  You get their familiar metal round storage container which has a top part with a thread to keep it securely closed, and unfortunately still lacking a lining to protect its content from banging inside during the transport.
You also get 1/4" adapter and an airplane plug.  I consider both to be fillers – but hey, maybe some will find it useful.  A basic cleaning tool was included (actually there was two), one to clean bores of the nozzle and the other one probably to help with removal of nozzle filter.  I also received a set of eartips because my review pair of FLC8C was designed with universal nozzle to fit eartips.
The package wouldn’t be complete without plastic fine point tweezers to assist in handling of small filter parts, and the blue bullet keychain designed to store various filter pieces fitted inside of its rubber holder.  Very generously, Lend Me UR Ears also included a 2nd set of filters in a small plastic bag – it’s easy to lose them during removal/install, thus an extra set was very welcome, and it could be purchased separately as well.  The included manual was in Chinese, but I was able to correlate filter designation by comparing to FLC8S English manual.  ULF and LF filters are the same, and instead of a removable nozzle (MF/HF) filters, now you have double plug with a few different colors I had to guess.  When FLC8C is ready for international shipment, a translated English manual will be included.
flc_flc8C-01_zpsliyme2al.jpg flc_flc8C-02_zpscq95bwti.jpg
flc_flc8C-03_zpspx0sgcn3.jpg flc_flc8C-04_zpsltmpktni.jpg
flc_flc8C-05_zpsw9fekfcj.jpg flc_flc8C-06_zps5s7m6int.jpg
flc_flc8C-07_zpsnjhvi7ru.jpg flc_flc8C-08_zpsazqooxrq.jpg
flc_flc8C-09_zpsbmdxwsbh.jpg flc_flc8C-10_zpspnr7frpj.jpg
I haven’t seen the cable from the original FLC8, but the fact it was updated in FLC8S tells me it had some issues.  Also during my brief testing of FLC8S, I wasn’t too crazy about its OFC cable either due to a rather springy wire and some microphonics.  Another annoying part of it, it uses a 2pin connector which is not universal but rather 0.75mm type found in legendary UE TF10 (hint, hint – Forrest connection to UE).  It’s definitely not the end of the world since you can still find replacement aftermarket cables with this connector, and any custom cable maker can utilize it as well.  But I wasn’t able to take advantage of my collection of aftermarket universal 2pin cables because they don’t accommodate 0.75mm spec.  As a matter of fact, you have to be very careful not to jam other cables by mistake.  Also, even so I had no issues with it, the connection of this UE-style socket is not as tight and secure as a common universal 2pin connector.
But there is a “silver” lining to this cable situation – FLC8C comes with a single crystal silver upgrade cable, an included $107 bonus which can be purchased separately as FLC8S accessory from Lend Me UR Ears.  I actually like this cable a lot better over the original one included with FLC8S.  It still has some memory effect, but not as springy, has a heat shrink tube for y-splitter, another sliding tube piece which functions as a chin slider, and a pre-shaped springy sleeve for over ear fit without annoying memory wires.  2pin connectors were angled and had red/black ID dots, and on the other side of the cable you have a right angled 3.5mm TRS headphone plug with a decent strain relief.  All 4 wires go to the connector, so would have been great to terminate it with a straight 2.5mm TRRS balanced plug and add 3.5mm TRS angled adapter – maybe something for FLC and Lend Me UR Ears to consider in a future.
Now, the million dollar question:  is there a sound benefit when using “single crystal” silver cable over the stock OFC cable?  Being quite familiar with effects of different wire material which I have tested across many IEMs/CIEMs and various cables from my review collection, I had some expectations when switching between FLC8S stock and FLC8C upgrade cables, but arrived to a different conclusion.  While testing with all gray filters, what I consider to be a baseline sound sig, surprisingly I found this silver wire cable to improve low end resolution and articulation without affecting too much mids or highs.  It improves sub-bass texture and slightly elevates its quantity which in a relatively comparison was a bit rolled off with a stock OFC cable.  This is not a typical sound change I hear with my other thicker wire pure silver cables that usually brighten the sound of other IEMs I tested, but regardless of that – I liked the effect of this cable on FLC8C.
Even without a sound improvement, I still like the new cable design and consider it to be a step up from the original FLC8S cable.  The improvement in bass performance, as I hear it, is just a bonus.  But I was still left wanting to try it with other silver or silver plated cables to hear the difference.  I hope down the road FLC will consider switching to a more common 0.78mm 2pin connector design, or at least offer it as an option when choosing Custom configuration of this IEM.
flc_flc8C-11_zpsebopmot5.jpg flc_flc8C-12_zpspwehvkoz.jpg
flc_flc8C-13_zpszo55fbp7.jpg flc_flc8C-14_zpsgherxd3d.jpg
I’m still amazed how FLC was able to fit a dynamic driver and a pair of BA drivers all inside of their original slim lightweight FLC8S shell.  Though I have seen the diagram of the 8S design, I would have loved a glimpse inside through a transparent shell to see it "in person".  Also, I was a bit on the fence about the fit due to combination of a small shell with a springy cable.  This is purely a subjective opinion and probably has to do with my ear anatomy, but on a few occasions the earpiece popped out of my ear, and a thought cross my mind wishing for the shell to be bigger.  Custom version of FLC8 turned out to be the answer to this prayer!  Actually intended for audio trade shows, FLC and Lend Me UR Ears made a few samples where the shell was modified to have a universal shape to fit any ear and the nozzle was replaced with a universal 2-bore design which accepts common eartips.
Obviously, the official Custom version will be designed from your ear impression mold which you need to get from your local audiologist, and the final shell design should fit your ear like a glove.  But even with Universal version of this Custom FLC8C, I was able to get an excellent fit with a great isolation.  Once it becomes available, you will be able to customize it, including different faceplate designs such as carbon fiber, wood, metal, glitter, custom print, and even steampunk.  My review unit arrived in a semi-transparent yellow color shell, and I was grateful for being able to take a glimpse inside to see the arrangement of the drivers, and how the sound tubes and filters interact with each other.  As a result of these Universal-Custom modifications, my review unit ended up looking a bit Frankenstein-ish, but I'm sure the official Custom shell will have a more premium look.
The biggest selling point of this design, at least for me personally, was the larger size shells and a better quality cable which yielded a perfect fit and improved comfort to the point where I forgot I even had them in my ears.  Just don't expect to fall asleep with your head down on the pillow while wearing FLC8C since they are not exactly flush and do stick out a bit.
flc_flc8C-16_zpsbgjmaq7n.jpg flc_flc8C-17_zps2jek3xpk.jpg
flc_flc8C-18_zpscvfadwi0.jpg flc_flc8C-19_zpsow6zheml.jpg
flc_flc8C-20_zpsg1cyxccf.jpg flc_flc8C-21_zpsqvqbdvjq.jpg
The fit.
Sound Filters.
I'm sure many associate IEM filters with some sort of a replaceable nozzle filter and a predictable selection of three pieces with a default sound, reduced bass sound, and enhanced bass sound.  FLC decided to approach the filtering method in a completely different way.  They split their filters into 3 groups: ULF (ultra low frequency, associated with sub-bass), LF (low frequency, associated with mid-bass), and MF/HF (mid and high frequencies associated with midrange and treble).  Keep in mind, this is a hybrid design, thus ULF and LF will be focused on fine tuning the sound of Dynamic Driver, and MF/HF will be focused on fine tuning the sound of Dual BA drivers.
This filtering system is nearly the same as found in FLC8S, with the only exception of a nozzle filter.  With 8S being a more traditional universal design, you unscrew and replace the nozzle part which controls a combined bore opening.  Custom FLC8C has a 2-bore nozzle design with a dual rubber-plug filter to control MF/HF.  Having the advantage of a clear shell, I can trace the path from a Dual BA going to one of the bores where the corresponding side of the dual plug has an actual filter while the Dynamic Driver (DD) goes to another bore and that side of a dual plug filter only varies in the opening width.
The actual filtering of DD is done through 2 vents in the shell using the corresponding ULF and LF filter plugs.  The low frequency (LF) replaceable rubber plug goes into the vent located right across the DD.  The sub-bass frequency replaceable plastic push pin (ULF) goes into the separate vent with a tube connected to the output of DD driver.
Each earpiece has 3 filters, one going into the nozzle and the other two going into the faceplate of the shell.  Each filter is color coded and corresponds to the following:
ULF: clear - less ULF, gray - medium ULF, red - most ULF
LF: clear - less LF, gray - medium LF, black - most LF
MF/HF: clear - lower HF, gray - medium MF and medium HF, gold - most MF and medium HF, green - medium MF and most HF.
If you do the math, you'll end up with 36 different sound combinations!!!  I'm not aware of any other IEM that can pull off the same.
Sound Analysis.
With so many unique sound combinations, how would you even describe the sound?  Based on filter description where gray is considered to be a happy "medium", I started with that setting as a baseline sound of FLC8C.  With all 3 filters selected as gray, I hear a very resolving, reference quality, expanded sound with a balanced signature, excellent retrieval of details, and an impressive transparency.  FLC8C has an excellent extension of the low end and high end (deep low end extension down to sub-bass, very textured, very articulate), punchy mid-bass, nicely balanced mids with just a perfect amount of body and excellent retrieval of details, sometime even down to a micro-detail level, and a high definition crisp airy treble.
Soundstage is definitely above the average, though I do hear a bit more width then depth.  Layering and separation of instruments and vocals is very good, with a decent imaging that has a very convincing placement of instruments and vocals which actually improves as you switch to brighter high frequency filters.
Now, starting with this all-gray baseline, I will go into a brief description of each filter variation and its effect on the sound.
*** MF/HF variation
gray - gray - clear: treble and upper mids are a little rolled off, while low end and lower mids stay the same, sound becomes a little smoother and warmer.
gray - gray - gold: lower mids become a little bit thicker but not muddy, and as a result of this I hear treble a bit rolled off.
gray - gray - green: treble gets boosted and becomes a bit grainy, but you do hear an improvement in airiness.
*** LF variation
gray - clear - gray: noticeable reduction in mid-bass where it becomes more neutral and flat.  It also thins out lower mids a bit, making sound more reference quality.
gray - black - gray: adds more mid-bass hump, the same speed, just a little bit of quantity boost, but I do hear more body in lower mids which now sound a lot thicker, making overall sound a bit less transparent.
*** ULF variation
clear - gray - gray: i do hear sub-bass slightly more rolled off, but it's a rather subtle change, sub-bass is still extended but has a little less quantity.
red - gray - gray: beefs up sub-bass without too much exaggeration which also improves the impact of the mid-bass. While LF boost affects lower mids, ULF boost affects/improves the whole sub-/mid-bass in a very positive and controlled way.
*** favorite combo ***
red - gray - gold: my favorite low end setting with a very articulate and well controlled bass and a smooth yet still detailed top end.
red - gray - gray: the same as above, but with a more revealing and airy top end.
flc_flc8C-28_zpsc488up6v.jpg flc_flc8C-23_zps3oscfray.jpg
flc_flc8C-24_zpsikffyzso.jpg flc_flc8C-25_zpsb5p2ewlh.jpg
flc_flc8C-26_zpsua1z20zv.jpg flc_flc8C-27_zpswk2mmg9w.jpg
Comparison to other headphones.
This comparison was done using PAW Gold as a source, and FLC8C in its default filter config (except for 8S vs 8C comparison).
FLC8S vs FLC8C – even so we are dealing with the same 3-way hybrid design and nearly the same filtering system, the shell design and the nozzle filter difference should account for some changes.  I used my favorite red-gray-gold filter setting on both for a comparison.  The first difference I hear is 8C soundstage being a little wider, while 8S has a little more depth.  The bass and the treble between these two sounds nearly identical, but I hear the difference in mids where 8C has more energy and a little better retrieval of details while 8S mids sound a little dryer and more withdrawn.
FLC8C vs DN2kJ - DN has a similar soundstage expansion, not as deep sub-bass extension, more neutral bass in comparison, leaner lower mids, brighter upper mids, detail retrieval is similar (though DN is more analytical), DN has slightly better treble extension with more airiness.  Overall FLC8C is smoother with fuller body vs DN2kJ being leaner and more vivid.
FLC8C vs Primacy - similar resolution but Primacy by default has a more lifted low end with a heftier sub-bass and a stronger mid-bass, a little more body in lower mids, similar upper mids, and more rolled off treble.  Very similar soundstage, though FLC is a little bit wider.
FLC8C vs A83 - FLC soundstage is a little wider.  Mids and treble are very similar but the big difference is that A83 has more impact in the low end with deeper sub-bass and more mid-bass punch.  In this comparison FLC is more balanced and has a little better resolution.
Regardless of Universal or Custom design, FLC8x is one very impressive pair of 3-way hybrid IEMs with an excellent resolution, great sound extension and soundstage expansion, and a very flexible sound tuning.  Its triple-filter sound customization is what sets it apart from any other tunable monitor I have ever tested.  You almost feel like a sound designer, going through different filter combinations, adjusting the sub-bass, mid-bass, mids, and treble to tailor it to your exact liking.  It's true that filtering pieces are very small to handle, but typically you shouldn't be going back'n'forth with constant adjustments, though it's tempting.
The biggest question in here is if Custom FLC8C worth nearly the double price of Universal FLC8S?  The word "double" has quite a weight to it, until you stop and think about the actual price of the universal version and realize that if you take into account a premium cable and a premium aluminum storage case, you are only paying about extra $200 for an improved Custom shell design with a superior fit and isolation.  I have a feeling many diehard fans of FLC8S will probably justify this price difference to turn this one of a kind 3-way hybrid IEM into one of a kind Custom fit earpiece.  And for those who have been eyeballing FLC8x design, the FLC8S still has one great value.
@Wyd4 : keep in mind, my review CIEM unit was a demo modified to be universal so I can use with eartips.  For the Custom version of FLC8S you need to send your ear impression and you will have a custom made shell with all the corresponding "commitments" :wink:  Maybe you can ask them to make a special order with universal custom shell.  If enough people request, I'm sure it will get FLC/LMUE attention to add it to their customization list.
Oh apologies. For me the biggest worry with ciem is the what if the sound isnt quite for me. This monitor eliminates that to a degree.
Thanks for review. Which one is a better choice?
Dunu 2002 or FLC8s?


Headphoneus Supremus
Pros: Adjustable sound signatures, great packaging,
Cons: Caused some fit issues, cable lacks appeal, filters easy to lose
FLC Technology were a company I'd never heard of until they surfaced on Head-fi late last year. They’re a Chinese based company with some very interesting ideas in regards to customizing your portable audio experience. Hybrid in-ear monitors have always been popular among the Head-fi crowd, with the use of a dynamic driver and balanced armature used in unity you can produce some excellent performance, it seems everyone including Sony are giving it a go. Where FLC Technology push the game further is adding a complete filter adjustable hybrid so you can cater the sound to 36 different approaches! 
  1. Sensitivity 107 dB/mW  @ 1000Hz
  2. Frequency Response 20Hz - 20Hz
  3. Drivers x1 8.6mm Dynamic + x2 Balanced Armature
  4. Impedance 11ohm
  5. Cable length 1.2m (detachable UE two pin configuration)
  1. $349 USD (found at lendmeurears.com and other selected vendors)
Much thought went into the packaging the entire presentation arrives in a heavily built cardboard box with inserts that flick outwards and a design speech in itself, its not the kind of thing you would throw away after removing the earphones. Its built to last as a storage container for your accessories, filters and looks great in person. It is quite heavy though so one must take this into consideration.
When I first laid eyes on FLC8 I would have believed the housings are actually metal or some form of durable aluminum, after some investigating it appears the housings are made of plastic, but like I said you'd never know unless you were told. This goes for the appearance and the feel of the housing. You can get them in two different colours (blue or red) and personally I think both look great with a little bias towards the red in colour.
The cables are detectable as are the front filters which all appear to have decent threading and connections. There is however a short guide to take care when removing the cables as they're not 100% fool proof and can be damaged if care is not taken. I'll also add one should only remove the cables when absolutely required. While they're indeed detachable they're not 'indestructible'.
I will say the cable is a little under the weather, it looks nice in photos but is a little stiff and doesn't feel all that premium to the touch, it has that wirey feeling that retains spring and may seem a little springy for those on the go in the outside world. The beauty of FLC8 is however it can use any third party UE two pin cable for those who want to upgrade, sound, aesthetics alike.
Fit / Isolation:
Unfortunately for me getting a fit with FLC8 was a little underwhelming, particularly the left side liked to pop out of my ear often, I was able to keep them secure by lifting my ear before inserting the tip however over time it would wiggle its way out and I found myself pushing the left earpiece back in. It was ok sitting down or lying in bed but on the go they gave me some issues no matter which way I adjusted the ear guide or tips used. I think maybe because the housing is unable to pivot.
I will say the majority of owners (and there are many) have not had the same issues so it appears the fit issue would be isolated to a selected few who just don't fit the mold correctly. I had read one other thread on Head-fi where a member had the same issue. Isolation was also affected because of the fit issue but I'll say once sealed isolation was more than satisfactory but not an entirely strong point for my experience, especially outdoors.
Included in the package is:
  1. x12 Silicon tips ( Small / Medium / Large)
  1. x1 Round metal case (very strong / durable)
  2. x9 Low frequency tuning plugs
  3. x9 Ultra Low frequency tuning plugs
  4. x8 Tuning nozzles
  5. x1 Pair of tweezers (for using installing the filters)
  6. x1 Filter storage case
  7. Airline adapter
  8. 6.3 to 3.5mm Jack Adapter
  9. Tuning guide
  10. Ear wax cleaning tool
Filter System:
The most inspiring part of FLC8 is the tunable filter system allowing up to 36 different sound signatures. By changing the nozzle and two small filters located on the housing you're able to alter the sound signature closer to something you prefer. You can adjust the ultra low frequency, low frequency and mid-range which is a separate filter that attaches to the housing nozzle.
I will show some illustrated pictures from the supplied tuning guide:
Because there are so many customization's available one would be mad to go through each one and write about them (absolutely mad I tell you). So what I have done is adjust FLC8 to what I feel is inline with my preferences which are bright/analytical. By doing this I'm able to mold FLC8 into something close as possible to my desired sound signature and write a sound description.
The configuration I went for is:
  1. Red: Ultra Low Frequency
  2. Grey: Low Frequency
  3. Green: Mid-range Frequency
Files used:
  1. FLAC 16/44 (all files)
Sources used:

  1. iBasso DX80
  2. Cayin N5
  3. iBasso DX90
With the red filters installed one of the best tracks to test sub-bass is Michel Jonasz – Le Temps Passe. Extension is good, the texture is great and there's a nice presence of clarity in the low-end. I won't say its the the most extended I've heard but most certainly a nice low -end. It has the correct speed and punch but still to my ears doesn't push out the most quantity. But even then its more than present and shows enough quality bass for its price range to impress the masses.
With the green filters attached to the nozzles I was able to make FLC8 sound quite vibrant and on the brighter side, it makes a good experience for those who like a nice amount of clarity and detail in their presentation. I would even lean to say if your seal isn't correctly done you may even find them a little too lean. Detail levels are well present however I do wonder if something like Fidue A83 can push out a little more for the price between them.
Refinement is nice, there's a nice tonality which again shimmers through the mid-range giving a quality timbre, areas like the upper mid-range have a nice push at times with vocals. All in all the quality of FLC8 is quite nice and I understand why people rave about them. There's hardly any siblance to be found and the earphone presents itself well.
For testing treble and an IEMs ability to remain stable its always good to throw some modern recorded EDM tracks or electronic music, its these tracks that will test an the IEMs extension, refinement and strength at not showing any peaks or sibilance in the highs. FLC8 pulled this off nicely, even with the brighter green mid-range filters installed. It doesn't have the end to all in extension but does a clean job and showing itself.
If I had to fault the treble it could sound a little metallic or one noted at times, Kind of ticking away in the background and allowing the mid-range to come through over the top. But again, I must stress this is just with my filter set up!
Strong point, not the end to all but for the price a skilled area of this earphone, you get a good sense of instruments separating and even ticking in time together with the correct tracks. I would even say the amount of separation is slightly stronger then my main reference IEM in this price range, Fidue A83. I was impressed with this area.
There is decent width but not a completely strong point, you won't feel anyway closed into the presentation and from my experience the sources used will completely alter this. I don't however perceive much depth from FLC8 it does sound a little flat in the center channel but most certainly not something that's going to draw your attention or distract you.
Remembering I've only gone through one option of filters I really can't fault the sound I heard, it was on the brighter sound for those who like lean tonality and It does perform well. The accessories and build are nice, the entire idea of bringing such a customized earphone to the market in itself a great thought. The only real problems I can mention are the fit issues I experienced and the possibility of losing the filters, they're so small and fiddly to set up. I think while adjusting is fun many will find the correct set up for their personal preference and stick with it.
I see lots of potential in the concept and its obvious appealing to the masses as the Head-fi thread for this earphone is well populated and healthy. Many members are completely happy with the performance and then some more. For me FLC8 won't become my every day earphone because I have those fit issues and personally I still lean a little towards Fidue A83 in this price range. At the end of the day, FLC Technology produced something different, unique, a one off of their own, and that's the beauty of FLC8.
I'd like to thank FLC Technolgy and @DJScope for arranging the tour!
H2O how is the imaging of the flc compared to a83?
@Skullophile I'd say they're very close as I didn't notice one pull away heavily in imaging. @Signal2Noise This was a tour unit, I've placed it in the only FLC8 review section on Head-fi, sorry for any mic up. Hope you enjoy yours soon! @woye263s personally I still prefer Fidue A83 over FLC8 and I'm yet to find another in the mid-tier IEMs that performs quite as well. DN-2000J or the newer model might also be worth considering
Thanks, which one would you buy? DUNU 2002 or FLC8s?


Headphoneus Supremus
Pros: that sweet & detailed midrange!, instrument separation, versatility, build quality, bass speed, coherency, good resolution
Cons: tweezers useless even when correctly operated (better use your fingernails), upper treble refinement could be slightly better, microphonic stock cable


There are various universal in-ears out there that feature replaceable sound tuning filters that guarantee for a (sometimes more, sometimes less significant) sound alteration to one’s personal preference, but there hasn’t been any that allows for 36 filter combinations – well, at least until now, as the FLC Technology FLC8s does indeed offer three filter groups that can be combined to 36 possible filter combinations.
FLC Technology (flctechnology.com) is a Chinese audio company that was founded in 2011 by Forrest Wei. The letters F, L and C (pronounced “Fu Lai Si”) by the way stand for “Happiness/Fortune comes here”. Before FLC, Forrest has worked as engineer at various renowned audio companies for many years (his vita contains Ultimate Ears, Jabra, MWM Acoustics and Harman), and this experience can be indeed heard with his latest creation, the FLC8s. Before this model, FLC Technology offered a custom-moulded hybrid in-ear that offered the same patented filter technology.
What’s quite special about the FLC8s is that unlike many other hybrid in-ears which feature a coaxial driver design layout where the midrange/high frequency drivers sit in front of the dynamic woofer and end in a large single-bore nozzle, Forrest’s creation features an independent dual-bore design that merges before the nozzle, which allows for the individual tuning of the different driver designs.

A sample of the FLC8s In-Ears was provided to me free of charge for the purpose of an honest evaluation. My hearty thanks go to FLC Technology’s Forrest Wei and Lend Me UR Ears for this opportunity.

Technical Specifications:

Price: ~ $349 (http://www.lendmeurears.com/flc8s-red/)
Sensitivity: 107 dB/mW @ 1000 Hz
Frequency Response: 20 Hz – 20 kHz
Drivers: 1x 8.6 mm dynamic, 2x Balanced Armature
Impedance: 11 Ohms
Cable Length: 1.2 m

About Hybrid In-Ears:

As you can read from the technical specifications, the FLC8s is a little different from most In-Ears and doesn’t only use dynamic or Balanced Armature transducers, but combines both in one shell.

Most In-Ears use dynamic transducers for audio playback which have the advantage of covering the whole audible spectrum and achieving a strong bass emphasis without much effort. Valuable dynamic drivers are often said to have a more bodied and musical bass that has a more soft impact and decay and lacks of the analytical character that BA transducers are known for. On the downside, in contrast to headphones with other driver principles, dynamic transducers often have a lower resolution.

Higher-priced and professional IEMs mostly use Balanced Armature transducers, which usually have got a higher resolution than dynamic drivers, are faster, more precise and have got the better high-level stability, which is important for stage musicians that often require higher than average listening levels. On the downside, it is quite hard to cover the whole audible spectrum with just a single BA transducer and strongly emphasised bass is only possible with multiple or big drivers. Some people also find In-Ears with BA transducers to sound too analytical, clinical or cold (in several active years in a German audio community where I wrote multiple reviews, gave dozens of purchase advice and help, from time to time I heard people that got into BA earphones for the first time using these attributes for describing BA earphones, especially their lower frequencies).

Hybrid IEMs unite the positive aspects of both driver principles and use one dynamic transducer for lows reproduction and at least one BA driver for covering mids and highs, wherefore the often as “musical” described bass character remains and the BA transducers add resolution and precision to the mids and highs – and that’s what the FLC8s does with its technology. It is addressed to those people who perceive the clinically-fast character of BA transducers as unnatural, but want to keep the mids’ and highs’ resolution, speed and precision.

Delivery Content:

For me, a valuable product deserves an appropriate packaging, and the FLC definitely does not disappoint in this regard.
On the outside, the slightly larger, surprisingly heavy and sturdy box is rather plain looking with its pale sand colour and the silver logos, but offers a quite interesting and well-thought, unique way to open it, whereon the arrow with the “open here” text in the lower left corner already gives a hint. The front (and all ensuing sides that can be opened) is magnetically attached and can be folded up, kind of like a chest. Then, the in-ears which are embedded in blue foam become visible. Pushing on the foam where the black arrow with the “press to open” text is located, it can be taken out; inside this upper layer are large plastic tweezers and a quick-start guide that explains the filters and gives some combination examples.
On the front, another arrow with “open here” text points to the left side which can be swung open as well, then the whole top layer with the foam can be flipped away to the right side, which is pretty cool in my opinion. Inside the second layer, one can see the blue foam again which embeds the carrying case for the in-ears as well as the small cylinder that contains the filters.
In a plastic bag are a 6.35 to 3.5 mm adapter, a cleaning tool, an airplane adapter, four pairs of black silicone tips, three pairs of white silicone tips (the fourth pair of the white tips is already installed) as well as finally six spare tuning filters for the bass and sub-bass.

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Looks, Feels, Build Quality:

The in-ears are available in two colours (red or blue), quite small and made of plastic, which I wouldn’t have noticed if I hadn’t randomly read it somewhere on the internet, as I really thought FLC8s’ bodies were made of metal, as they feel very sturdy, are extremely well varnished (wherefore they appear like they were made of metal) and the used plastic is of very high quality; additionally no glue residues can be found at the part where both body halves are joint.
On the inside are the holes for the sub-bass filters; also on the inside are the side-markers on the bodies as well as on the cable connectors. On the outside, the holes for the bass filters can be found. The filters for the midrange and treble are made of metal and screwed into the nozzle.
Except for the mids/highs filters, the other rubber/plastic filters for the lows are really small and easy to loose, wherefore changing them should be best done with steady hands and when sitting.

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The cable is of dark blue colour, replaceable and features the same 2-pin connector system as the Ultimate Ears Triple.Fi 10 (0.75 mm pins). Although it has got the typical, valuable, twisted quad-litz style from the professional audio sector, it is a bit springy (though at the same time quite flexible, nonetheless not as flexible as other twisted cables) and has a cable cinch (chin slider) that sits enormously tight so that it can only be moved with much effort. To top it all, it is quite microphonic, but more about that in the next “Comfort, Isolation” paragraph.

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The carrying case is made of metal and I quite like it: although it may not be best suitable for fully portable use, it looks and feels very valuable, massive and has got precisely cut threads. The outside has a really beautiful gunmetal-blue finish and is completely bolstered with fabric on the inside (which is in my opinion a must for every in-ear case – I can’t stand bare plastic or metal on the inside of a protection case), so the in-ears are well protected.
The small blue cylinder with the keychain for the tuning filters strongly reminds me of the one that came with my Shure SE846, however the blue one of the FLC8s has got the benefit that the filter elements are stuck into a block of rubber, so it is less easy to lose the seven pairs which are inside (the three others are in the in-ears themselves).

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Comfort, Isolation:

The in-ears are actually quite small and are easy to insert into the ears; then they sit very securely and comfortably, whereto the cable connector’s angle also plays a leading role. With my large ears, I have almost never problems with the fit of in-ears anyway, so these sit extremely well in my ears, too – but even most people with (very) small ears should be able to get a really good fit and comfort with the FLC8s.
Like most models in this price range, the in-ears are supposed to be worn with the cables over the ears which usually improves fit as well as comfort and drastically reduces microphonics – unfortunately the latter is not true in this case, as FLC8s’ cable is quite microphonic for a model of its kind and transports cable noise with every small touch or movement – pity! Tightening the cable cinch behind the head and then guiding the cable over the shoulder, microphonics are slightly reduced, however still obviously stronger than they are supposed to be.

Isolation is better than average, however not as strong as with fully closed in-ears. Nonetheless, exterior noise is blocked out somewhat more than with many vented in-ears.


For testing, the source devices I used were the iBasso DX90, Leckerton UHA-6S.MKII, FiiO X3 (first generation) as well as LH Labs Geek Out IEM 100. Music material was mainly stored in FLAC format (lossless rips of my CDs in 16 Bit/44.1 kHz), but I also used Hi-Res, DSD and some MP3 files.
I used the largest included white silicone tips for listening.


The major question I had to deal with while testing was “how do I best describe an in-ear that allows for up to 36 different sound signatures by using different filter configurations?”.
My decision was then to first describe all filters and their effect individually and then finally to give a couple of different sound descriptions of a few filter combinations.

Overall there are 10 pairs of filters that can be summarised in three groups that alter other frequency ranges, wherefore up to 36 different sound characteristics are possible (3 x 3 x 4 = 36). Included are three pairs for the sub-bass (“ULF”) that are inserted on the inner side of the bodies, three pairs for the bass (“LF”) that are inserted on the outside as well as four pairs that are screwed into the nozzle and have an effect on the midrange and treble (“MF/HF”).

The different filters listed in tabular form:
Clear = Minimum
Clear = Minimum
Blue = Minimum HF
Grey = Medium
Grey = Medium
Gunmetal = Medium MF & HF
Red = Maximum
Black = Maximum
Green = Medium MF & Maximum HF
Gold = Maximum MF & Medium HF

Ensuing are a few frequency response measurements of the different filters and the effect that they have on the frequency response. The plots’ colours also represent the filters’ colours.
Please note that the plots weren’t recorded with professional equipment but with my Vibro Veritas coupler that was pseudo-calibrated to more or less match a real IEC 711 coupler’s response with applied diffuse-field target, hence the results shouldn’t be regarded as absolute values but rather as a rough comparison and for getting a general idea of the sound. Especially at 3, 6 and 9 kHz, there are sometimes greater deviations from professional plots, but for a general, rough comparison between various in-ears and filters, the results are sufficient.

(ULF Filter  I  Grey  I  Gold)


(Grey  I  LF Filter  I  Gold)


(Grey  I  Grey  I  MF/HF Filter)


With these in-ears, the focus lays obviously on the ability of individual sound adjustment with the help of the included filters that can form up to 36 (3 x 3 x 4) different combinations and sound signatures. For changing the filters, large plastic tweezers come included. For daily use, I found using my short fingernails (less than 0.5 mm) to be more helpful for changing the filters, as that gave me better control over the filigree things and they also slipped out of my hands way less often, nonetheless it is quite a fiddling to get them in and out. Probably smaller, rubberised tweezers would be more practical.

What follows now is a small selection of different filter combinations that are displayed in this form: [ULF]/[LF]/[MF/HF]
01: Grey/Grey/Gold:
This is the filter combination the in-ears arrived with.
The sound signature of it goes like this: down from 500 Hz, the bass emphasis which raises very evenly and flat begins and forms its climax which is about 6 dB north of neutral sound (Etymotic ER-4S) below 100 Hz, in the midbass; sub- and midbass are even plus plane and also in the sub-bass below 30 Hz, level doesn’t roll off. Given that, the bass is present, however definitely not over-accentuated and fits in coherently, as there is no unnecessary fundamental tone bloom.
The mids around 1 kHz are broad-banded emphasised, with a somewhat greater focus on the upper mids, bringing out (especially female) vocals’ details a bit more, but also slightly accentuating sibilants if the recording isn’t super clean. Tonally, the mids are mostly correct in my ears, with just a minimal tendency to brightness (for reference, DN-2000J’s mids are minimally brighter than FLC8s’ in my ears). From the presence area above 2 kHz on, level drops evenly and forms a greater recession around 5 kHz which guarantees for good long-term listenability without fatigue and with unobtrusive mids; that’s why many in-ears show a somewhat similarly distinctive dip around 5 kHz, for example the Fischer Amps FA-3E whose dip in the middle treble is about identical to FLC8s’ (a good thing is that it isn’t as distinctive as W4R’s dip which adds a bit too much smoothness and relaxedness to the highs and mids with a tendency to mugginess; FLC8s’ middle treble character is just “normal with a somewhat relaxed, non-obtrusive character” and clean plus detailed). From 6.5 kHz on, level starts increasing again and forms a peak in the upper treble at 8 kHz which is marginally above the ground-line and not annoying at all. Super treble extension is still good, with even level up to 12 kHz and an even roll-off from there on. Subtle “glare” above 10 kHz is still audible and I actually don’t miss anything in terms of treble extension, although there are some multi-BA in-ears that reach even higher in the treble before the roll-off begins.
For daily use, this kind of tuning appeared to be quite enjoyable – the bass is somewhat accentuated but not too much to become obtrusive, but is just there to add a little weight, vocals come through very clearly due to the moderate emphasis and sound very clean, the somewhat recessed level in the middle treble guarantees for a good long-term listenability without fatigue and the slight emphasis in the upper treble is just lightly noticeable, though percussions sound slightly brighter.


 02: Grey/Clear/Blue:
With this filter combination, I would describe the sound as quite neutral with smooth, dark treble.
The bass is slightly more present than with a Clear/Clear/MF-HF combination (ca. 2 dB north of neutral below 80 Hz), though the benefit is that it doesn’t roll off in the sub-bass with this filter combination. Here, the mids show a slight broad-banded emphasis, too, though there is no emphasis in the upper midrange and vocals are on the darker as well as more relaxed side, without any signs of sibilance. The middle treble is somewhat in the background as well, though even a bit more than with the gold MF/HF filter, so the impression of a smooth, relaxed midrange and treble is even stronger (for my personal preference, it is even slightly too relaxed and heads into Westone W4R’s smoothness in the upper frequencies). The upper treble is now also clearly in the background and darkens the sound.
If you love a balanced bass and midrange with a downwards-slope in the highs, this tuning might be for you.

03: Red/Black/Blue:
With this filter combination, sound is an evenly down-sloping curve from the sub-bass to the upper treble and slightly reminds me of the reference curve for car-hi-fi.
Again, the emphasis in the lows starts at around 500 Hz and then increases very evenly with a straight line, without any hump, towards sub-bass where level is about 9.5 dB north of neutral at 30 Hz. The midbass is a bit less present and so is the upper bass with about 5.5 dB, with an evenly decreasing fundamental tone area. As a result of this characteristic, the bass fits in nicely and unobtrusively, without too much upper bass kick or fundamental bloom, as the emphasis is mainly in the mid- and sub-bass. Accordingly, the lows also commendably stay away from the mids.
The midrange is not slightly emphasised anymore here with this filter configuration and is, just like with the previous Grey/Clear/Blue filter combination, somewhat on the dark, relaxed side. Treble is identical to the previous tuning.
For a smooth, relaxed, bass-emphasised tuning with “cellar rumble”, this tuning is well-suited.

04: Red/Grey/Gold:
This filter combination focusses more on the sub-bass, along with bringing a detailed midrange and correct treble into the game.
The lows more or less resemble the previous Red/Black/Blue filter combination, however with this Red/Grey/Gold configuration, the sub-bass shows to advantage more as both the root as well as upper bass are slightly less present. The bass kicks a bit less and concentrates more on the “cellar rumble”.
The mids around 1 kHz are just very minimally lifted and sound tonally correct in my ears.
The middle treble is about identically in the background as with the first (Grey/Grey/Gold) combination and gives some smoothness and good long-term listenability without fatigue. The upper treble sounds quite natural and as well as not emphasised, but straight to the point.
For a sound with balanced midrange and treble plus elevated sub-bass with less upper bass and fundamental tone, this filter combination works very well.

05: Red/Black/Green:
With this filter combination, the sound of the in-ears follows a v-shape.
The bass is quite identical with the third filter configuration (Red/Black/Blue) and expresses itself with a somewhat emphasised “regular” low-range with upper bass and fundamental tone area, with the greatest focus being in the sub-bass.
The mids around 1 kHz are just very marginally emphasised and in total view, when incorporating lows and highs, vocals are even a bit in the background and also sound somewhat thin, however neither hollow nor low resolving.
The middle treble is audible less in the background with the green filter; the upper treble at 8 kHz shows a distinct peak which is however still humane and not too sizzling or piercing as long as one isn’t listening at very loud volume levels. Nonetheless, sibilance is more emphasised and some recordings get the tendency to be a bit annoying and hot.
For lovers of v-shaped signatures, this filter combination might be well-suited.

06: Clear/Clear/Gold:
This filter combination is one of the recommended in the quick-start guide and is labelled as “Vocal” – for reason, as it really is a signature that focusses on voices.
The bass is rather lean and mostly neutral, at least in the upper midbass, upper bass as well as lower and upper root area. In the middle fundamental tone, there is a minor emphasis; the bass starts evenly rolling off from about 50 Hz.
The mids are in the foreground with this tuning, with a preference of the upper midrange, wherefore this filter combination is well-suited for female vocals. Male singers however sound a bit thin.
The treble is identical to the first (Grey/Grey/Gold) tuning.
For tracks with mainly female singers, this tuning is recommendable if one wants to bring out the voices some more.

07: Grey/Clear/Gunmetal:
This is the filter combination that I see as reference tuning for the FLC8s, and as somebody who loves neutral sound and sees the Etymotic ER-4s as the best example of how neutral tonality should be (the ER-4S is even closer to ideal neutrality than my custom-moulded UERM), I can also say that the FLC sounds pretty neutral with this filter combination and comes quite close to ER-4S’ tonal tuning.
Upper bass, midbass plus the lower fundamental tone are very marginally more present than with a Clear/Clear/Gunmetal combination which however suffers from a moderate sub-bass roll-off, wherefore I see the Grey/Clear/Gunmetal filter combination as the more reference-like. Otherwise sound is free from any unnecessary warmth and the bass is very even, “flat”, without real emphasis.
The mids are pretty spot-on and tonally correct in my ears, without colouration.
The middle treble is somewhat in the background as well, however very slightly less than with the gold filter and therefore seems a bit less relaxed. With this filter combination, the upper treble is also just very slightly, though inconspicuously above the ground-line.
For a rather sterile, very neutral sound, this filter combination is quite ideal (and I personally love it).

For the following comparisons, I used the first and seventh filter combination most of the time.


The resolution capabilities of this in-ear are simply stunningly high for the price and I go that far to say that the FLC8s can compete with my UERM in the midrange and treble department without problems. In the highs, the UE is very slightly more differentiated plus refined and also a bit more realistic despite its peak (in comparison, the FLC sounds slightly constrained/dull in the upper treble), but in the mids both in-ears are about on-par and honestly speaking the FLC8s sounds even more detailed in the vocal area, as it reveals more minute details while sounding very easy-going, precise and natural. Even after about two months of almost daily use, these in-ears still manage to positively impress me with their very good technical capabilities and detailed, silky midrange. Tiny details in the treble and mids are no problem for the FLC8s and fine details are presented and revealed in a very easy-going, natural way. I guess I don’t even have to mention that speech intelligibility is extremely high, as that should be clear from the context.
In the lows, it looks a bit different, but that is simply because of the different driver types: although FLC8s’ bass is very fast and precise, it doesn’t reach the precision, control and details of UERM’s Balanced Armature driver when very fast and complex tracks are being played. FLC8s’ bass character is quite typical for a (really good) dynamic driver and it is not too hard to tell that it is no BA woofer, but on the other hand, this dynamic woofer driver is very detailed on its own and sometimes, especially with less complex and rather slow music, it is quite difficult to say whether it is a dynamic or BA driver, although the bass doesn’t stand in the room straight to the point but is a bit more space-filling.
What Forrest Wei has created hare is a really detailed, technically very capable and brilliant in-ear that has enormous cohesion between the three drivers which harmonise perfectly together, so that the dynamic driver fits in perfectly and doesn’t appear even at the slightest negatively but just somewhat more corporeal and less “sterile”.


The sole area where the FLC8s could yet fail is the soundstage, but it also copes with this discipline with ease: FLC8s’ soundstage is quite large in terms of lateral expansion and about comparable with the one of my UERM. Therefore, width is also somewhat wider than DN-2000J’s stage (though not by much). There is also a good amount of depth, though it is just about one quarter less distinct than width, wherefore soundstage isn’t as deep/almost bottomless like the DUNU’s or UE’s. When it is about three-dimensional presentation and naturalness, the FLC leaves a very positive impression and sounds harmonious.
Regarding instrument separation and spatial precision, the in-ears are technically really strong, as single elements, even if they are yet so small, are super precisely separated – almost as precisely as with the UERM. And as a result, the FLC8s even manages to separate and place instruments slightly more precisely than the DN-2000J which already does a really good job here.


In Comparison with other Hybrid In-Ears with three-Drivers-three-Ways-Configuration:

Oriveti Primacy:
The Oriveti Primacy is a really good and convincing hybrid in-ear with a smooth yet detailed and (in a very positive way) non-exciting sound as well as superb build quality. When it is about sonic strengths, the Primacy comes very close to the DN-2000J, which speaks for its sound quality. However, the FLC8s manages to unveil even more details in the midrange and treble, in addition FLC’s dynamic woofer is even better and more cohesively integrated to the system as it is almost just as good as its two brilliant BA drivers for the mids/highs (Primacy’s lows are very slightly less detailed than its mids and highs although sound is harmonious and coherent, too).
FLC8s’ soundstage is a bit wider than Oriveti’s and has especially got somewhat more depth. In terms of instrument separation, -placement as well as spatial precision, the FLC is also the winner.

DUNU DN_2000J:
The DN-2000J is an extremely good in-ear and convinces inter alia with its special bass which is both very fast and precise as well as tactile and has a gorgeous body at the same time (its lows’ qualities are quite similar to my Audeze LCD-X’s). On top, midrange and treble resolution are excellent.
Well, the FLC8s reveals even a bit more details than the DUNU and also has got a minimally faster bass which is more arid too, although DN-2000J’s is already really good for a hybrid in-ear. What the FLC however doesn’t adopt is DUNU’s woofer’s special character which is albeit something very unique for itself – in exchange, FLC8s is overall sonically and technically the somewhat better and slightly more refined, detailed in-ear.
FLC8s’ soundstage is a bit wider than DUNU’s, however less deep. In terms of spatial presentation and instrument separation, the FLC is somewhat more precise, with instruments that are very cleanly placed and sharply separated from each other – even more than DN-2000J’s.

UPQ Q-music QE80 (OEM Version of the Fidue A83):
Without any doubt, the FLC8s is the more versatile IEM with its theoretically possible 36 different tonal tunings, but will always have less fundamental warmth than the QE80.
The FLC, of which I think is overall very slightly better than the DUNU, also surpasses the UPQ. The FLC8s has got the faster and more arid lows than the QE80, which on the other hand puts out the nicer bass body (this however goes at the expense of speed). When it is about resolution, the FLC is somewhat better as well, even in the midrange.
Solely QE80’s upper treble sounds a bit more natural and realistic as it is more broad-banded.
The FLC’s soundstage is slightly wider, with about identical depth. In terms of spatial precision, the in-ear with 36 faces wins as well.
Victory (however not a big one) of the FLC8s in every aspect expect for upper treble naturalness.


The FLC8s is not only an extremely good hybrid in-ear but also definitely a hybrid flagship. The in-ears are very convincing with their precision, soundstage, resolution (especially in the midrange – vocals sound so clear, detailed and realistic that they even slightly beat my UERM’s) as well as versatility. Surely the knowledge of having 36 potential sound signatures is really cool, however realistically seen, one will more likely have up to four filter combinations that are probably slightly tweaked from time to time. One also has to be careful with the any filigree filters, as they can be lost easily given how small they are – in this regard the FLC8s is more an in-ear for enthusiasts than a product that is suitable for the masses, but I personally find it good that way as it shows how much is technically possible with the various filters.
What unfortunately doesn’t fit to the sound which can be almost seen as being on the same level as the UERM is the cable which is very microphonic for a model of its kind.

Sonically this in-ear scores 5 out of 5 stars with brilliant ease – with a 70%-sound-to-30%-rest-weighting however, the FLC8s “only” manages to score 4.5 out of 5 stars, which is quite sad, as with a less microphonic but more flexible cable, this would be unquestionably a 5/5 product. But even so, the in-ears get a really distinct recommendation for their sonic qualities and two thumbs up.
Thank you very much for the reply. It really is a tough choice especially after reading up on the Oriveti. I checked the website for the FLC8s and I assumed it was US dollar. I guess I cant go wrong with any of those?
Ah, the price you mentioned is in SGD on the LMUE website, you have to switch it to USD in the upper right section of the page.
Ok thanks for that bud. It makes a huge difference in price.


100+ Head-Fier
Pros: Unbelievable Coherence, Distinct Airiness, Endless Customization/Tunable Options, Lightweight and Solid Construction, Aluminium Carrying Case
Cons: Tuning Ports/Filters are fragile, Tedious Tuning
Before I start on my endless tirade on this hidden gem, allow me to make a formal introduction.
My Formal Introduction
I'm a 19 year old (coming 20) Singaporean Student waiting to serve my Mandatory Army Service. I grew up captivated by music and its divergent genres. From subversive punk (The Germs, Black Flag) to the Mellow Jazz Cats (Miles Davis, John Coltrane), I was always fond of music history and the preceding factors that led to the formation of several bands and genres. Ever since my brother brought me to Jaben in its glory days (in a crummy, old warehouse with a pile of imported iems), I started to stick my itchy fingers into the personal audio market. I'm no audiophile, but I'm just here to give my two cents on products that I find far more than capable at a suitable price. I despise the lifeless sound of a Balanced Armature on its own. The unnaturally faux left to right soundstage and the rigid/dry bass response always irked me. Hybrids and Dynamic Drivers will and always be the top tier transducer/combinations in my heart. 
Alittle Bit of Backstory
FLC Technology is a company based in Guangdong, China. Opened by Forrest Wei (correct me if I'm wrong), a industry regular that has worked with the likes of UE and Jabra, the FLC 8 is their first foray into the Universal IEM Market. Launching their first CIEM in 2011, FLC Technology hopes to make a name for itself in a congested IEM Market. The FLC 8S is an exact cut/copy replica of the FLC 8, provided with a 4-braid SPC Cable instead of the poorly sheathed cable by its predecessor. Forrest believes that the consumer should have a say in the sound signature of any IEM, hence the provision of tunable filters.
The FLC 8S is a hybrid in-ear monitor, with a 2 Balanced Armature + Dynamic Driver (3 Way Crossover) configuration. The FLC 8S boasts a whopping 36 tunable options, setting itself apart from the competition. China is making a name for itself in an already crowded IEM market dominated by the big three (Shure, Audio Technica and Westone). I'm proud to report that the FLC 8S is a top tier contender that blows the competition out of the water. They are a diamond in the rough, a hidden gem waiting to be discovered.
Build Quality/Accessories
Right off the bat, the lavish wooden box looks downright expensive. FLC definitely went out of its way to package the product beautifully. Inside the box, we have several eartips (S,M,L), a anodized aluminium rounded case (this crap is built like a tank) and a keychain carrying the different filters and nozzles. The accessories provided are impeccable and feel almost premium, rivaling the likes of the Shure SE846. Gotta give a shoutout to FLC for giving us a premium package at an affordable price point.
Moving on to the IEM's, they look almost alien-like. The driver-housing or the actual body of the IEM's are shaped like curved S's, with a glossy finish. There are several ports or tiny holes to allow the user to interchange filters and try out a variant of sound signatures. Apart from the outlandish appearance (at first), the IEM's are feather-light with negative profile. The flushed fit and lightweight housing provided me with a comfortable listening experience. It's as if the FLC 8S melds with the ear to become a unified body. I've used them for over 3 hours straight with no signs of discomfort or fatigue. They feel solid in the hand and I have no doubt's that they were built to last for a long time.
The cable termination is a recessed 2 pin connector (the UE Triple -fi connectors), which are easily user replaced. Having said that, the stock 4-braid SPC cables provided marked a significant improvement compared to its predecessor, which provided a rubber-sheathed cable with stiff strain reliefs and a bad tendency to clump into a giant ball. They are easily pliable and the memory wire offsets the weight off the IEM onto them, acting as a strain relief.
I have to say, I am duly impressed by the overall build and accessories provided.
Sound Quality
I have to say, these IEM's are absolutely stellar. Admittedly, these are IEM's are ever changing chameleons, with 36 tunable options that leaves the user baffled by its ability to adapt. I for one, value my time and choose not to review every single combination. Having said that, the combination I have utilized centers around a heavy low end, distinct mid range and medium high frequency (minor filtering). Do take note that the tuning process has a steep learning curve. Time and patience must be exercised to find a suitable combination that meets your tastes. Its time for me to dive head first into the delicate art of finding the right "sound".

Credits to Lendmeurears for the image
- Black Filter: Medium Mid Range and High Frequency
- Green Filter: Medium Mid Range and Most High Frequency
- Blue Filter: Medium Mid Range and Least High Frequency 
- Gold Filter: Most Mid Range and Medium High Frequency
Rubber Stoppers (white, black grey)
- White Stopper: Medium Bass
- Clear Stopper: Least Bass
- Black Stopper: Most Bass
Rubber Thumbtacks (lol)
- Clear: Least Subbass
- Black: Medium Subbass
- Red: Most Subbass
As you can see, the art of finding the right sound can be tedious. It makes for a fun project though. Be wary that the intricate filters are tiny and easily lost. Thankfully, Lendmeurears Singapore stocks replacement filters at a reasonable price.
As of now, I'm utilizing the Gold Nozzle => Black Stopper => Red Thumbtack Configuration. It focuses primarily on a creamy mid range, smooth highs with ample detail and a airy bassline. 
The FLC 8S left me floored. Balanced Armatures are known for their distinctly sharp mid range, extended highs and accurate/rigid response. The addition of an 8.6mm Dynamic Driver offsets the weaknesses of the 2 Balanced Armatures by providing a robust bassline and superb subbass decay. What boggles my mind is the coherence of it all. I believe that transient smearing and the use of 3-4 balanced armatures with no dynamic driver results in an incoherent, artificial sound that feels vastly separated. The unnatural left-right channel separation (faux soundstage) and crummy low-end response doesn't leave me satisfied. This is certainly not the case for these hybrid badboys. 
The Gold Nozzle tames the highs and smoothens the peaks, but it does it in such a way where the highs aren't sibilant and provide just enough detail. With tracks such as Charles Mingus's Moanin, the baritone saxophone barely loses detail and in fact sounds almost natural (apart from minor smoothing)
The Midrange is rich, easily distinguishable and detail heavy, with a non-fatiguing wet sound that avoids the harsh trebles and sharp mid-ranges commonly associated with balanced armatures. It provides for a non-fatiguing listen for any genre. It's even listenable with the sharpest of treble-heavy genres such as Hardcore Punk. That is an achievement on itself.
The low end is the highlight of the FLC 8S that separates the men from the boys. Using the Black Stoppers and Red Thumbtacks, the sumptuous low end proves to be well controlled, with a tight midbass response and sublime subbass decay. Most importantly, the bass in my opinion, doesn't bleed into the mid range at all, leaving us with a fun/controlled bass response that faithfully captures the air and stage presence of any given recording.The FLC 8S is a forgiving IEM, even with 128kbps MP3 Files.
In Conclusion
The FLC 8S is a representation of Chinese innovation. Over the years, I have seen the growth of many a Chinese Audio Company, each trying to tap into the Southeast Asian market. Some companies left me impressed (Vsonic, Havi) but nothing blew me away. The FLC 8S has done just that. Their penchant for perfection in sound, build and customization is a testament to Chinese quality. I would've given them a perfect score, if not for the fragile tuning components. I certainly hope that people give the FLC 8S's a shot and be mesmerized by their sound.
Just received a pair; really, really like them.
Black+Red+Gold Master Race
Thanks, which one is better choice? DUNU 2002 or FLC8s?


Headphoneus Supremus
Pros: Sound can be fine tuned to listener preference. High fidelity at reasonable price point.
Cons: Difificult to insert filters. Easy to lose filters. Moderately easy to get ear fit but not dead simple. Tuning could be "overkill" for some.
I had the pleasure of listening to the FLC8S for about 10 days. 
I listened to these on a FIIO X3 Gen II, a Shanling M2, and the venerable iphone 6S.   My comparison is to LZ-A2 using Comply foam tips, Phonak Audeo PFE-022 with black filters and Comply foam tips, and Carbo Tenore using stock tips. 
I listened to a wide variety of music, including Rock, Jazz, and Classical.  Something that surprised me was that I could listen to all varieties of music with these and get a pleasurable experience.  Normally I reserve the Phonaks for classical, where bass is not as important and musical accuracy is important.  But with these I was very happy no matter the source material.
They sounded very good with all players, but were especially terrific with the Shanling M2.  The Shanling is a very neutral and clear sounding unit, and really brought out the best in these earphones.
I found myself noticing the clarity of instruments, yet easy shifted to simply enjoying hi res music.  There is a reason these IEM units have developed a buzz; it is simply not just hype. The detachable cables can come loose fairly easily, so I would be careful with the units when used in public areas.  I stuck mainly to the blue cables though I did try the other two cables that were in box.  Somehow I preferred the blue cable comfort and stuck with those.
My overall conclusion is that these provides an exception level of audio quality with a high degree of customization.   I mainly fiddled with the low bass, as I was very happy with the stock tunings. The effect was subtle but helpful to add sub bass.
It is interesting to me that most other reviewers of this headphone also seem to go with the stock tunings, with the possible exception of adding more sub bass.  That is because these IEM units have an essential “rightness” to them right out of the box.  
Customizing these IEM units is not super easy.  As other have mentioned, the small rubbery plastic inserts are difficult to manipulate and go flying about.  I would suggest working on a clear table and not over carpet.  Pieces can and will go missing.  I ended up using the tweezers to remove the tuning devices but put them in by finger. 
My overall suggestion is that the manufacturer consider offering a cost reduced version of these with the base neutral tunings with the exception of somewhat tweaked sub bass.   I think a more basic version with this sound signature at the right place could become a monster product.  I realize the tunability put the manufacturer on the map, but now that they have a name I would readily purchase a cheaper, less tunable version. 
I would also suggest studying the fit of the Carbo Tenore, which somehow gets the sound right in a very comfortable to wear format.
These are exceptional IEM units and my sense is that improvements on these will ultimately be about fit, comfort, and price and not about sound quality.
originalsnuffy, you nailed my impressions almost perfectly. You have a good ear
and a sense of what is important! good listening and writing, thanks for the additional
insights also into possible future budget versions of these that keep the essential
goodness of this IEM!
Thank you Dr. Blue.  I started off with the tuning that you were using and did not stray too far!
Paulus XII
Paulus XII
Interesting reading originalsnuffy. Always appreciate other trained ears people thoughts of FLC8S. It's still my favorite IEM.

d marc0

Headphoneus Supremus
Pros: Tunable with 36 sound variations, comfortable fit, good sound performance
Cons: short cable, tiny-easy to lose parts
Hybrid In-Ear Monitors (IEM) now have their own fanbase following the emergence of the first universal high-end one in 2011. Earphone manufacturers recognised this and have since produced their versions of the hybrid configuration: Dynamic Drivers for bass + Balanced Armature Drivers for midrange and treble. I’m proud to say that I am a bonafide hybrid IEM fan. The benefits of having both dynamic and balanced armature drivers in one IEM are unique, almost impossible to replicate with a single driver design. Dynamic drivers offer a natural bass timbre; add that to the superior midrange-to-treble clarity of balanced armature drivers, the end result can be fantastic! That’s If they tuned it right… easier said that done.

Aside from the hybrid driver configuration, adjustable sound or tuning has become a common feature amongst in-ear monitors. We’ve seen interchangeable tuning filters that can alter the upper midrange and high frequency responses. Other models have bass rings that will cover bass vents, therefore increasing the bass impact and sub-bass extension. In the case of FLC Technology’s hybrid IEM, three tuning methods were utilised, allowing various combinations to shape a sound signature that’ll match your preference. So here, we have the FLC 8S – the hybrid in-ear monitor with tuning capabilities of up to 36 sound variations.

RETAIL PRICE:           US$ 335
DRIVER SPEC:           8.6 mm dynamic + dual balanced armature drivers
IMPEDANCE:              11 Ohm
SENSITIVITY:              93 dB/mW
FREQ RESPONSE:    20Hz – 20KHz
TERMINATIONS:        2-pin, 3.5 mm gold plated L-plug
INCLUDED CABLE:   1.3 M TPU cable, 1.3 M OFC copper cable
WHERE TO FIND:      lendmeurears.com

Disclaimer: This review unit was provided as a loaner. Special thanks to @DJScope for facilitating the tour.


FLC Technology did a decent job on the FLC 8S’ accessories. It shows that lot of thought came into play before finalising the retail packaging. However, I do think that a few more variations of ear tips and a shirt clip to assist in minimising cable noise (microphonics) could add more value to the overall package. Other than that, all the accessories that made the retail packaging are there to ensure good user experience.

  1. 8 pairs of silicon tips (S,M,L)
  2. 1 metal case
  3. 1 pair tweezers
  4. Low frequency tuning plug: nine (three groups, one group of three)
  5. ultra-low tuning plug: nine (three groups, one group of three)
  6. Tuning catheter: eight (four groups)


iPod Touch 5th Gen > OPPO HA-2 DAC/AMP
16/44 FLAC and ALAC
T-PEOS hybrid silicon ear tips were used

Dr. Chesky’s Ultimate Headphone Demonstration Disc
Booker T. Jones – Representing Memphis
Seductive Souls – How It Feels
Pantera – Domination
Daft Punk – Giorgio By Moroder
Sia – Chandelier
Jewel – Somewhere Over The Rainbow

I really like the design and build of the FLC 8S. At a glance, it doesn’t look premium, but upon closer inspection, the plastic housings have a nice, smooth finish with no noticeable gaps. What’s obvious are the unique tuning ports, where the tuning plugs reside and the blue coloured theme from the housing, all the way to the tip of the cable. There are two different types of cables included, a black stock TPU cable, and the OFC copper cable which has the blue colour scheme. The black stock cable may look plain but it’s supple and lightweight. The lack of stiff ear guides make them the cable of choice for those who wear glasses. The aesthetically more pleasing OFC copper cable has a more sturdy build but it’s slightly stiff and retains some memory (shape). The blue cable is quite microphonic (cable noise) when rubbed onto clothes but easily minimised by attaching a shirt clip. Cable length can also be a concern because they seem a bit too short by today’s standard. The shape of the housing may not look the part but they conform to the shape of my ear. Inserting the IEM is very easy, and they sit securely like conventional ear plugs. I also find them very comfortable even after a few hours of listening sessions. Please note that your mileage may vary because we all have different ear shapes and sizes. I have small to average-sized ears so these IEMs will surely fit the majority.


The tuning feature on the FLC 8S utilises three different adjustments, which sets this IEM apart from its hybrid counterparts. Four sets of tuning catheters can be interchanged and attached on to the nozzles; these are responsible for tuning the midrange and treble. To adjust the bass quantity, three sets of low frequency plugs are available for the front tuning ports. Last but not the least, three sets of ultra-low frequency plugs can be used to adjust the sub-bass extension. Mix and match… you’ll find 36 various combinations with noticeable difference in sound signature. At the end of the day, I believe  most users will stick with one or two combinations to match their preferred sound signature. My personal favourite is the recommended default combination: Gray Ultra Low Frequency (ULF) plug + Gray Low Frequency (LF) plug + Gunmetal (MF/HF) Nozzle catheter/filter. Please take note that the tuning plugs are very tiny and can easily be lost or misplaced. Changing the sound signature is a fiddly process and requires a proper setting to avoid losing parts. A pair of tweezers is included as a tool for installing the tuning plugs; please do not attempt to use the said tool for facial grooming *wink*.





For the purpose of this review, I will be using the recommended default combination. This can serve as a reference for FLC 8S users; and by using the description of the tuning accessories above, one can estimate the effect of interchanging specific tuning plugs or nozzle filters. The sound presentation for the default combination is the most “balanced” when compared to the other combos. The Gray ULF and LF plugs’ effect is a slight accentuation in bass. The Gunmetal MF/HF catheter or nozzle filters effect on tuning is a neutral midrange with a smooth upper midrange; while the treble has a slight emphasis that projects more energy and extension.

Most people seek a great bass response before anything else in the frequency spectrum. The same holds true for Hybrid IEM fans, the bass performance holds a massive influence on the buyer’s decision. Fortunately, the FLC 8S holds its own when it comes to bass control, texture, and layering. The test track used for this section was Giorgio By Moroder by Daft Punk. The details come through clearly with every bass guitar line and drum beat. Sub bass rumble is sufficiently felt. Timbre is quite organic and natural sounding, so differentiating various instruments is not a hard task with this IEM. The transition from bass to midrange is seamless, another testimony on the FLC 8S’ competence in keeping the midrange clear of bass bleed. While not the best in the market, the FLC 8S is competitive enough in its price range. Since this is a review, I’m going to nit pick and determine key areas for improvement. The bass decay times seem a tad bit slower than other high end IEMs. Bass tightness could also be improved to uplift its sense of urgency. Really minor nit picks but these shortcomings are noticeable when listening to fast bass lines or drum blasts. Pantera’s Domination from their debut album is an excellent track to demonstrate bass speed or decay times.


Midrange is akin to the meat in a burger. It’s the main focus of the entire experience and the FLC 8S is as tasty as good burgers can get. Instruments and vocals sound naturally life-like. What impresses me is its ability to smoothen the upper midrange to relieve poorly mixed tracks of potential harshness. Sia’s all-time famous Chandelier is a track I use to test upper midrange control. Too much boost in this area and it’ll sound harsh, edgy and fatiguing. The FLC 8S manages to keep a more pleasing presentation, devoid of potential harshness. On the other hand, clean sounding tracks with piano or female vocals as a centrepiece might leave you wanting for more presence. Jewel’s rendition of the classic – Somewhere Over The Rainbow, presents an intimate vocal performance but clarity and definition seem to take a back seat when listening through the FLC 8S. Not quite noticeable but something to take note of if you’re a critical listener. Overall midrange balance is good and quite enjoyable for most modern music.


I prefer the treble response to have ample energy, airiness and extension. Well, I’m happy to report that the FLC 8S passes with flying colours although with a caveat. There’s a slight over-emphasis in the treble response making the presentation a bit brighter than intended. Scratchiness and sibilance can be an issue at high listening volumes or brightly mixed recordings. Take Daft Punk’s Random Access Memories as an example. The entire album was intricately mixed and mastered that sibilance is non-existent even on the FLC 8S. Put in some early 90’s rock tracks and you’ll immediately hear the exaggerated SSS’s and cymbal crashes. As long as you’re particular with song selection and stick with quality recordings, the FLC 8S will continue to impress.

Overall sound presentation from the FLC 8S is effortlessly grand in scale; more on the width of the soundstage rather than depth. Spacing between instruments or musical cues is above average, better than most IEMs in this price range that I’ve tried. Imaging could’ve been better if there was more depth but at least it’s good enough to maintain a cohesive presentation. The recommended default configuration has a nice, balanced sound signature. The low end frequency response is slightly on the warmer side of neutral. The mild accentuation in the treble region complements the low end warmth and helps maintain the overall balance. Listening to Seductive Souls – How It Feels, was quite a euphonic experience.


The FLC 8S is a well featured high end hybrid IEM, thanks to its tuning capability. I don’t expect anyone with the FLC 8S to be changing combinations regularly, but it’s a good option to have when you feel the need. I would recommend the FLC 8S to those who are planning to upgrade from a beginner’s setup but unsure of their sound preference. Having the option to customise the sound to your liking is the safest way to avoid regrets in portable audio purchases. It is also a great solution for people who have hearing loss or sensitivity in specific areas of the frequency response. The FLC 8S is flexible enough to attenuate or accentuate certain frequencies that can help improve the user's listening experience. So it is important to try all the tuning combinations to find the sound variation that's perfect for you. I surely hope that FLC Technology will continue to innovate and produce wonderful products. They are already on the right track with the FLC 8S and a few more minor tweaks to the sound will move this product forward to top-of-the-line status.

NOTE: The ratings meter above is inaccurate. It should be:


Thanks, I'd like a comparison with the Savant :)
d marc0
d marc0
@Rollk2  You're welcome. It's quite hard to do a decent comparison because of the type of drivers and the various tuning. In general, the Grey ULF + Grey LF + Gold mid-hi is the closest in terms of signature. Bass on the Savant is tighter and nimble, while FLC has more depth and sub bass extension. Mids is quite similar between the two but the Savant has more laid back lower mids. Treble is where there's quite a difference. Savant is smoother while FLC8 has more energy and extension. Overall control is more refined on the Savant, the FLC8 can get a bit aggressive on some tracks. Hope that helps.
Thanks, which one would you buy? DUNU 2002 or FLC8s


500+ Head-Fier
Pros: Sound, Build
Cons: Microphonics
[Update] 19-Mar-2016 Added comparisons
     I have had the FLC8S for about 3 months but never had the time to sit down and write a review until now. Before proceeding further, I would like to thank all the reviewers and fellow Head-Fi members from the FLC8S thread [link] who initiated my interest in this product.

7ofR4dc.jpg  W6aDsMS.jpg
hmE3PC8.jpg  2wlfqqf.jpg
The IEMs and the Tuning Filters
1 Preliminaries  
1.1 About Me
     I am a student in pursuit of a master's degree. I got interested in audio equipment rather recently. I am not the usual reviewer and I have spent most of my time here lurking around looking for answers. So, please pardon me in case some things are out of place. In any case, I am looking forward to feedback from the community to try and improve things in the future. The opinions that I have provided in this review are purely based on my listening experience and not any graphs or numbers.

1.2 Preferences
     I like a balanced sound signature with good detail reproduction. I have a slight tendency to like bright-sounding headphones as long as they are not too harsh or sibilant. As far as musical preferences go, I am a bit of a metalhead.
2 Product Overview
     The FLC8S is a triple driver hybrid IEM with a unique tuning system that allows one to tweak the base sound signature in 36 different ways through the use of different filters. On each side, there is a single 8.6mm dynamic driver and dual balanced armature drivers. It has been some time since the original FLC8 became available online. The current iteration, the FLC8S, comes with braided cables.
2.1 Packaging and Accessories
The following accessories are included as a part of the standard packaging.
  • Two sets of silicone tips in SS/S/M/L sizes.
  • Three sets of ultra-low and low frequency filters.
  • Two sets of mid-high frequency filters.
  • A 3.5mm to 6.5mm adapter.
  • A balanced to 3.5mm adapter.
  • A cleaning tool.
  • A keychain with a fob that houses the filters.
  • A metal case.
  • A pair of plastic tweezers.
  • An instruction manual.
2.2 Design and Fit

     I liked the way the box opens up. The materials aren't anything exotic. Everything is rather well organized inside the box. The compact manual has most of the details about the tuning system. The included metal container is very solidly built. So is 6.5mm-to-3.5mm adapter. Each of the two sets of tips, one clear and the other gray, come in SS/S/M/L sizes. The quality, quantity and variety of the supplied tips are pretty decent. The filters are neatly housed inside the keychain's fob. The bass filters are rather tiny and delicate so they might need an extra bit of care when swapping parts. This makes the inclusion of an extra set of the ultra-low and low frequency filters somewhat relieving. The filters, once attached, all sit firmly in place. The IEM housings are lightweight and well-built with decent finishing. The cable is a bit too stiff though. The 2-pin connectors require a bit of effort for removal but nothing herculean. Also, since they have been confirmed to be TF10 compatible, there should be lots of options for those looking for cable upgrades.
     The only major gripe that I could have of the FLC8S is the cable's proneness to microphonics. Also, for people with small ears, the IEMs stick out a bit and it becomes a little difficult to get the stiff memory wire to settle down properly. When it comes to the chin slider and y-split, I want something sturdier instead of simple plastic sleeves. Apart from these, I have no other issues with the fit and isolation.
2.3 Tuning system
     There are three different types of filters for sub-bass, bass, and mids and highs adjustment.
  • Ultra-low frequency (ULF) filters
    • Clear - Minimum
    • Grey - Medium
    • Red - Maximum
  • Low frequency (LF) filters
    • Clear - Minimum
    • Grey - Medium
    • Black - Maximum
  • Mid + High frequency (MHF) filters
    • Blue - Medium + Minimum
    • Black - Medium + Medium
    • Gold - Maximum + Medium
    • Green - Medium + Maximum

3 Testing
3.1 Setup
     For this review, I used a FiiO X3 1st Gen + E12A stack as the source. The X3 was connected to a PC as a USB DAC. For playback, foobar2000 with the proper ASIO drivers was used. Prior to writing this review, I had already used the IEM for over 200 hours.
3.2 Sound Quality
     Coming from the GR07 and VC1000, both of which are fantastic units from VSonic, when I listened to the FLC8S for the first time I was rather impressed. It offered better mid-range and treble quality compared to the GR07 and better bass, both quality and quantity-wise, than the VC1000 whilst matching or even improving on its mid and highs. At first, the highs sounded a bit metallic but I think with time, it now sounds much more natural. I started listening with the stock M sized tips and a pair of M sized SpinFit tips before reviewing. For this review, I used the stock tips.

3.2.1 Lows
     With the dynamic driver taking care of the bass, the decay is very natural; neither too fast nor too slow. There is enough impact and control when needed and it goes pretty deep too. Quantity-wise it is a little above neutral with the default Grey ULF, Grey LF filters. The combo of Red ULF, Black LF filters offers the maximum bass. Even in this configuration, the mid and high frequencies are still clearly audible. I was particularly impressed with the way it managed to keep up with the fast-paced bass of some death 'n' roll tracks. It also managed to keep the chilling atmosphere in some raw black metal tracks without adding any noticeable warmth. It really shows the level of control that is on offer. Initially, I often switched between the Grey ULF, Grey LF combo and the Red ULF, Gray LF combo and ended up preferring the former. The Red ULF filter adds a little more impact but I found the Grey ULF filter to be satisfying in most cases.
3.2.3 Mids
     Throughout the review process, I used either the Black or the Gold MHF filters. I felt that the Green MHF filter affects the naturalness of the vocals. The Blue MHF filter seems to make the sound dull and less energetic. In most cases, I ended up preferring the Gold MHF filter. It makes the mid frequency feel a little more present and sound forward compared to the Black MHF filter. With the Black filter, the mids are smoother but the Gold filter provides a bit more detail retrieval.
3.2.4 Highs
     The high frequencies sound crisp and energetic without any noticeable sibilance issues with the Black and Gold MHF filters. The Blue MHF filter cuts down the treble presence while the Green MHF filter introduces some sibilance. For classical-inspired instrumental pieces though, I sometimes found myself reaching for the green filter. The speed, decay and airiness are all top notch. Acoustic guitars are a joy to listen on this.
3.2.5 Soundstage and Imaging
     There is enough width and depth with atmospheric tracks. Everything feels well placed. The layering and separation on offer are very good.
4 Comparisons
4.1 VSonic GR07 Classic
     The GR07 has served me well for over 2 years now. In comparison to the GR07, the FLC8S offers more sub-bass, much more mid range presence and far less splashy treble. There is more detail, naturalness and refinement with the FLC8S. Also, the soundstage of the FLC8S has more 3D feel compared to the flatter, 2D-ish feel of the GR07.
5 Conclusion
     I must admit that I highly impressed by the performance of these hybrids. For me, they score top grades in almost every department when it comes to the sound. Coming from sub $150 IEMs, I cannot really comment if the FLC8S truly delivers top-tier performance, but, I am pretty sure that its the best pair I have owned and listened to till date. Being on a student budget, it was a considerable investment for me but I must admit that I am thoroughly satisfied. For anyone looking to make the jump to next tier from the sub $150 realm, I think a pair will not disappoint.

Great review, thanks
Added a comparison with the GR07


Headphoneus Supremus
Pros: High-quality, highly-customizable sound. Small. Ergonomic. Built well. Detachable cables.
Cons: Microphonics. Overly tight cinch. Limited tip choices. Very small tuning filters.


Image courtesy of FLC



Hi guys. I discovered a real gem of an IEM in 2015, the excellent FLC8S. Out of all the IEM I tried in 2015, this is the one that most caught my attention and has gotten a disproportionate amor of ear time. How did this all come about? Well, I was chilling out, jamming to some music one day when I noticed an email in my inbox from Teo over at LMUE (Lend Me Ur Ears). In the email, Teo asked if I'd like to check out the FLC8S because he though they were a great IEM that deserved more attention. I didn't really know anything about them, so I started looking around to see what these were about. One of the first things that popped up was a stellar review of the original FLC8 by Joker over at The Headphone List (LINK). He gave them a solid recommendation, and I learned that they were the most customizeable IEM I've ever heard of. If you've followed my reviews, you might remember that I've reviewed a few customizable IEM recently. Those were the RHA T20 (LINK) and the Torque Audio t096z (LINK). I also own the Trinity Delta. While the RHA T20 and Trinity Delta offer a few different "flavors" of the same basic sound signature, the Torque Audio t096z offers six unique sound signatures. They are all very nice IEM, and I enjoy listening to them all. Anyways, back to FLC8S. They have 36, count 'em, 36 different tuning options. That sounded really cool, so I shot an email back to Teo and told him that I'd love to check them out. Well, long story short, I fell in love with them. I've shared them around a bit, and everyone I've let listen to them has also been very impressed with them. I gave them to a self-pronounced treble-head and bass-head at a local mini-meet, and both said they were amazing. I didn't even change the tuning to accommodate their preferences. I turned a couple of my fellow Head-Fi buddies onto them, and they both agree that these are right at the top of all the IEM they've listened to in 2015. Most recently, I let @Paulus XII in on them and wasn't surprised when they stole his heart, too. Yes folks, these are the real deal!
Here's what FLC would like you to know about the FLC8S:
FLC Technology is one of the earliest companies in China to explore the hybrid balance armature and dynamic driver technology. In 2011, it is the first company to launch a hybrids customs. The FLC 8S is the first universial hybrid balance armature and dynamic earphones by FLC technology. Due to FLC Technology's extensive experience in the hybrid technology, the FLC 8S features excellent cross over technology which creates a coherent sound between the dual balanced armature drivers and the dynamic drivers. 
FLC 8S recongises that there is no one size fit all sound signature for all users. Hence, it is designed to be highly tuneable so that users can tune it according to their sound preference. While tuneable earphones are not new in the market, the FLC 8S represents the pinnacle of this technology as it allows for 36 variations of sound unlike most tuneable earphones which allows only 3 different sound signature at most. 
The FLC 8S comes with improved built quality and comes with braided cables as compared to the FLC 8.
I've also had a bit of back and forth with FLC's founder Forrest Wei (@Flcforrestwei) and learned a bit about him. Like most audio engineers, you've probably never heard of Forrest. Neither had I, but let me assure you that just like the FLC8S, he's is the real deal. Before starting FLC, he worked at Ultimate Ears at the time the venerable Triple-Fi 10 were being developed. He's also worked at Jabra and Harman. As you can see, he's been around the block. He started up FLC because he not only believes in hybrid IEM technology, he believes the sound should be customizeable to give every listener the right sound signature at the right time without buying several pairs of IEM. Besides FLC8S, Forrest also sells a CIEM version with the same 36 levels of custmization. Now that's unique! FLC also has a new line of single-crystal pure silver cables with all the connector choices you need. There's also a new flagship product under development. I've heard a bit about it and can't wait to give it a listen. Let me assure you it's going to be another amazing product from FLC. So there you go. Now you know a bit about Forrest Wei. We're lucky that he recently joined us on Head-Fi, hanging out with us FLC lovers over in the FLC8S thread. Thanks, Forrest!
FLC8 & 8S Thread: LINK


There is no financial incentive from FLC for writing this review.  I am in no way affiliated with FLC, and this is my honest opinion of the FLC8S.  I would like to thank FLC for giving me a chance to test drive the FLC8S, and I hope my feedback proves useful for my fellow Head-Fi members as well as for FLC.


I'm a 43 year old father who loves music.  While I listen mostly to electronic and metal these days, I do listen to a wide variety of music - from electronic (Autechre, Boards of Canada) to modern/minimalist composition (John Cage, Philip Glass) to alternative rock (Flaming Lips, Radiohead) to jazz (John Coltrane and Miles Davis) to metal (Behemoth, King Diamond) to classic rock (Eagles, Rush).  
I'm primarily a portable audio enthusiast. My portable music journey started with the venerable Sony Cassette Walkman and then progressed to portable CD players, minidisc recorders (still have my Sharp DR7), and finally on to DAPs like the Rio Karma, iRiver IHP-1xx, iPod 5.5, iPhones, and the newer crop of DAPs from Fiio and iBasso.
Being a portable audio enthusiast, I typically listen with IEMs but am enjoying listening with full-size headphones more and more and tend to like u-shaped sound signatures, although I break out v-shaped IEM & HP from time to time for fun.
As with a lot of people my age, I've got some hearing issues.  I've got mild tinnitus and suffer from allergies, which can affect hearing in my right ear.  I'll admit it, I'm not blessed with a pair of golden ears.  That said, I've been listening to portable gear for a long time and feel confident in assessing audio gear - just wanted to be transparent up front.



  1. Driver unit: 8.6 mm dynamic drivers+ dual balanced armature 
  2. Rated Impedance: 11 Ohm 
  3. Sensitivity: 93 dB/mW 
  4. Frequency response: 20Hz - 20KHz 
  5. Plug: 3.5mm gold-plated L-plug 
  6. Cable: 1.30m TPU cable
  7. Price: $350 (LMUE)



As usual, I'll go over the packaging and accessories in pictorial format with a wrap at the end. 
Looks like a plain box, right?
Nope! The top cover folds back to reveal the FLC8S nestled in protective foam.
Then that top layer slides out to the right to reveal the carry case and accessories keychain case. Cool!
Here are all the goodies you get.
Sorry about the stray tip in the pic...
The unboxing experience is really fun. It felt like I just kept discovering more and more goodies stashed away inside. I recently got the Lotoo PAW Gold in for testing and noticed that the boxes are very similar. Turns out Forrest is a big fan of Lotoo DAPs!
I like the nearly indestructible metal accessories holder and IEM case. These will most definitely keep your FLC and accessories safe and sound for a long, long time. I'm not sure I'll ever use the 1/4" and airplane adapters. Some might, though. Honestly, these would just end up in my stash of unused accessories. I'm sure you noticed the pair of tweezers were, right? That's weird. Tweezers packed in with a pair of IEM? What's that about? Well, they're supposed to help change the tiny tuning filters. I didn't find them very helpful, though. I ended up just using my fingernails to change the filters. Maybe some will need it, but not this guy. 
The tips are basically the same shape, but the gray ones are softer and are the ones I preferred. And surprise, surprise, tip rolling has been a topic of discussion on the FLC thread. While I enjoy the sound with the stock gray tips, some don't like them and end up using third-party tips. Wide-bore double-flange seem popular. During my conversation with Forrest, I learned that the stock tips were chosen because they conveyed more detail. Even so, it'd be nice to see some different tip styles included to accommodate differences in ear anatomy and to allow users to further refine the sound to their taste.
NOTE: The tuning filters are really small, so make sure to change them over something that can catch them if they fall.


Again, I'll attack this section in pictorial format, commenting on what I like and what I think could be improved as I go.
You can see a lot of the elements of the FLC8S in the picture up above. Lets start off with the earpieces. You can see all three types of modular tuning components for each earpiece that make the FLC8S so unique. On the left earpiece's inner face you can see the RED ULF (Ultra Low Frequency) tuning filter, while on the right earpiece's outer face you can see the GRAY LF (Low Frequency) tuning filter. You can also see the GUNMETAL MF (Mid Frequency) + HF (High Frequency) tuning nozzle. All of these are easy to remove. The tuning nozzles simply screw in. ULF and LF tuning filters are friction fit and fit in snugly. The ULF tuning filter is hard plastic and is the smallest of the tuning components. The LF tuning filter is made of silicone and is a bit bigger. It's easy to distinguish between these two, so you're not going to be putting the wrong tuning filter in the wrong port. Since they are quite small, please change these over the carry case or something similar so you don't lose them. FLC includes an extra of each ULF and F filter just in case you do lose one, though. And if you're really worried about losing them, you can purchase the tuning accessories keychain kit separately.
You can also see the braided detachable cables with memory wire. All is color coordinated in a tasteful BLUE. Perhaps you can also tell from the picture that the FLC8S is pretty small. If not, I'll include an in-ear picture below to show you that they are indeed pretty darn small.
FLC8S Schematic
Here you can see all the tuning components, as well as the internals. I'll go over specifics for the different tuning choices available in the next section, but this gives you an idea of how flexible the FLC8S are in finding just the right sound for you.
Cinch, Y-Splitter, L-Plug
Good news, bad news time, people.
Stock Cable
Bad News: The stock cable is fairly springy and is microphonic, and the heat shrink tubing looks a bit shabby. Moreover, the cinch shrink tubing is so tight I had a very hard time moving it up the cable.  I let Forrest know this. He relayed this to the team, and they've made the cinch made a bit looser.
Good news: The FLC8S comes with a high-quality OFC braided copper cable. With its coordinating blue color and heat shrink tubing, it has quite the boutique appearance. And I really like that it has an L-Plug that works with smartphone cases. 
Original Cable
Besides the stock cable, there's also the original FLC8 cable which is a standard black copper cable that is more supple and comes with a more typical, functional cinch and lacks memory wire. The copper is a bit lower quality, but it is a highly-ergonomic cable and allows the user to choose between wearing the FLC8S up or down and is lees prone to microphonics.
Silver Cable
The newest addition to the FLC lineup is the brand spanking new single-crystal pure-silver cable, which is very similar in construction so expect the same springiness and microphonics. I just got this, and the cinch on it is just right. Nice!
FLC Cables: Original (top), Stock (bottom left), Silver (bottom right)
NOTE: FLC8S use the same 2-Pin connector as the venerable UE TF10, so you'll have lots of aftermarket options should you choose to go that route.
In addition to the regular blue color, FLC8S are also available in a Limited Edition Red model. I think a mix n match model would be awesome!
Worn Up
Here they are worn up with the original FLC8 cable that doesn't have memory wire. Very comfortable for my ears.
Worn Down
With the original FLC8 cable, you can wear them down since it lacks memory wire. This isn't as comfortable for my ears, but my ears are a bit on the small side. I suspect those with anger ears will find it more comfortable. in any case, it's nice to have options, and I do find myself 
Those of you who know me know I listen to a lot of electronic and metal. You might even know that I've been jamming a lot of classic rock lately, as well. I typically listen to music from Autechre, Behemoth, Bjork, Candlemass, Depeche Mode, The Eagles, Fleetwood Mac, Iron Maiden, King Diamond, New Order, Rush, and Sigur Ros during my time with new gear. I might throw in some hard bop jazz or modern minimalist composition every now and then. Just wanted to make sure you know what kind of music I listen to for context. Unlike some other reviewers, I don't keep to a strict playlist. Instead, I choose songs I know well and feel like listening to. I feel it's more organic that way. Anyways, on with the show, eh...
As mentioned above, FLC8S has a lot of tuning options. So as opposed to trying to impress you more with vivd descriptions of their amazing sound, I'm going to discuss the various tuning options and which I prefer. Let's start with a run-down of the various tuning filters.
Ultra Low Frequency
  1. Clear = Minimum
  2. Gray = Medium
  3. Red = Maximum
Low Frequency
  1. Clear = Minimum
  2. Gray = Medium
  3. Black = Maximum
Mid + High Frequency
  1. Blue = Medium Mid Frequency + Low High Frequency
  2. Gunmetal = Medium Mid Frequency + Medium High Frequency
  3. Gold = Maximum Mid Frequency + Medium High Frequency
  4. Green = Medium Mid Frequency + Maximum High Frequency
Ok, now you've seen all the tuning choices that await you. Perhaps you can guess what some of the trends are. Did you guess that most people prefer the GRAY and RED ULF tuning plugs? Yup! Perhaps they also prefer the GRAY and BLACK LF tuning plugs? Right again! You also think most people like the GUNMETAL and GOLD MF + HF tuning nozzles? Man, you're good! You got them all right!!!
I played around with the various tuning plugs and nozzles and rapidly came to the conclusion that I'm not a fan of using the clear tuning plugs at all. They gut the bass. Not a fan of the blue tuning nozzle. Guts the upper end. Green's not my favorite, either. It's ok, but it's got a bit too much upper end energy for me for general listening purposes. After nailing down which tuning plugs and filters I'd rather avoid, I started working with my preferred tuning accessories to hone in on my favorite combinations. 
My hands-down favorite is RED-GRAY-GOLD Well-extended bass with good bass impact. Mid-bass is very well balanced with sub-bass. upper bass is reigned in. Very nice. Not boomy. Mids are tilted a bit towards the upper mids. The upper end conveys a good amount of detail without veering into harsh territory. I'd highly recommend using that as a starting point and then try substuting one of the tuning plugs at a time to hone in on your favorite. 
Some of my other favorite tunings are:
  1. RED-GRAY-GUNMETAL. This is very similar to the RED-GRAY-GOLD combo up above but the upper mids are a bit more relaxed. A nice warm, relaxed listen.
  2. GRAY-GRAY-GUNMETAL. This is the default combination and works very well as a reference tuning.
  3. RED-BLACK-GOLD. Choose this when it's party time and let the bass kick!
Beyond the basic tuning, FLC8S is able to convey a good sense of space and spacial cues. It's not the best I've heard, but it is above average for it's price and competitive with higher priced IEM. Of course some of this is source dependent, and I've found FLC8S scales well with increasingly better sources. I've tested it out with my iPhone 5s, Aune M2, Cayin N5, iBasso, Shanling M2 & M3, Soundaware Esther Analog, and most recently the Lotoo PAW Gold. While the FLC8S sound just fine out of my iPhone, add a decent amp to your audio chain or plug them into an entry level DAP and you notice the dynamics are a bit better and the soundstage increases. Move up to a mid-level DAP, and again the FLC8S doesnt at all feel like it's holding your audio chain back. Hell, I'm listening to them out of the PAW Gold I just got in for testing, and it sounds amazing! It's with PAW Gold that I can really hear FLC8S performing at its highest level, and the benefits of the new silver cable are most evident. So if you get the FLC8S, just know that it'll keep up with you as you upgrade your audio chain.
I've skimmed some of the other reviews. While I consider the ability to alter the tuning a major strength of the FLC8S, I noticed that a couple people seemed to feel it was a gimmick. Obviously, I disagree. Let me be completely realistic about this. I don't expect anyone is going to be out on the bus and think to themselves, "Hey, I want to change filters on my FLC8S right now." That's pretty unrealistic. However, every once in awhile I do like to change the filters. Like I pointed out above, FLC8S can be a reference-tuned IEM if you configure it properly. So if you need that, it's there for you. Want to throw on some bass-laden hip-hop or electronic music and just give in and have some party time fun? Yup, you can do that, too. Feel like a v-shaped sound sig? FLC8S has you covered. you can even get a dark, warm sound signature if you throw on the BLUE tuning nozzle. Of course, you'll probably go right back to your favorite tuning afterwards. So what? At least you didn't have to go out and buy another IEM to get a taste of those other sound signatures. FLC8S has you covered, baby!


By now, I certainly hope you're intrigued by these. I truly feel that FLC8S are an undiscovered gem in the IEM universe and hope they finally start to get the attention they deserve. Make no doubt, these are a phenomenal IEM with great sound in a nice, comfortable, small package. Add the ability to tune them to your liking, and they're a force to be reckoned with. And in my opinion, Forrest did a great job creating a highly-tunable IEM. Are they perfect? No. Are any IEM perfect? Of course not, and don't let anyone try to convince you otherwise!
So what could be better? Well, I mentioned a few minor nitpicks along the way like microphonics, the overly tight cable cinch, and limited tip selection. Luckily the FLC8S have detachable cables, so if you end up falling in love with them you can always look around for a cable that fits your individual needs. There, that problem's solved. Tips? Well, who amongst us doesn't have way too many tips floating around? I mean honestly, I've got more tips than I know what to do with! So that's not really a big deal, either. The one thing that can't be changed is the very small tuning accessories. I know a lot of prospective FLC owners will be nervous about using them. Luckily you can purchase replacements, so just order a set of replacements when you order the FLC8S and you'll be set!
To wrap, I'd like to congratulate Forrest at FLC for crafting a superb IEM that is competitive with IEM that cost significantly more. I look forward to your future creations with great anticipation!
Btw great review...kudos...enjoyed reading about Forest's background, too. Wish we'd get more bio stuff from the smaller new companies...adds both a bit of charm and respect for the skillsets they're bringing to the table.
I'm so intrigued by these...thanks for the review. You can obviously write a really (REALLY) long review, but you were concise and very readable... Thx!!
Thanks for review.
Which one would be better?
Dudu 2002 or FLC8s


Headphoneus Supremus
Pros: balanced and rich sound filters are great. Choice of at least 2-3 major sound sigs with variations
Cons: Relatively expensive, cable ergo/noise, no mic or remote. cust-ty ultimately redundant. M-by comfort and fit due to the design, bit bright highs
First of I'd like to thank DJScope and FLC for organizing (part of the Australian FLC 8s tour). I got to enjoy FLC 8S over the holiday break and try them with a variety of gear




Accessories - good. no foam tips or shirt clip though. bit of a pity there. Really like the Metal case. Rather great packaging and useful user guide as well. Didn't really like the plastic tweezers that were much too long for using them on the go and not really grippy (used for swapping the silicon bass port )
Build - good. overall I get a solid feel from the RA plug, IEMs and nozzles/ etc.
Comfort/Isolation (hmeh): keeps falling out of my ears with foam tips of different sizes, mostly because of the shape of the body and L shaped plug. There's also a wind noise issue for relatively significant wind (mostly noticeable when cycling or if there's strong wind). FLC mention there's a pressure EQ vent set meaning you the 'vacuum against the inner ear' type pressure, but that's not really uncommon for hybrids afaik, at least the ones with vents. We'd probably get a better fit/comfort and isolation from a different body design , although I'm not sure how much the design is dictated by allowing the customization port spaces.
The biggest highlight is probably the 3x ULF (plastic 'pins' for sub-bass ports), 3 LF (3 silicon cylinders for bass ports), 4 nozzle filters ( for HF+Mids tuning) . While IMO the number of usable configs is about 8-10 it's still a lot more flexible than AKG k3003 or AX60 where you swap the mids/highs filter (well, one filter but I think it did affect bass venting there too)
Cable (blah-hmeh) : memory wire not as good as on UM westone cables. Cable noise. Slightly dodgy plastic y-split and chin slider. There's also no Android or iPhone remote. These days, for above $300 I'd really hope to see a 1 if not a 3 button one. (T-PEOS can do it, Fidue can do it, so can the rest of the hybrid manufacturers)


X2 v7.0e firmware (greatest dynamics, firmest bass and not much sibilance) - on neutral EQ [I'm hugely impressed with X2 + FLC8s) > Note3/Clip+ latest rockbox (bit of sibilance, bit softer bass and dynamics) > X3 v1.1 (fuzzy all around a bit)

Sound options/Overall.

You could definitely get any of the following sound signatures: Balanced , bass light, vocal forward and treble happy. or combinations of thereof. Personally I would exclude the following filters from the combinations:
Clear LF (not enough bass), Clear ULF (not enough sub-bass), Green Nozzle (most HF. Treble razors of death), Blue Nozzle (highs dimming filter and I'm fairly sure also cutting a bit of upper mids). I'd personally also exclude the Black LF silicon filter ( a bit of bass bleed into mids from it affecting clarity).
That more or less excludes the bright and too bass light versions and leaves: (I think , if I make up some stats, 90% of the people using these will go for the two tunings below)
a) Balanced with variations on sub-bass (I don't really feel much difference between the gray and red ULF filters) - filter being ULF:Red or gray, LF: grey LF, gunmetal blue HF filter. This is overall enhanced sub-bass, neutral but full bass, and somewhat linear mids and treble. Treble is still sparkly and a bit bright to my liking but will be ok for most people. Mids are a bit recessed for my preferences e.g. ok for the Queen, but not so much for classical (I prefer the mids to be more forward for classical) but YMMV. Clarity across the range is good. I get a bit of sibilance in about 15% of my library e.g. some metal, pop, etc. All in all I think about 50% of the people around will like this tuning a lot.
b) Enhanced sub-bass, somewhat enhanced mids and mostly linear treble (same as balanced but enhanced mids) - Red ULF, Grey LF and Gold HF/Mids filters. That's my favorite tuning / matches my sound preference . There's still a bit of sibilance with a bit of metal, pop etc as with the balanced tuning , but I can listen to these unEQed. The sub-bass impact, and bass to mids balance is very very impressive, as are sub-bass/bass/mids clarity.
For bass-head levels of bass and no sibilance I do +3db @50hz, q=1.6; -0.6db @ 160hz, q=1.5; +0.8db @ 800hz, q=1.6; db=1.2 @ 1250hz, q=0.8; -0.8db @ 7khz q=1.5; -2.2db @ 8.35khz, q=0.7; -1db @ 9500hz .


these are probably as impressive as T-PEOS H300/A-350 (more balanced than these), and Dunu DN2kj (Dunu has deeper bass and is more treble hot/happy and sibilant). And more so than AX60 (that I don't really like) and Fidue A83/73
That said I can't help but question the value proposition given the price and suspect comfort. I think FLC might be better off making a balanced and enhanced everything IEM with better comfort and less options at a better price and perhaps better comfort. As it is, I'd gladly buy it at 250 but not 350 USD, and to me it feels a bit like a transformer toy - cool but will you really play with just your favorite config 99% of the time (given it's cumbersome to change filters on the go and I can't really think of a compelling reason to deviate from the two chosen filter configs above) . I'm still sure these will have more than a few fans in the relatively affordable hybrids to buy option list.

Bye now, thanks for reading.

ps the final head-fiish rating is:
audio q: 4.5
comfort: 3.5
design: 4
isolation: 3.5
value: 3.75
i agree...while i haven't heard these, i do like the flexibility: but the constant choices of filters is too cumbersome.
instead of filters, give me a few screws on the side to tweak the bass  (like the aurisonics asg 2.5 or the senn ie 80)
and make it easier.


100+ Head-Fier
Pros: amazing packaging, good sound
Cons: not as versatile as advertised
FLC 8: going for the long haul
I received these in December as part of the Australian tour and only have had a little over a week with these, so there might be some reason to take these impressions with somewhat of a grain of salt.
A little about me
Personally, I am a person who tends to gravitate to high end equipment, but have recently started looking at the low-mid end segments of the IEM world, since I have come to the conclusion that I have had my head stuck up in the clouds for too long. While I love trying new equipment, the equipment I end up buying tends to be little. This might be due to my lack of a decent income, or because I have very high standards, honestly I am not sure. However, one thing I am very sure of, since I have a rather limited budget, whatever I tend to buy or recommend are things I love, instead of hyping the regular item. While I believe sound quality to be extremely important, I also highly value ergonomics, and love things that look beautiful as well.
I tend to use my earphones when I’m out and about, so I am mobile with my portable setups. This must be stated because this means that I am often walking around while I use my IEMs and as such, ergonomics is quite an important consideration for me.
I have previously stated that I have had problems with IEMs that stick out of the ears due to size, or any number of other factors that are often presented by the IEM makers. An example of this is the Fitear series, which I have a serious love hate relationship with, due to the way the IEMs always stick out of my ears, and consequently fall out after a short walk. This causes me to stop and push them back in every few minutes, which eventually made me sell them (I rarely sell my gear, so this was definitely a huge issue).
FLC did not give me such huge problems with the 8. Let’s go over what I thought in detail here.
Overall, the shape of the earphone is designed to be fairly ergonomic. One feature I particularly liked was the shape of the IEM, which was designed in the vein of the popular westone/shure shape, but definitely quite different. This might be due to FLC wanting to be iconic, tuning, or even legal liability, I honestly have no idea. This shape, in theory at least, is particularly good for people who are often out and about, since the user is forced to use the IEM over the ear, while also not overly shortening the cable when using it in this manner (honestly, I’ve only had an issue with this with the customart demo tour, but once bitten, twice shy and no I don’t have a very big head).  Sadly this is hampered by the way the wire is connected to the IEM. Being a removable cable IEM with an L shape connector, the area where the cable is plugged into the IEM is slightly at the wrong angle for me. This causes great irritation to me because the IEM does not sit flush to the ear and kind of just bounces around when I walk. This obviously might be a problem that only I have, since many people were wondering what I meant when I first posted about this issue in the FLC 8 impressions thread (as such, this part might be taken with a pinch of salt I guess). Personally, I have never had this issue, despite having several custom IEMs which all use L shape connectors (I prefer this connector in general honestly).
It has to be said though, that the IEM is really built with love. The custom blue cable, instead of a generic black one, is a welcome sign, featuring a beautiful chin slider and an overmolded L 3.5mm plug. The fact that this is not a generic cable honestly needs mentioning, because a significant portion of the cables that the portable audio industry provides with their IEMs when the cables are removable are utter generic trash that seem to come from the same company, and tend to break very easily. The memory wire on this IEM is also there, but that is more of a personal preference thing, with me not liking memory wire in general.
Another issue that needs to be mentioned is that the little modifiers on the IEM are actually very small indeed, and since I am a total klutz, dropping and losing them is a legit issue. However, if the modifiers were larger, I think it would defeat the purpose and appeal of the IEM, so I would urge caution when changing the modifiers on this IEM.
In conclusion, let’s call it a good attempt.
I honestly am not too sure about how I am supposed to do this portion since I actually was able to hear different kinds of sound signatures when I switched out parts. Technology that enables modification on the IEM for variability in tuning has come a long way from the ****ty Hippo VB that I had many years ago, which really didn’t change very much with the “bass modifiers” (Pfft….Rip-off).
Anyways let’s get on with some overall impressions I guess.
 The treble on this is not something that stands out for this IEM. Even with the appropriate modifications, the IEM did not become sibilant to me, a big plus in my book.
The mids on this IEM were pretty good indeed, with the gold nozzle attached, vocals became more detailed and had some air to them. While the gold nozzle was amazing for midrange, I didn’t get the sense that the mids were lacking on this IEM with any of the combinations, yet another plus in my book.
The bass in my opinion is where the biggest change occurs. While it isn’t like what I heard in the Layla, there definitely is quite an ability to change. However, the way that the bass did not bleed into too much of the remainder of the music spectrum was definitely something that was quite Layla-like indeed. This is quite an amazing feat, since the Layla is a stratospheric level IEM in terms of cost, and costs as much as several FLC 8s.
The soundstage on this is decent, but not overly exaggerated. The imaging on this is also pretty accurate, and nothing really stands out to me.
I tried this IEM with several sources, namely the iPhone 6+, the Calyx M, the Resonessence Labs Concero HP and the Cozoy Aegis (with computer and iPhone). While the others presented differently in terms of detail levels and amplification levels, I personally felt that the Cozoy Aegis produced some magical sound with it. I was dumbfounded when I first heard the combo, and it was not surpassed by any of my other sources. Synergy matters guys!
I am a person who likes variation in my music; I personally feel that changing the modifiers out in the field is an unrealistic feat for many. As such, the FLC 8 quickly lost its appeal in that manner. I personally ended up just leaving the IEM in just 1 general setting and not changing it depending on my music needs.
Balance and pairing
From the above paragraphs, it can be seen that I am not able to write many impressions. This is actually because I am not really able to criticise this IEM very much, since nothing really stands out but nothing really sucks either.
I personally ended up using the black/black/black (not too sure about this) the most, since I ended up liking it the most.
The packaging on this is actually something amazing and is definitely built into the money that you pay for the IEM. The amount of stuff that you get when you purchase this IEM and the packaging certainly puts many competitors to shame. I shall now list the items.
8 pairs of silicone tips (soft tips, does not need aftermarket tips for additional comfort)
1 metal case (wow, gives it a high end feel)
1 pair of tweezers (large and not portable, which leads me to the question of why did they make the modifications so easy to carry around?)
Modifications in a catheter (good case to keep the modifications, I am assuming that it was made this way to be brought out into the field easily)
Accessories box
It must also be said that the box that it came in was impressive, unlike the usual cheapness that we usually get as audiophiles.
This IEM looked amazing in my opinion. Sadly I was not able to fully utilise the time I had the IEM to produce any nice images, since I totally miscalculated the number of days I had it for and had no choice but to try to take photographs at 4am, on the day I had to send it off. It seems I vastly overestimated my ability to do things while severely sleepy, which resulted in me coming up with some pretty horrendous pictures. It must be said though, that the IEM has a high end look that is a breath of fresh air in the portable audiophile world. Adding the accessories into the mix makes this a very potent package indeed. I mean, how nice is it to have a nice metal case instead of the usual soft foamy things that come with most IEMs?
Let’s face it; the FLC 8 is a ridiculous item. 36 different types of sound signatures in 1 IEM… ARE YOU KIDDING ME? The honest truth is that I think that the FLC technology flc8 is a feat of technology. While it probably isn't my type of thing, I believe that FLC technology really put in their heart and soul into making this IEM and it shows, with the technology and the amount of effort that they put into it aesthetically.
I also think that I am of the minority in Head FI who doesn't like to have too much gear (BLASPHEMY!). This IEM has the potential to appeal to many with its versatility, and it is hard to argue with the versatility, and as such the value, in theory, but I found it hard to implement in my daily life, your mileage may vary. While I would have no qualms recommending this IEM to anyone out there, I would definitely recommend trying it before buying, due to the fit issues I had. 
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Thanks for joining the tour, mate! Cheers!
Thanks for your review, which one is better choice? DUNU 2002 or FLC8s?


Headphoneus Supremus
Pros: Everything -- no exaggeration. Visceral sub-bass. Ruler-flat "stock" FR. Metric tonnes of microdetail. Huge stage. AFFORDABLE. Truly customizable.
Cons: Uh... hmm... well..... The cable is not the single greatest pinnacle of cable technology ever? I guess...
This IEM is a complete game changer. Prepare to be upset by your recent $500+ purchase, or thrilled that you held out for something truly worthwhile. You don't know who FLC Technology is -- good. The surprise is worth it. Just buy it. Don't wait for me to write a more complete review. I might, but I'll probably be too busy listening to these IEMs. Check out the wise words written by other reviewers on this page. Do it. Buy them. You are being peer pressured. Submit.


100+ Head-Fier
Pros: Sound, Versatility
Cons: Memory wire makes fitting harder
Product link: http://www.lendmeurears.com/flc-8s/ (apparently currently out of stock)
So... This is my first time writing a review after lurking in the depths of Head-fi for three years, so bear with me

A bit about myself - I'm a female student from HK studying in the US. I mainly listen to classical, instrumental and pop, and in general I tend to enjoy headphones that are balanced with a touch of warmth. I also value a wide soundstage, accurate positioning, and to a slightly lesser degree clarity and micro-detail retrieval. I should also mention that I'm not very tolerant towards sibilance and shrill treble in general. As a student I can't really get expensive gear all the time, so the FLC8S are my second pair of top-tier IEMs. I got these during the "Double 11" Chinese holiday discount, when these were priced at USD $250. These have over 50 hours of burn-in, most likely 100 hours, on them. 
The FLC8S, from FLC Technology, is a dual BA/single dynamic hybrid released this year. Its biggest selling point was the 36 different sound signatures that you could switch between by way of nozzles and filters. It's been reviewed by ljokerl in his huge IEM thread, but they haven't received much attention around here, even though I feel like they're one of the best universal IEMs I've ever listened to. As such, I've decided to write a review on these, so that more head-fiers can get to know and appreciate this pair of amazing IEMs. 
Setup used: 
Portable: LG G4 --> Dragonfly 1.0
Desktop: MacBook Air --> Objective2 Combo
Appearance, Build Quality and Fit 
I don't have the packaging with me right now, so sadly I don't have pictures of the box. It did come very nicely packaged with a three-layer intricate box. There was a little plastic bag of tips in 4 sizes (XS, S, M, L) with the clear M tips on the headphones. Other accessories include a pair of tweezers (which are actually not very useful), a screw-on metal hard case that seemed very sturdy, an airplane adapter, cleaning tool, and - most importantly - the keychain with all the filers and nozzles.
The FLC8S are not black as suggested by a lot of pictures online; instead, they are slightly blue in color.The IEMs themselves are surprisingly small. Even though they look plasticky, they seem well-made. Another bonus is the removable cables (I have not tried pulling them out yet - a brave soul who gets these headphones can try!). The cable's braided and seems pretty sturdy, even though the upper part seems a bit thin. It's slightly bouncy and microphonic, but I don't find it a major problem for me. One thing I'd like to mention is the memory wire portion, which created some troubles for me initially - I've been spoiled by the nice cables on the Westone 4 and thus found the memory wire pesky, as it prevented me from getting a secure over-the-ear fit and the headphones would move easily when I was walking. Eventually, though, I got used to it. Another problem is the non-angled nozzles, which may be a problem for some people. I personally found it fine but my friend did complain that it was slightly uncomfortable when he put them on, so that's also something to consider. Besides these two minor points, though, the fit is very nice, due to the small form factor. They're also very light, which helps a lot in securing the headphones. 
A major selling point is the tunability of these headphones - the nozzles are interchangeable, and there are two bass/sub-bass ports on the housing. It's surprisingly simple to switch, although I do recommend working on a clean surface - I've already nearly lost a few parts during the switching. Switching does require a (fairly) steady hand, but it's not a big issue - I believe most people won't have problems. The filter/port/nozzle container (whatever you want to call it) is tiny and the organization isn't exactly very elegant, but it gets the job done in a compact way. The container's also pretty portable and fits into the metal case. Overall, I'm surprised at the build quality of this - its tiny form factor and sturdy housing is pretty nice. *inserts gif of an excited child opening a package* 
Some pictures of the FLC8S ft. Macbook Air - sorry if they're not of very good quality: 
There is a slightly metallic, bluish tint to the headphones. 
The sub-bass port is on the inner surface of the housing (the red dot - high sub-bass port). From the top you can see the golden nozzles I'm currently using.
The memory wire (top part) isn't exactly the most user-friendly, but the braided cables are rather thin and light (and sometimes bouncy). 
The tuning container/keychain with all the nozzles and filters I'm not using. The container isn't very elegant but it fits everything in a small space.
The dark grey dot on the housing is the bass tuning port (set to mid). The nozzles aren't angled, which may be a problem for some people.
Sound Quality
Since there are 36 possible sound tunings I'm not going to talk about all of them. After some experimenting, though, I've found a few pairings that I liked a lot. I'll briefly talk about those, as well as the overall sonic character of these gems. 
It's hard to discuss these without first talking about the tuning. So apparently there are 4 nozzles which influence the mids and the highs, 3 bass tuning filters, and 3 sub-bass tuning filers. I think everyone's going to stop reading this (and pass up on these things... 
) if I discuss all these nozzles in detail, so I'll just stop obsessing over them now. I did give all of the combinations a try and eventually settled on a few that I found was wonderful for the genres of music I listen to. 

Pairing 1: Red (High sub-bass) - Grey (med bass) - Gold (high mids/med treble) 
Pairing 2: Red (High sub-bass) - Grey/Black (med bass/high bass) - Black (med mids(?!)/mid treble)
Pairing 3: Black (Med sub-bass) - Grey (med bass) - Green (med mids/high treble)
First Impressions: 
Geez, these things are good. Straight out of the box they sounded so smooth and clear at the same time already. The soundstage was spacious, vocals were airy, bass was there but not too much... Compared to the Westone 4s these sound very, very clear. The detail is really nice - I could hear the smallest breath noise from EXID - and vocals seem very natural. Treble seemed slightly brighter than what I'd gotten used to on the Westone 4, but in a good way. It was clearer, a bit more shimmery but not to the point of being sibilant or intolerable. Seems like we've got something glorious in the making here....
As I've said, I'm pretty sensitive to sibilance. By all accounts this isn't a pair of super bright headphones, even though with the green or blue nozzle you could make it border on burning your ears out. With the less treble-happy tunings, however, the treble is very clear and effortless - it's just there. Even when I used the green nozzles, with the right tuning I could tolerate the slight sibilance of the pop tracks. In orchestral music, especially, the treble is bright, but not overly so - just enough that you can maintain an excellent balance between detail and smoothness. Cymbal clashes sound very lively and energetic, with just the right amount of sparkle. It's a pretty good balance. With the more treble-happy nozzles, there's more detail (and sibilance), but with the right tuning and right tracks it can make the orchestral pieces sound incredibly detailed. The airiness also makes the treble extremely natural - and this isn't just limited to the green nozzles, it's the same for the gold and black nozzles.
Warning: with the wrong tuning using the green nozzles these can be extremely sibilant. You have been warned. 
I enjoy the mids immensely on the FLC8S, especially with the gold nozzle. Vocals seem very airy and detailed; the mezzo-soprano's voice was captured perfectly - it feels like I'm listening to a live opera performance. There's probably no way to screw the mids up on this thing - they are that good. Nuff said on them.
Ah, the magical red filter. 
Orchestral music just comes to life here - the bass isn't exactly linear like reference flat headphones (Brainwavz B2, looking at you) - slightly more exciting than that. It adds another dimension to the music, there's the constant presence of the cellos and double basses; yet they don't overwhelm the piece - they're just there, like everything else. The sub-bass extends pretty low, with a nice rumble and I don't really notice any mid-bass hump - probably because I'm using the mid bass ports - and so the bass is very strictly controlled the whole way. It's also pretty quick - EDM lovers will probably be satisfied with how the bass handle your music. I'm really happy with how these handle the bass region - they're so in control, so authoritative when I give it my attention, yet unassuming when I need it to be. Probably my favorite part of the whole spectrum.
Across the spectrum and other notes:
These are incredibly coherent - @Flcforrestwei has done a really good job doing the crossover of drivers. It's hard to characterize them by a single sonic signature, but in general I'd say they are rather balanced, and slightly skewed towards either the cold side (with the green nozzles) or warm side (higher bass). There's no noticeable hump in any region as far as I'm concerned, and they are rather spacious no matter what you do to them. The soundstage is very wide, with pretty accurate positioning, and there is no veil even if you crank the bass up. They also don't have that artificial timbre that I sometimes get from other headphones (especially some IEMs with metal housing) - everything sounds very natural, and I noticed that especially with the mids, they just seem so effortlessly smooth yet detailed. It's a wonderful feeling.
I feel like the difference between the nozzles/ports are very noticeable and they really do a lot to change the sound, but ultimately the whole sound signature is still built on airiness, detail retrieval and great control - and no tuning can change that. Which is a good thing. 

My favorite pairings... 
Combo 1: Red - Grey - Gold 
This is what I use for a lot of vocal-focused songs. I feel like it gives me enough bass rumble and excitement to pump up the piece, yet it doesn't overpower the vocals. With the gold nozzles, vocals are prominent, smooth and airy - very very realistic, as if I'm watching a live performance. I feel like the "magical red filter" just helps improve everything - bass presence, warmth, balance, etc. Using the black filter kind of takes away from the whole excitement. 
Combo 2: Red - Grey/Black - Black
Grey's a more neutral choice, and black's a bass cannon (well, not really, but on the scale of FLC8S...) 
I usually listen to pop songs with this combo, mainly because it's the most versatile and balanced across all spectrums. It doesn't provide any emphasis on any region and everything is smooth across the spectrum - no humps, no peaks - and even pieces that aren't mastered that well sound fairly musical. Again, the red filter does its magical job again by up-ing the oomph - the thumping when listening to dance pop music is incredible. When I use the black ports instead of the grey ones, the FLC8S instantly becomes a more bass-heavy headphone, akin to the Westones in quantity, but exhibiting more control in my opinion. 
And you know what the best part is? It still doesn't overpower the other parts of the spectrum. 
Combo 3: Black - Grey - Green
Pretty bright combo - I thought it wasn't my thing. I was wrong. 
Listen to a vocal piece with this and the green nozzle absolutely nails the high notes. Listen to an orchestral piece (and maybe using the "magical red filter") and hear the violins come to life, performing right in front of you. Although I'm usually not a fan of bright treble I absolutely love this combo for classical music - somehow the treble manages to be airy, detailed, with slight sibilance but tolerable by my standards. It gives me so much more detail to look for during orchestral pieces - the attack, the cymbals crashing, the balance... I'm amazed at what these little IEMs can pull off. It's bound to be something a treblehead will enjoy, listening to all the detail in there. 
Even though they are really, really easy to drive - already sounds pretty well straight out of G4 and a bit of improvement with the Dragonfly - they scale up pretty well. On my desktop setup, using the O2 enables me to hear even more detail on the same piece, and everything is just tightened up a tad bit more. Not a huge improvement, but definitely noticeable. 
I think airy and detailed seems to be the common theme between all the different sound signatures here - I feel like the FLC8S are an incredibly versatile pair of IEMs with its foundation built on the two qualities that I cherish most. For me, these are end-game IEMs - it does everything so well that I don't find myself reaching for other pairs of IEMs in my collection when I'm using these. Everything combined, the FLC8S are an amazing package despite the tiny, tiny problems in terms of design - I couldn't have asked for more in any pair of IEMs, albeit this pair priced at a mere $250 (or $310). Considering their asking price, I feel like these should receive more attention - even if they only had one sound signature - and everyone should have the opportunity to experience what they pack in such a tiny form factor. 
Thanks for the review, really interesting hybrid earphones 
I am pleased also FLC 8s.
Great review :) i hope to get a chance to listen to them one day


100+ Head-Fier
Pros: The sound. THE SOUND !!!!!!!! Hi-Res without the sticker
Cons: cable can be improved, easy to lose tuning parts, isolation is good not great
First of all I only had like one week to try the IEM and finish this review so take it with a grain of salt.
I also didn’t have time to take photos so I’m really sorry that this is just a pure text review :frowning2:
Have you heard of the FLC8S ? No ?
What about the company that made it, FLC Technology ? No ?
Well neither had I before DJScope asked me to join the Australian tour of it.
Just to clear things up, I’m not associated with FLC technologies in any way. The review unit was sent to me by Djscope and I am not sponsored or endorsed by anyone in any way.
I’ve always seen the IEM on the Singapore based Lend Me Ur Ears online shop, but I have always dismissed it. I didn’t even look at it for more than 1 minute as I thought it was much overpriced for an ugly earphone made by an unfamiliar company. Even more, the tuning system of interchangeable nozzle and two of its plugs made it seem complicated and gimmicky. 
Boy have I never been more wrong.
Let’s start with the fit and finish.
The 8S is pretty much all dark blue in colour, all the way from the jack, to the ear tips, the body may seem black but under proper lighting it is actually a very dark blue finish. The cable is braided and is held together by a very plain and simple plastic sleeve for the Y-split. The same plastic is used for the chin slider and this is where I would take a point off the build quality. To me, this plastic sleeve is simply inadequate and may not last for very long.
The cable on the earphone is quite soft but is a bit springy but nowhere as springy as that of the FiiO EX1. I quite like the cable’s look and feel to be honest but I do notice that the cable does cause quite a bit of microphonics. So far, I’ve mostly used the IEM when I’m sitting with my laptop so I’m not so sure how it will handle when used while walking.
The cable is connected to the body by a 2-pin connector that holds on securely but will not be a struggle to remove. The connection is flush with the body making it appear as a part of the body itself. Just from the looks I didn’t even know that the cables were removable.
The actual IEM housing is very well built, the plastic quality and the finish is on par with the big brands such as shure / westone. It's solid, smooth and doesn't get easily scratched.
It is definitely superior than low grade chinese IEMs such as RE-400 / VSD series by Vsonic and etc. 
The quality of the accessories is… fairly good. The interchangeable nozzle seems very durable but the low frequency plugs are very small in size. Not that I’m afraid of breaking the plugs but I can see people losing them. It’s a nice gesture that they include spares but it is still a bit of an issue. Plus, due to the small size it makes changing the plugs almost impossible without a clean, still surface.
The sound quality of this IEM is simply superb, but due to time constraints as I only have one week to listen and write a review for it, I cannot describe each any every tuning characteristic in too much detail.
In general I’m utterly impressed with this IEM. I strongly encourage those who have yet to try to give the FLC 8S a chance.
For the highs, the fitting of the interchangeable filters should be carefully chosen to match the type of music prior to listening for the best experience. The difference in presentation of the filters is quite significant and when an incorrect filter is used, certain music genres can sound undesirable. The use of green filter for example would be far too bright for pop / rock songs, making them sound splashy and sibilant, but when used for classical songs can make them sound extremely detailed spacious and airy. The opposite is true when using the reduced high frequency blue filter, it makes energetic songs with lots of hi-hats and cymbal hits sound easier to listen to but makes classical and vocal-centric music sound a tad dark and lacking in air.
Included in the package are 2 more filters, the gold (mid centric, normal highs) and the black (normal mids, normal highs). I find that the black (default/neutral) filter is the most versatile in that it can be used for most music genres.
Extra notes: the highs presented by the IEM is also variable depending on the ear-tip of choice. I find that using the JVC spiral dot tips made the highs more prominent making it a bit too bright/ harsh for me. So far I find that using the TX-400 Comply tips gave me the most ideal presentation.
The mid-range is absolutely fantastic on all of the settings. Just be wary that the tuned down HF filter can affect the upper vocal region slightly making female vocals sound a tad darker/ nasal. The mids in general is crystal clear with superb resolution and is well layered. Each component of the music is very well separated. I even noticed that for the first time I was able to follow the notes and not just hear the fourth guitar on Ecosystem’s Dilemma. Even songs that I considered to be “low-resolution” sound much more pleasing than normal.
The bass presentation can vary from just north of neutral on the lowest setting, reaching still very deep. This allows listeners to focus more on the mid-range and high frequencies suitable for vocal centric songs. However, even on the highest setting it still sounds natural and controlled, still no bleed to other regions. I left my setting on the highest no matter what music I listen to because the IEM is capable of such high degree of control. It doesn’t make an unnecessary boom / veil when uncalled for. The bass comes in only when it’s needed and is so high in resolution that it makes the CKR9LTD which I considered to be one my best to seemingly sound muddy in comparison. In the manual it is recommended that for vocal songs that the bass filter is changed to the clear (lowest) one, but to me, this only reduces the richness of the song. Again as I’ve said earlier, even on the black (highest) bass filter, the mid-range is still crystal clear.
The bass is to me, characteristic of a very well tuned dynamic driver, having just the right amount of punch and rumble while staying in control. Often, however, such single dynamic drivers is compromised in the upper frequencies at the cost of having amazing bass. The FLC8S doesn’t suffer from this as it is a amazingly tuned hybrid 1BA 1dynamic earphone.
The soundstage ! The soundstage makes songs very immersive, it produces an out of the head experience with each musical component placed not just in a 2 dimensional (wide) presentation but is capable of making music sound truly 3 dimensional (deep and wide). I have listened thoroughly through songs that I would normally skip, as songs that are not even in my preferred genre sound mind blowing. It makes me appreciate every song in my library, which is really something that no audio product was capable of.
All of these in addition to the great fit of the IEM makes it all the better. It simply fits. I can’t elaborate too much on this; the curvature of the IEM matches so well with the ear. Once you put it in it just stays there and you’ll forget you will hardly notice its presence.
Note that the IEM doesn’t stick out, but you still can’t sleep on your side with this IEM.
In conclusion the FLC8S is an astounding IEM capable of producing sound in high degree of resolution. The tuning system is a huge bonus that allows users to tune the FLC8 to suit their music genre of preference. The soundstage and technical capabilities of this IEM even without the tuning system is enough to distinct this IEM from the others. Despite this, the FLC8 can be improved with a softer, less microphonic cable and the tuning system isn’t perfect as small parts can be lost easily.
Pro: rich yet natural sound, considerable as truly hi-res without the sticker, comfortable, tuning available to suit preference
Cons : easy to lose bass tuning plugs,  cable is microphonic, expensive-ish
If you have the money, buy it, give it a shot, seriously
This made me top picks (Aurisonics rockets and CKR9LTD) sound "meh"
Thanks Kamcok! Great review! I'm Forrest Wei, designer of the product.
The cable was braided by a special machine me designed, I can say that the cable is very unique, almost all cable with the same contruction need to be cut in the middle and joint together at the Y split, but our cable doesn't have the solder joints, the signal is not interrupted, better to the sound.
The "plastic" at the Y split is not plastic, it's heat shrink tube, it's very strong, please do worry the quality.
I bit. My review will be coming in a few days.
Thanks to all those who read and enjoyed the review.
As im on my phone i cant tag people fyi.

@Soundstige, joedoe hope you enjoy the iem as much as i did
@redtwilight, whaleshark12, thanks for pointing that out, i will edit it once im back from my trip

@flcforrestwei, i am impressed with youe product and i would definitely recommend it. I trust that cable and the y splitter is durable as you said. I dont have any problems with it, just stating some things that others may not like. I think you can somehow make the splitter easier to slide and make the cable softer so it will be less microphonic.

Even for those who cant stand the cable, its not difficult to find an aftermarket product to suit your liking