FLC Technology FLC 8S

  1. originalsnuffy
    Detailed, open sound. Massively customizable.
    Written by originalsnuffy
    Published Mar 6, 2016
    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.
    1. drbluenewmexico
      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!
      drbluenewmexico, Mar 6, 2016
    2. originalsnuffy
      Thank you Dr. Blue.  I started off with the tuning that you were using and did not stray too far!
      originalsnuffy, Mar 6, 2016
    3. Paulus XII
      Interesting reading originalsnuffy. Always appreciate other trained ears people thoughts of FLC8S. It's still my favorite IEM.
      Paulus XII, Mar 7, 2016
  2. soundstige
    A complete game changer.
    Written by soundstige
    Published Dec 12, 2015
    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.
  3. PinkyPowers
    The Virtue of Versatility
    Written by PinkyPowers
    Published Jan 5, 2018
    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.
    FLC8s 06.jpg
    ~::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!”

    Unboxing 01.jpg
    Unboxing 02.jpg
    FLC8s 05.jpg
    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.

    Case 01.jpg
    Case 02.jpg

    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.

    Filters 01.jpg
    Filters 02.jpg
    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.

    FLC8s 02.jpg
    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.

    FLC8s 04.jpg
    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.

    FLC8s 03.jpg
    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.

    FLC8s 01.jpg
    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.

    FLC8s & Opus2 03.jpg
    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.

    FLC8s & N5II 01.jpg
    FLC8s & M3s 01.jpg
    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.



    1. FLC8s & DX200 01.jpg
    2. FLC8s & Opus2 01.jpg
    3. FLC8s & Opus2 02.jpg
      harry501501 likes this.
  4. angelo898
    hard to argue with the value
    Written by angelo898
    Published Dec 18, 2015
    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. 
      DJScope likes this.
    1. DJScope
      Thanks for joining the tour, mate! Cheers!
      DJScope, Dec 18, 2015
    2. Arsalan
      Thanks for your review, which one is better choice? DUNU 2002 or FLC8s?
      Arsalan, Aug 8, 2016
  5. Wiljen
    FLC8s - maybe the best $500 IEM that $300 will buy
    Written by Wiljen
    Published Nov 6, 2017
    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.
    outerfilter.JPG inner filter.JPG Nozzlefilter.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.


      mgunin, Katie88 and ngoshawk like this.
    1. Mmurin
      Which one are your sources for these IEM (DAP, smartphones..)?
      Mmurin, Mar 9, 2018
    2. Wiljen
      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.
      Wiljen, Mar 9, 2018
  6. kevingzw
    A Diamond in the Rough
    Written by kevingzw
    Published Mar 24, 2016
    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 sh*t 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.
      Dopaminer, B9Scrambler and hqssui like this.
    1. View previous replies...
    2. Trialanderror
      Just received a pair; really, really like them.
      Trialanderror, Mar 25, 2016
    3. RebeccaSugar
      Black+Red+Gold Master Race
      RebeccaSugar, Mar 27, 2016
    4. Arsalan
      Thanks, which one is better choice? DUNU 2002 or FLC8s?
      Arsalan, Aug 8, 2016
  7. svyr
    excellent hybrid with a few buts
    Written by svyr
    Published Jan 3, 2016
    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


    20160103_172750.jpg 20160103_172732.jpg 20160103_172810.jpg
    20160103_172846.jpg 20160103_172849.jpg


    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
      canali, H20Fidelity and DJScope like this.
    1. canali
      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.
      canali, Jan 3, 2016
  8. FUYU
    Triple Hybrid done right! - The FLC8s
    Written by FUYU
    Published Nov 22, 2016
    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.
    1. View previous replies...
    2. earfonia
      Good review! Thanks!
      earfonia, Nov 23, 2016
    3. AncientOne
      Congrats on another good review.
      Looking forward to read your take on those PM4 by Trinity...
      AncientOne, Nov 24, 2016
    4. Flcforrestwei
      This is a great review. Thanks!
      Flcforrestwei, Nov 27, 2016
  9. n05ey
    The little known package with a big sound
    Written by n05ey
    Published Nov 15, 2015
    Pros - balance, unflappable balance and pretty much everything else
    Cons - cable a little springy and microphonic
    FLC tour – The little known package with a big sound
    Where to start on these little guys… Firstly, thanks to Forrest at FLC Technology and @DJScope for putting together this tour. It is always a privilege to be a part of a head-fi tour and this one was no exception.
    Me and My Bias
    I do acknowledge that I have a couple of inherent biases. Many talk about the obligation to the review and their inherent sound bias, I will own the second but the first I find myself not conforming to very well. I have noticed that I appear to have the opposite. I love my own gear due to the need not to spend more money and the research and investment that I have made. This means that I have found it easier in the past to not see quite the same value in the brief flings with review units. I work to counter that bias and will note it later in the review.
    On the sound sig bias, I grew up as a bass head who swiftly turned into a treble head coming to head-fi and working through oldest to newest:
    Hippo-VB->shure 425->UE900->ety er4s->dunu titan 1
    Also along the way journeying in the world of over ear and on-ear:
    AKG Q701, UE6000 (a real outlier) and now the Grado 325e’s
    But to temper that treble tilt sound bias I thought I had better inform you of my latest passion, the Aurisonics Rockets. These have a receding treble but they are non-fatiguing and have such a beauty, delicacy and shimmer to the treble that I can forgive it (and turn it right up).
    So all that to say, think as you will of me and my bias and take a moment to understand it before you read my thoughts on a product that you may invest your hard earned on J
    To me this package is sublime. Initially you are greeted with a relatively plain cardboard box which has a nice heft to it and not too much give. From there you lift, turn and twist to open out this origami masterpiece into segments revealing parts of the impressive kit in their glory. You get the tuning kit, lots of tips (the large dark silicone fit me better than any of my alternative tips), the iems themselves (nicely presented and packed), tweezers (which are practically useless) and a screw top case.
    I think the case while a little bulkier and heavier than most is absolutely stunning. I love the finish and I love the sound it makes as you unscrew it. It has that slick metal on metal sound that has no grate or gravel to it, just the perfect glide…
    The iems themselves have a beautiful soft blue translucent colour, a colour that is used seamlessly across all aspects from the cable to the plug. I think it is beautiful and almost has a glow from the inside (which it doesn’t, just my gushy language) and I personally really like the aesthetic of the plug. It is all vaguely reminiscent to me of my old UE900 package reinterpreted, even the cable reminds me of it, although not so positively.
    The cable I found to be a little springy and scratchy. It didn’t hold a nice shape and wasn’t soft and supple which to me a great cable should be. It also managed to transmit more microphonics than I thought was possible for an over ear configuration… However I personally found the earguide area fine and the whole thing in the end disappeared when I turned on the music.
    Listening - tuning
    This thing is HARD to characterise with its multiple tuning options and so I thought I would just give an overall character based on my fav configuration, the red sub bass, the grey midbass and gold screw in nozzles with notes about a few of the other arrangements I had time to try.
    I personally found that the overall soundstage and imaging were pretty consistent regardless of the tuning with key areas of the spectrum moving forward and back rather than the whole character changing. I thought that was a really nice touch!
    Bass – The bass on these can be powerful! In the red/grey config they have a great punchiness to them without getting into the fuzzy zone. The fact that they retain a razor image makes me feel that they have a great balance even though they are capable of hitting hard. Adding in the high midbass filters changed the character a little toward the wooly side of things though never too much that it became a mess.
    Mids – With the gold nozzle the mids came a fraction forward in the mix which is my preference. They seem to be solid, a nice middleground. I never found the mids to be super seductive but I also never found them to be too dry either. They were just there, crystal clear, detailed to the full and well imaged so that you could place each instrument in its space with a clarity between them.  
    Treble – Lovely, just lovely. Nice, crisp and quite extended with nary a pain. I could listen to these all day without getting sick of it!
    Sound stage – I found the sound stage to be quite well defined. It is a large room with good height and width. I found that the impactful bass gives a slightly smaller room feel than the rockets, although rockets seem more up front. To be honest, it lays the whole sound out with space and I could listen and mentally travel around the space because it is combined with that razor imaging
    Imaging – razor, everything has a space and doesn’t reverb/clash. Need I say more?
    Please don’t make me send these on…
    They are great. They are a beautiful set of in ears that I would gladly purchase should I not fear the quality of my home life if I were to do so :)
    For the price you get so much and have the opportunity to really listen to the detail of the music that you miss in other in ears.
    My only minor complaint and minor indeed it is, would be that some more coloured sets can really feature a sound, like for example vocals whispered to your very soul tingling the spine or other such pronounced detail. These don’t do that, despite the tunability I found that everything was still there, in its balance just pronounced a bit more. Unflappable these are!
    To me the major accomplishment of these is that you never feel like you have to analyse the music. The detail is there, the ability is there, but it still feels like music and in the end you can zoom in on detail or just sit there and enjoy the tunes.
      soundstige, JoeDoe, DJScope and 2 others like this.
    1. View previous replies...
    2. Kundi
      Website showing full price now, and it's sold out. And i'm an idiot for not buying last week...
      Kundi, Nov 16, 2015
    3. Flcforrestwei
      There will be some discount for Thanksgiving, please check LMUE tomorrow.
      Flcforrestwei, Nov 24, 2015
    4. Arsalan
      Thanks, which one is better choice? DUNU 2002 or FLC8s?
      Arsalan, Aug 8, 2016
  10. Ambient Lights
    The Most Universal of All Universal IEMs
    Written by Ambient Lights
    Published Nov 23, 2017
    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 the 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 1-2kHz 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.

    FLC 8S.jpg

    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 (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. Comply TX400 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 Comply TX400 - an incredibly even and harmonious tone awaits you with this pairing.

    FLC 8S Hybrid Headset.jpg


    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 7N 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!)

    75 Ohm Impedance Adapter, FLC 8S + Silver Crystal Cable.jpg

    75 Ohm Impedance Adapter

    By now, I have been listening to the FLC 8S (with 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, 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 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 to crackle/be affected by electrical noise. Neutron's compressor with the following settings can be used to eliminate crackling/clipping 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 configuration of

    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)
    Attenuation, dB - 4.30. 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

    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 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 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 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 - Best option

    Dither - 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

    - Custom Format - On

    Settings Under Custom Format

    - 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 - Everything selected but FAST (feel free to enable everything listed under this setting)

    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.

    FLC 8S configuration

    Red | Clear | None + 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

    - 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.

    This is my subjective perceptions of the improvements I've noticed. While I can definitely pinpoint the more defined bass (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 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.

    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 ~1.3kHz to somewhere closer to 2kHz (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 the sounds from the balanced armatures are leaked out (and somehow increases midbass significantly while still retaining mids and highs when you go with no filters here, no idea how that works but it does). 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 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. As such, these probably controls the presence of the higher end frequencies, and 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 actually prevents the high end frequencies from going out of the IEM, 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 5kHz (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 6kHz). 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 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 ~2kHz range while reducing treble noticeably around 8kHz (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 ~1.3kHz and ~9kHz 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.
      pouyazarif, BrianLHR, mgunin and 3 others like this.