FiR Audio Xenon 6


100+ Head-Fier
FiR Frontier Series: Ne5 vs Kr5 vs XE6
Pros: -Unique warm tuning
-Rumbling kinetic bass
-Outstanding details (esp for warm iem)
Cons: -Too warm as a daily iem
-Vocal esp female is too recessed
FiR Australia Tour: Ne4, Kr5 & Xe6 Impression

I have been extremely fortunate to be loaned 3 FiR Audio latest iems as part of FiR Australia Tour:
-Neon Ne4
-Kyrpton Kr5
-Xenon Xe6.
I want express my big thanks to FiR Audio, Minidisc Australia and @Damz87 for organising this tour.


My DAC/Amp for this impression are Chord TT2, Hugo2 & Sony NW-WM1ZM2
Stock cables and default silver ATOM modules were used for all iems in this review.

FiR Neon Ne4
Ne4 is a warm iem with boosted bass/lower mid. The mid and treble are relatively flat. It has smooth sound presentation in which the harsh edge of notes seems to be rounded. This gives analog feeling that reminds me of my R2R DAC.

FiR marketed their kinetic bass as “bass you can feel” and I totally agree. I can not only hear the bass but also feel the impact - like having a mini subwoofer in your ear. The bass punches deep and wide.

The mid is excellent for most cases. The elevated upper bass gives extra warmth/boominess to the vocals. It sounds lush, fuller and weighty. Male vocal sounds magical with this iem. However, in few tracks, female vocal can sound unnaturally too bassy. Also, depending on the music, it can sound too sluggish and thick.

Ne4 treble is too mellow for me. I wish it has slightly more sparkle.

Detail retrieval is very good -it’s better than my UM Mest Mk2 – however, it sounds grainier compared to its bigger 2 siblings. In term of space, Ne4 feels like the most intimate among these 3.

FiR Krypton Kr5
In term of sound presentation, Kr5 is the opposite of Ne4. It is leaner, drier, more aggressive and brighter with more emphasis on upper treble and mid.

Similar to Ne4, Kr5 also has a kinetic bass which is capable to hit hard. However, it has a lot faster decay and cleaner than Ne4.
Kr5 vocal sounds more natural and not as warm as Ne4. Kr5 has forward and rich vocal but can be too lively. The vocal is nimbler and not as weighty as Ne4.
Kr5’s lower treble is well controlled. However, its mid/upper treble is piercing and fatiguing.

In term of space, Kr5 has an amazingly airy, spacious soundstage with good depth and holographic. Kr5 has excellent definition and has the best detail retrieval among these 3 iems.

FiR Xenon Xe6


Xe6 is a V-shape iem with strong focus on bass, recessed mid and slight treble sparkle. Sound-presentation wise, it’s more on the relaxed side (similar to Ne4) than the aggressive Kr5.

Xe6 takes an already excellent Ne4’s bass quality one or two step up. Texture-wise, Ne4 bass feel more like a 1D punch where you can feel the depth., Meanwhile, Xe6 bass is more like a 3D slam where you can feel not only the depth but the surface vibration. I have never experienced this so vivid bass rumble with iem!

Unfortunately, vocal is not Xe6 forte. It sounds dull, lack of harmonic richness. The vocal seems to be disengaged and does not blend well with bass and treble. This incoherence makes feel like I’m listening to bass with mid thrown in as an extra.

In term of quantity, Xe6 treble has just enough. Its not as forward as Kr5 and not as recessed as Ne4. It has realistic treble. Imo, Xe6 has the most pleasant treble of among these 3.

Xe6 has a very good detail retrieval, better than Ne4 by quite a margin and slightly below Kr5. Soundstage-wise, Xe6 is more intimate and has less wide than Kr5 but still more spacious than Ne4.

Currently, I own Empire Ears Evo and Odin.Based on sound signature, Evo competes with Xe6 as fun iems. Odin and Kr5 compete as a more well-rounder analytical iem.

FiR Xe6 vs Empire Ears Evo


Xe6 and Evo share similar trait – both are bass heavy iem with effective bone-conduction driver which you can feel the bass. However, they sound different.
Xe6 bass resembles slam with ability to rumble. Evo bass is more akin to big punch. Evo punches slightly deeper but tighter than Xe6. Evo bass is cleaner than Xe6 -possibly due to faster decay than Xe6 but it is also less fun than Xe6.

Xe6 has more elevated upper bass which gives extra warmth to the vocal. While, Evo vocal is more neutral. Evo mid is also more forward, richer and livelier – while Xe6 is more laidback.
Treble in Xe6 has enough sparkle and sound natural – while Evo has roll-off treble which make it sound darker.

Evo’s detail retrieval is no-slouch but Xe6 has better clarity. More texture especially in bass can be easier distinguished with Xe6.

Which one would I recommend? This is not easy since both are excellent performers. Would you be willing to give up vocal for a more visceral bass? Do you prefer more coloured iem? If yes, get Xe6. If you prefer more natural vocal at the expense of rumbling bass, get Evo.

FiR Kr5 vs Empire Ears Odin


Odin is more neutral than Kr5. Kr5 has more forward and bigger bass – while Odin bass is more tamed, tighter and better controlled.

In term of vocal, Odin is more natural and has more body – while Kr5 is warmer and leaner. Odin has more pronounced lower treble without being sibilant. Kr5 puts more energy on upper treble – which often I found to be too much. Odin has more intimate soundstage, while Kr5 is a lot more spacious and 3D like. Kr5 clarity is excellent but Odin is even better.

I would recommend Kr5 if you want a more fun iem with excellent bass and don’t mind Kr5 peaky treble. For a more balanced option with outstanding detail retrieval, Odin is what I would choose.

Ne5, Kr5 and Xe6 are excellent iem offerings from FiR that can challenge or even exceed other top-tier iems. Each model has its own flavour. If you prefer smooth sound, get Ne4. If you prefer a musically aggressive iem, get Kr5. If you prefer a fun sound with possibly the best bass among iems at the moment, get Xe6.


No DD, no DICE
Xenon 6: The Great Frontier
Pros: Unique, warm, thick and unashamedly coloured tonality
Powerful, dynamic and tactile bass response
Superb treble resolution, smoothness and extension
Impeccable technical performance despite the audacious tuning
Superb build quality, ergonomics and fit
Innovation everywhere - a breath of fresh air in IEM design
Cons: Tuning can be divisive for some, requiring extensive 'brain burn-in'
Tuning doesn't work for all types of music
Midrange clarity can suffer on tracks with too much midbass
Excess midbass impacts sub-bass quantity
Gold plating prone to microscratches
ATOM XS modules can be finicky to work with

Aside from a few notable exceptions, it’s rare for a new IEM to come along and completely change the game. FiR Audio’s Xenon 6 (Xe6), flag bearer of the Washington-based company’s Frontier Series that debuted in late 2021/early 2022, is one such IEM.

The entire Frontier series can be said to be pushing the boundaries with FiR’s Kinetic Bass technology in particular, but Xe6 is radically different over and above all the new technology crammed inside its small, shiny shells. From the very first listen, it’s obvious that this is an IEM doing stuff on its own terms, unapologetically breaking conventions and defying what most people who pay the sort of highbrow money it commands generally look for.

All of this should, in theory, make Xe6 an outlier, a marginal success at best. But instead, Xe6 has smashed its way to the top of the popularity charts, beating off competition from other fancied high-end IEMs that cost more, are tuned more conventionally, or would normally be considered a ‘safe bet’, as much as that’s possible in this fiercely subjective hobby anyway.

Despite its success, Xe6 is still divisive. Those that love it absolutely love it, and those that don’t can’t get it out of their ears fast enough. Rarely have I met someone who’s had a casual listen and wasn’t moved one way or another. This, I think, is Xe6’s true strength – it’s an emotionally evocative IEM in the best, and sometimes worst, ways. One thing’s for sure, it’s not going to bore you, or simply be iterative over what you already own.

In this review I’m going to do things a little differently too. I’ll cover all the basics, but won’t repeat most of what I’ve already written. Instead, I want to get to the heart of why this IEM is different, and try to understand what that means for anyone who dares to go against the grain to experience music in fascinating new ways.


Frontier Series

Before we turn our focus to Xe6, let’s cover off some of the interesting new technologies that FiR engineered into the entire Frontier Series, which also includes the ‘entry-level’ Neon 4 (Ne4), and ‘mid-level’ Krypton 5 (Kr5).


Kinetic Bass. Big bass in IEMs has always been something of an oxymoron. After all, when we think of big bass, we think floor-standing speakers or subwoofers, massive dynamic driver cones moving large volumes of air as low-frequency waves that we ‘feel’ as much as we hear.

As you can imagine, this trick is a little more difficult to pull off with a driver smaller than your pinky nail. Not that IEMs can’t reproduce impressively ‘big’ bass – heck many IEMs do so better than headphones with drivers ten-times their size. But getting that much bass air to ‘move’ in such a small space is generally detrimental to just about every other frequency that comes after, often resulting in a thick, muddy sound that’s not particularly hi-fi.

Kinetic Bass literally flips the script on traditional dynamic driver designs. Using an outward-facing dynamic driver beneath an open-vented port above the IEM nozzle, low frequency sounds are transmitted directly into the inner-ear through the bone cartilage, in a process known as bone conduction. This allows the full spectrum of bass energy to pass through your ears in the same way that it does using full-size speakers, through air and bone conduction, which, in theory at least, makes the bass feel more immersive, extended and ‘real’.

Other IEMs use bone conduction technology to vibrate sound waves through the shell or ear tip, but no other IEM that I know of uses it specifically for the foundational bass frequencies through an open port, changing how we experience bass given the inherent physical limitations of IEM.


ATOM Venting. FiR’s Air Transferring Open Module is not a new technology for Frontier, but rather an existing technology adapted to better fit the new Frontier universal shells. ATOM is essentially a vent that releases air pressure trapped inside the ear canal, reducing fatigue and all but eliminating the reflex that causes your eardrums to protect themselves against prolonged exposure to loud sounds.

That’s not to say ATOM removes the failsafe built into your ears, but rather eliminates one of the main causes of listener fatigue, allowing you to listen for longer without the build-up of dangerous hearing-impacting pressure. It’s also not the same type of venting used in most ‘vented’ IEMs, which only serves to remove the pressure that builds up inside the IEM itself due to the air movement of the various drivers. That type of venting protects driver performance; ATOM protects your hearing.

Other benefits of ATOM include the perception of a larger soundstage due to improved airflow and reduced isolation. The flipside is exactly that – reduced isolation – so you’re more likely to hear environmental sounds using the most open ATOM modules. Of course, changing the level of isolation also changes the perception of certain frequencies, which means you can tweak the tuning of Frontier Series IEMs by swapping out different ATOM modules.


Open Acoustics. Most IEMs use drivers connected to sound tubes that direct sound through the nozzle into your ears. Frontier Series IEMs use a combination of three elements: open drivers, a sound reactor and a sound reflector.

All the drivers inside Frontier Series IEMs are open drivers, so they radiate sound directly outward into the IEM chamber. The sound waves pass through a sound reactor, which hones and refines it without resorting to dampening or filtering that would otherwise degrade the signal. There’s also a single high-frequency open driver that sits outside the main drivers (which are in the nozzle shaft), and fires at a sound reflector directed straight at the ear canal.

The end result of the different parts that make up the open acoustic system is a smoother, less brittle and highly dynamic sound, with excellent extension at both ends.


RIGID System. If there’s one aspect that’s often overlooked in the modern industrial design of many IEMs, it’s build quality. Thankfully this doesn’t apply to Frontier Series. Not only is the artistry, material quality and assembly of the Frontier IEMs exemplary, they also use a series of highly-resilient ‘RIGID’ parts to improve reliability.

These include what FiR claims to be the most durable 2-pin connector in the industry, rated for 1,000-plus connections, and a quadrant design that prevents the 2-pin socket from coming loose. Each Frontier Series nozzle is also fitted with a RIGID snap screen, an acoustically transparent steel mesh screen that prevents dirt and debris from reaching the IEM’s internals, and can snap on and off for easy replacement.

Two other RIGID technologies are used exclusively on the custom versions of Frontier IEMs, which we’ll hopefully get to review in a future article.

Taken together, these four technologies – some evolutionary, others revolutionary – make FiR’s Frontier Series IEMs some of the most advanced premium monitors you can buy, at least from a usability and longevity perspective. Each IEM goes beyond the core technologies, with varying driver configurations and tuning, to deliver a different sonic experience.

However, where Ne4 and Kr5 ‘toe the line’ in terms of the more conventional tonal and technical performance expected of high-end monitors, Xe6 tears up the script with a risky attempt at utterly unconventional. Does it work? Let’s find out.

Xenon 6

Packaging and presentation
. FiR was clearly going for a ‘retro’ feel for the Frontier IEMs if Xe6’s spartan yellow/gold box with its basic back-to-the-60s industrial-style line illustrations is anything to go by. It’s different for sure, and I suppose you could call it modern-chic at a stretch.

Beneath the slip-cover, the box itself is a more traditional matte black with gold foiling lid-top, made of a thick-set cardboard. Removing the lid (which takes some dexterity as it’s very snug) reveals a cover letter with some poetic words about Frontier by FiR co-founder and CEO Bogdan Belonozkho, with warranty details and a short user guide on the reverse side.

The IEMs are nested in a plush foam cutout panel, pre-attached to the cable, which itself is rolled up beneath an iron-on Frontier Series badge that wouldn’t look amiss in a Tom Cruise movie.


Removing the top shelf also reveals the well-made leather storage case, inside of which you’ll find the spare tips (silicone and foam), a cleaning tool, the (micro) ATOM module holder, and the ATOM removal tool. The IEMs I received were shipped with foam tips pre-installed, which I immediately removed and replaced with my own silicone tips.

While it’s not the most lavish presentation I’ve seen at this price point, the whole look and feel is very satisfactory. The large leather storage case that also holds spare accessories is a nice touch, and the small design cues add to the feeling of a ‘themed’ IEM rather than just a generic IEM unboxing. Speaking of which, if you haven’t seen my unboxing video from the initial impressions overview, here it is again:

Accessories. In terms of accessories, the two most important are the stock Scorpion cable and the ATOM modules. I expect to see a good stock cable included with expensive IEMs, and the 8-wire 26AWG silver-plater copper Scorpion cable is just that. It feels well made, comes standard with a gold-plated 4.4mm Pentaconn connector, and is supple, light and kink-free. It’s also a very good match for Xe6 sonically, so there’s no need to search for an aftermarket option to maximize its performance.

The ATOM modules are without question one of the best features of the Frontier Series IEMs, but why FiR decided to shrink them to almost invisible dimensions (for the universal models – customs get the full-size modules) is anyone’s guess.

Changing the preinstalled ATOM modules is a pain in the tush, to put it mildly. Because they ‘screw in’ with a rubber gasket, you have to cajole them out of the IEMs, tilting the ATOM tool this way and that until the module ‘pops’ out. Do this very carefully, on a flat surface, preferably over some sort of container than can catch the module when it inevitably drops from the IEM (I used the carry case for this). Thankfully reinserting the modules is much easier than removing them, but again, do this slowly and carefully.

The included tips are nothing special, just a set of silicone and foam tips in three different sizes. I tried the small silicone tips briefly, which were too large for my ears, before finding a good aftermarket set that fit me better. Xe6 is quite responsive to tip swaps, and the sound can change quite dramatically based on the tips you choose. I really like Acoustune’s AET07 tips for their comfort and sound profile – especially in the midrange – but ultimately have settled on JVC’s Spiral Dots for their supreme comfort and easygoing sound.


Design and fit. From a technical perspective, Xe6 is the most advanced of the Frontiers. It’s the only tribrid IEM in the series, comprising a Kinetic Bass dynamic driver and a BA woofer for lows, a set of open BA drivers for mids, an open BA driver for highs, and a set of electrostats for ultra-highs (>12KHz).

Impendence is a fairly low 28 ohms, but there’s no flat impedance technology like there was in FiR’s previous IEMs (similar to the LiD technology used by 64 Audio and FIBAE technology used by CustomArt). This means source impedance may affect Xe6’s sound, something to keep in mind when auditioning sources.

The universal shells are extremely well made, with precision seams and expert surface plating. The gold finish is susceptible to microscratches, so if you’re someone who’s particular about keeping IEMs looking new, take extra care when handling or storing. The nozzles are medium length and quite thick, but not as thick as some other IEMs I’ve recently tried.

Fit is a very personal thing, but the shells seem to fit me fine. I use small size tips for my small size ear canals, and found several options that I could use to wear for hours without fatigue. Despite being made from metal, the earpieces are quite light, and won’t pop out your ears unprovoked. The earguides on the cable also provide comfortable support for the earpieces, so overall, it’s all good on the wearability front.

In summary, the packaging, presentation, accessories, design and fit of the Xe6 universals are top shelf, befitting their lofty price. Beauty is in the eye of the beholder, so whether or not you like the high-gloss gold bling with its sapphire glass and blue speckled inlay is not for me to say. What’s undeniable is how different these IEMs sound to just about anything else I’ve heard in the hobby, so that’s where our focus turns to next.


Sound Impressions

. Xe6 is first and foremost a warm, coloured, ‘fun’ IEM. Its tonality is characterised by a massive midbass and lower midrange shelf, an unusual tuning choice which pushes up the levels that more mainstream tunings (even ‘fun’ tunings) push down. There’s no linear bass with a midrange ‘cut’ to separate bass and midrange; instead, there’s a doubling down on big bass and mids.

Everything Xe6 does is based on some or other variation of its thick-but-clear personality. A vocal performance with a forward bassline will have you thinking that everything sounds too thick and warm, and yet when the singing begins and higher-frequency instruments start playing, there’s somehow no veil.

Despite its quantity, bass delivery is of exceptional quality too. Sub-bass focus suffers a bit because of the overabundant midbass, but there’s still some rumble when called for, and the midbass isn’t so loose that it spills all over the mids and highs. This is probably the result of Xe6’s unique combination of Kinetic Bass and a dedicated open balanced armature woofer, giving you ‘the best of both worlds’ when it comes to bass delivery mechanics.


The elevated bass and, more significantly, ‘overcooked’ lower mids would have been a bigger issue if the quality of the mids wasn’t so good. Instruments are full and weighty, yet still quite fast, with a pleasant, natural decay. Vocals, both male and female, are lush, warm and organic, but more importantly very, very smooth. There’s no harshness here, and the resolution of the open drivers is such that the smoothness doesn’t come at the cost of detail.

The same resolving smoothness extends to the treble, which is some of the best I’ve personally heard from an IEM. Keep in mind I like treble to take a small step back from the main performance, to give the overall presentation just enough sparkle and air, and then get out the way. Xe6 does this, but it also doesn’t roll off any high notes, and its use of an e-stat to add air up top without making everything sound ‘electrostatically ethereal’ is very clever indeed.

It’s hard for me to sum up Xe6’s tonality like I would most other IEMs. Is it a U or a W, for example? Depends on the track, sometimes it’s both. It can also be a V, with the mids taking a back seat, and it can be a reverse J, with everything subservient to the bass and lower mids with a touch of added air up top.

Tonally, Xe6 is like a chameleon, and although warm, thick and bassy are a given, they’re not always going to define what you actually hear once the music starts to play.


Technicalities. I think the reason Xe6 is so adaptable despite its exaggerated tonality is because of its technical performance. Resolution is top-shelf, and the stage, while not the widest I’ve heard, has a grandness of depth and height that few IEMs can match.

For a warm IEM, Xe6 can also deliver the goods, with the right music, with an ink-black background and impressive separation and layering of vocals and instruments. Sure, when the bass is let out the cage or the lower mids are pumped up in the recording, the finer nuances take a back seat, but I never feel like Xe6 has lost control at any point.

That could be because of all the IEMs I’ve heard, Xe6 has some of the better dynamic swings in the business. It can play tiny nuances in one instance and flip the switch to full-throttle explosive in the next movement.


This makes it an interesting choice for more conservative genres like large orchestral music, where big, brash and warm aren’t your go-to keywords, but in many ways it’s like listening to a performance at a live venue when you’ve had just enough to drink to make sitting through a classical ensemble seem almost…pleasant.

I jest of course, but I keep going back to the idea that with Xe6, you’re not hearing what you expect to. Still, because it’s so competent technically, the quality is good enough for even the more conservative among us to look past the tuning quirks, if indeed that’s how you hear them.

Technically, Xe6 can comfortably sit at the same table as some of the technical specialists of the IEM world, like Traillii, Fourté and Mentor, and while I don’t think it can replace any of those esteemed IEMs, I know which one I’d rather use most of the time.

Listening notes

Since this is a deep-dive review of Xe6, it won’t be complete without some detailed listening notes from my many sessions with it. Consider these stream of consciousness thoughts that I wrote down while listening, then tidied up to be legible enough to read and understand. Hopefully you’ll get some idea of what I’m hearing by reading the notes while listening along.

Note: all listening done with the HiBy RS8 as source, using low gain, and a maximum volume of 40/100. Xe6 is extremely easy to drive, so be careful when connecting it to more powerful sources.

Xe6 with…indie/pop

Lana Del Rey – Video Games
. Xe6’s thickness is apparent from the first note. The electric piano intro sequence feels like it’s being played in a reverb room. And then, Lana starts singing and her sweet, emotive voice is as raw and beautiful as I know it to be, presented clearly and completely unveiled by the low notes. Xe6 does a great job with the first of the sub-bass ‘drops’ at 2:22, which can be felt as much as it’s heard, and all the while Lana’s hypnotic voice remains the centerpiece. Some of the lesser elements are pushed out to the extremities, but they’re still there. Xe6 can be quite intense, and this rather laidback track is a good example of how that intensity manifests in music with a strong, defined bassline.

The Shins – New Slang. In contrast to Lana’s bold intro, the tambourine and guitar intro to The Shin’s now-famous New Slang is rich and detailed without overpowering the stage, even though some of the lower-range guitar plucks have that characteristic Xe6 fullness to them. The male lead vocals are a little less forward, partially swallowed up by the lower midrange elevation would be my guess.

There’s something about the dynamic swings Xe6 is capable of that makes this type of head-bobbing melody even more so, and it’s all I can do to type while nodding like a bounce toy. This is a great track to demonstrate the quality of dynamic driver bass in a song without drums – it sets up the foundations against which all the sparklier notes and vocals contrast, resulting in an utterly engaging presentation as good as I’ve ever heard it.


Xe6 with…Americana

Brandi Carlile – The Story
. The first thing I listen for in this track is the purity of Brandi’s opening vocals, and Xe6 doesn’t disappoint. There is a touch of bloom from the accompanying guitars, but it doesn’t make Brandi any less distinct. The second check on the list is kick drum impact, and Xe6 does a great job here too, the suckout of air from the drums clearly felt along with the texture of the drum hits.

When the instrumental melee begins mid-track, it is quite a bit thicker than I’m used to, and while every element is there, there seems to be quite a bit of warm air between the instruments. Going back to the simpler vocal passages is a relief from the thickness, but at the same time, as the song progresses, the warmth becomes more enveloping and comfortable. There are no hard edges here, but no smearing either. It’s the sonic equivalent of lump-free porridge of the tastiest kind.

Whitehorse – Dear Irony. Xe6 flexes some of its technical muscles with this track, throwing up an obviously wide and deep stage with the very first left channel guitar plucks in the intro, followed up by excellent separation of the female and male lead vocals, imaged precisely one behind the other. The vocals are contrasted against a thick bassline, which is very well done here, but does obscure some of the deeper sub-bass drums in the background.

What’s most important, though, is how emotionally the lyrics are delivered, and herein lies Xe6’s strength, its ability to subtly emote despite the sometimes overwhelmingly full sound. Vocals are absolutely clean – not a hint of grain or sibilance – and this is key to keeping the focus where it should be.


Xe6 with…modern classical/cinematic

John Barry – The Buffalo Hunt
(from Dances with Wolves). This is one of my all-time favourite pieces of modern classical cinematic scores, and The Buffalo Hunt is one of its highlights. What’s most impressive is how well Xe6 resolves the wide dynamic range, strings, toms and horns. Spread across a vast stage, every subtle cue is easy to pick out, and there’s not one element that dominates the others.

Xe6’s thickness is also a non-issue, with instruments sounding ‘correct’, full of texture, with accurate timbre. There’s definitely some warmth infused into an otherwise colder production, but this elevates and improves it in my opinion.

Lisa Gerrard – Now We Are Free (from Gladiator). A masterpiece film topped by a masterpiece soundtrack by Hans Zimmer and his muse, Lisa Gerrard. The goosebumps appeared for me just as soon as Lisa started singing, which is more than I can say for many IEMs I’ve heard this incredibly emotional track with.

For me that’s not just because her voice sounds so pure, but because the power of the deep, dynamic bass notes, subtle string cues, deep stage and gentle, quivering backing track all combine to take me right back to the powerful, tragic and inspirational scene where I first heard this music. It’s transcendent as much as it is perfectly presented.


Xe6 with…singer-songwriter/folk

Eva Cassidy – Songbird
. Is there a more iconic song than this to represent the genre, I wonder? The question for me before I pressed play was how much Xe6’s penchant for thick-set guitar plucks would interfere with Eva’s angelic voice and soft backing vocals. The answer, thankfully, is not at all. Yes, the guitars are prominent, but so is Xe6’s ability to forward-project female vocals.

Once again, not a hint of grain or sibilance, and when Eva hits the high notes, they’re so sweet that the tragedy of her passing can feel overwhelming. I really like how the accompanying shakers, and even the subtle strings in the deep background are clearly heard, but unlike some overtly technical IEMs that compartmentalize the sounds – impressive as that may be – they’re presented here as an even more impressively cohesive and musical whole.

Jim Croce – Time In A Bottle. What is it with me and tragic singer/songwriters? This is a simple recording that’s not so simple to reproduce well. It’s a thinner, colder recording that can sound harsh with some IEMs, but with Xe6 it’s nothing but smooth, detailed and completely captivating. Jim’s vocals take a small step back to the guitars in the left and right channels, but that’s a good thing as his voice can sound overly forward on this track. Xe6 makes it feel like I’m sitting in a room with Jim, guitars strumming to either side, and him just out of reach, as if foreshadowing what comes next so soon after this recording was made. Beautiful and sad, and Xe6 captures both so well.


Xe6 with…Classic Rock

Def Leppard – Love Bites
. My personal pick from an album full of personal picks, Def Leppard’s Love Bites is lifted directly from the soundtrack of my youth. When I listened to it on endless repeat as a teenager, however, I wasn’t using such resolving and sophisticated gear. Xe6, with all its resolving power, takes me back to that time, because its smoothness, warmth and relaxed, rounded treble combine to tone down many of the harsher edges from this less-than-perfect, often too-bright recording.

What’s left is perfectly centered vocals, bouncy bass drums and guitars with crunch that I can enjoy without wincing. Cymbals and splashes are liquid-smooth, just as I like them, and the vocals have some added fullness to them too. Most importantly, the groove is absolutely on point. Brilliant stuff.

Bon Jovi – Runaway. As a teen I used to bounce between Def Leppard and Bon Jovi as my two anthemic ‘rock’ bands of the 80s and early 90s, and to this day they’re about as heavy as I like my music, with very few exceptions. There’s something about Xe6’s ability to fill out the rather meek bass drums of these older recordings too that takes me right back to when I used to blast these tracks on a 2-channel system with much bigger drivers.

I also like that there’s no harshness in the guitars, and Xe6 easily keeps up with the pace of the drumming and riffing in this classic track without any smearing or overlap. I can only think that those who prefer more grunge might find this presentation a bit too polite, but for me, it doesn’t get any better. In fact, I think Xe6’s thicker sound is probably better with these older recordings, before compression and the loudness wars took over the music industry.


Xe6 with…electronic/dance

Ilan Bluestone – Will We Remain
. This is a newer track in my test library and a genre that is quickly becoming more than just a passing interest. I’ve never been into the dance/trance scene at all, but it’s music that I can lose myself in for hours – thankfully without the accompanying crush of gyrating, sweaty humans around me. Leaving real instruments behind makes it easier on the IEM for sure from a tonal perspective, but puts added emphasis on technical performance.

This is where Xe6 earns its stripes as a top-of-the-line performer. Every sonic nuance is important here, and the interplay between the different sounds on Xe6’s massive stage is captivating. This track in particular pushes Xe6 to the limit at both ends, with some very tight, taught bass notes followed by airy, spritely treble notes that need to be precisely imaged but not too forward or energetic. Xe6 pulls off this balance without breaking a sweat.

Armin van Buuren – Intense (featuring Miri Ben Ari). I keep going back to this track for its combination of modern classical and electronic elements, and also one of the few non-vocal electronic tracks I use to test gear. The beauty of Miri Ben Ari’s violin strings is always a highlight, and Xe6 absolutely nails the texture, timbre and realism here. The deep bass of the double-drop makes a perfect contrast with the strings, before the electronic elements and dance groove take over.

Xe6 manages to not only keep pace, but completely avoid any smearing. Sub-bass isn’t the deepest I’ve heard with this track, but the lower levels of midbass in the track help keep the performance clean and bloom-free. Once again, Xe6’s speed, dynamic contrast, imaging and resolution are on full display here, with Kinetic Bass taking care of the groove.


In summary. I’ve limited my notes to music I know well and the genres I mostly listen to. Of course, there’s so much more that I couldn’t include, and that goes for my own library, never mind the stuff I don’t ever listen to. Regardless of the music you listen to, one thing’s for sure: you can expect Xe6 to add colour, even though the way it does it isn’t always what you’d expect.

If you’re looking for a ‘reference’ tuning, this is not an IEM for you. But even if you’re looking for something fun and wild, Xe6 won’t always be that either. It really depends on how its tonality intersects with what you’re playing, and that’s what makes Xe6 such an exciting listen in many ways – you never quite know what you’re going to get.

Select comparisons

Sony IER-Z1R
. Sony’s flagship is my ‘reference’ IEM, even though it’s far from what most consider reference sound. Xe6 is easily its equal, but in my opinion, not its rival.

I hear Xe6 and Z1R to have very different bass profiles, Z1R leading with a deep, liquid sub-bass and linear midbass, Xe6 the reverse, with a sub-bass supportive of an elevated midbass. Both have bass quality and texture that exceeds just about any other IEM I’ve heard, including Empire Ears’ bass champions. But, where Z1R’s bass is more even-keeled and balanced in the overall signature, Xe6 is always bass-first.

Midrange differs too. Xe6 has fuller mids, especially vocals, that are warmer than Z1R’s more neutral presentation. I don’t hear Z1R mids as recessed, though some do, and depending on the bass levels in the music, the same can be said of Xe6. Most of the time, however, both IEMs have some of the better mids I’ve heard, Xe6 being a touch more resolving, Z1R a touch more textured.

Z1R has more of a lower treble emphasis than Xe6, which doesn’t have any specific treble emphasis other than possibly a boost of air up top. Xe6 treble is smoother, silkier and more rounded, while Z1R is more incisive, detailed and sparkly. Both have superb treble quality, and I don’t really have a preference between them, enjoying both in equal measure.

Technically Xe6 is a touch more resolving, but Z1R casts a bigger, more cavernous stage, and its imaging and separation are at least on par. Both are very dynamic, but Xe6 even more so. Neither IEM loses too many points on technical performance, so the differences really come down to tuning and, for some, comfort and ergonomics.

Z1R is notoriously wonky in the ear for many people, while Xe6’s smaller, lighter universal shell should be a better fit for most ears. It’s not for mine, however, so an audition is really the best way to know which works best for you.


Unique Melody ‘Multiverse’ Mentor. I haven’t spent nearly as much time with Unique Melody’s co-flagship, but the time I did spend with it made it clear for me that it’s doesn’t have the same level of engagement for me as Xe6.

These two IEMs couldn’t be more different. Xe6 is bold and dynamic, with an inviting tonality that swings wildly between extremes. Mentor is more balanced, but also livelier and more energetic up top that gives it an oddly disjointed personality. Where Xe6 is rich, organic, and sometimes a little ‘loose’, Mentor is the definition of technical precision. Xe6 infuses music with a sense of tonal wonder; Mentor wows you with technical trickery.

For me, Mentor is not an IEM for bass lovers. For all its technical prowess, Mentor’s bass leaves me cold and unsatisfied. It’s the fly in the ointment of an otherwise impressive IEM, which becomes even more apparent when comparing it to the bass masterpiece that is Xe6. I know that’s not going to be a shared opinion by some, who take no issue with Mentor’s sub-bass rolloff and ‘balanced’ BA bass delivery as a whole. But for anyone who needs to feel the kick of a drum in a live performance, Mentor just isn’t the right tool for that job.

Nitpicking other differences between the two, Xe6 is by far the better-made IEM, with Mentor’s dullish exterior and structural ‘imperfections’ not quite up to the quality of Xe6’s pristine all-metal design.


Campfire Audio Supermoon. I’m only comparing Xe6 to Supermoon because I happen to have both on hand.

Supermoon is a custom IEM (though a universal version exists), so from a fit perspective it’s no contest in favour of Supermoon (though Xe6 is also available as a custom). Technically, Supermoon easily trades blows with Xe6 in all but dynamic contrast, which may or may not be as important to the music you listen to (and if it’s not, bonus points to Supermoon).

Where Xe6 overtakes Supermoon, in my opinion, is its tonality and timbre. Supermoon is colder and more ‘digital’ compared to Xe6’s warmer, more organic and natural tone. Supermoon also suffers from thinner mids, and the occasional metallic timbre in the upper-mid/treble region, whereas Xe6 is about as far away from metallic as you get.

None of this is to say that Xe6 is clearly the right choice for you over Supermoon. If you’re familiar with planar timbre and dynamics, you won’t have any issues adapting to Supermoon’s outstanding IEM-sized presentations of both. If you like your music superfast, resolving and clear, with world-class sub-bass to boot, Supermoon outdoes Xe6 there too.

Both IEMs are their own type of ‘crazy’ in many ways, and will appeal to those that don’t always want to play their music safe. In a way they’re kindred spirits, but definitely cut from very different cloths.

Closing thoughts

If Bogdan and his FiR Audio team wanted to make a bold statement about the state-of-play in the IEM market, Xe6 is about as bold as it gets. Here’s an IEM that doesn’t shy away from a smorgasbord of red flags: eye-watering cost, unapologetically boosted bass, unashamedly coloured sound…

And yet here we are. Xe6 is an enigma, an IEM that goes against the grain and yet garners far wider appeal than it has any right to. It ended 2022 as the number one IEM as voted for by members of the most popular thread on the world’s most popular portable audio forum. Having spent well over a month exploring my music library with this brilliant IEM, I can totally understand why.

Xe6 challenges how I listen to music, but it does so with an uncompromising degree of quality. From its meticulous build, the attention to detail in the design, and the cleverly creative technologies used to shape its sound, Xe6 delivers something completely different but also utterly engaging. It also compromises very little that’s important to the high-end audiophile in doing so.


Still, this is not an IEM for everyone. In fact, I wouldn’t recommend it as a blind buy. If you’re a one-IEM user, if your preferences lean more reference, if bright and light is your catchphrase, then Xe6 will more likely horrify than excite you. I’ve spoken to many who literally pulled Xe6 out their ears before the first song was done.

But, this type of reaction is nothing new for such a brave challenger to the status quo. I believe Xe6 will reward those who take the time to both find the parts of their library that work best with its presentation, and allow their brains to adjust to the way it presents those parts of their library that don’t.

There’s no question that, with some music, Xe6 will sound too thick, or too warm, or too relaxed up top. But, unlike many IEMs that bump the midbass and/or lower mids as much as Xe6 (are there any?), it doesn’t sound veiled, or bloated, or muddy. Sure, if you’ve just come off a session with a thin, bright IEM, your brain will need to re-calibrate. But once it does, you’ll hear how Xe6 lets all the detail through, creates a sense of space, and does it all without pulling back on its excesses.

This is an IEM that lets you have your cake and eat it too, even though it sometimes feels like it’s stuffing the cake into your ears and mouth and nose. It’s the most fun I’ve had with an IEM since I started in the hobby, and while I don’t think I can live on a diet of Xe6 alone, I can’t help but feel that a premium collection without it would be always be missing something special.


This review first appeared on The Headphone List.
Tex Irie
Tex Irie
Love the XE6.
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You are far more eloquent than me. Best I can say is “Xe6 Rocks Awesomesauce Dude!!”
Great Review. Interested to give these a demo so I will be looking out for these at this years London CanJam.
Listening to Eva as I write this. What a voice!
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1000+ Head-Fier
There’s something about Xenon
Pros: Insane bass you can actually feel
Gorgeous IEMs - basically a piece of gold jewelry
An emotional experience the Rn6 can't replicate
Something different from your usual $3k+ IEM
One of the best for casual listening
Good mids
Cons: Doesn't do well with critical listening
Scores poorly when analyzed
Bass bleed like crazy into mids
Terrible cable
Non-durable finish
Packaging is consistent with a sub $1k IEM
Xe6 Side.jpg

Original Logo Small.png


Up for review today are the “Love It” / “Hate It” FiR Audio Xenon 6 (Xe6) which I purchased used on the Head-Fi classifieds. With these IEMs, you either love their bass or hate their bass – I’m definitely on the “Love It” side of the spectrum, but it likely comes down to what your preferences are. These are FiR Audio’s most expensive IEM currently, but not technically their Flagship IEM anymore if you count the limited-edition Radon 6 (Rn6). The Xe6 does, however, come with gold plating and a stainless steel housing instead of the Rn6’s black aluminum housing. So, again, it comes down to your preference on which you prefer (and if the Rn6 is still available).

Both the Xe6 and Rn6 have the same 6 drivers (thus the 6 in their name) with 1x 10mm Kinetic Bass Dynamic Driver, 2x OpenDriver Balanced Armature Driver for mids, 1x OpenDriver Balanced Armature Driver for high-mids, 1x OpenDriver Balanced Armature Driver for highs (with Sound Reflector), and 1x OpenDriver Electrostatic Driver for ultra-highs. There’s also a ton of cool tech on these that push the envelope of what IEMs can do. The Kinetic Bass alone is worth the price of admission with an almost open-back design for the bass driver sitting inside your ear, which really does help you feel the bass, not just hear it. It’s like being in a live concert - wubwubwubwub.

You also have the ATOM vents which prevent pressure build-up on the ears, and you can adjust the tuning slightly with them as well. Lastly, there are no sound TUBES between the drivers and the earpiece which creates a bigger soundstage. The Xe6 also has sapphire glass face plates with gold fleck and a 1-year warranty. Overall, a very cool design – certainly class-leading in tech.

Xe6 Box.jpg

Accessories/Earpads/Eartips (6/10):

It’s OK. That’s the best I can do here since it comes with almost the exact same stuff as the $999 VxV…at 3x the cost. The box sleeve and box itself are less Magic The Gathering-card-holder box (VxV) and more luxury-watch box, but it’s nothing compared to the Elysium, Trifecta, or Mezzo LE. Inside the box, all you get are several sets of ATOM modules, which are tiny, a tool to remove them, and 4 sets of meh ear tips. I just threw my trusty Spinfit W1s on instead of messing with the stock ones. You get a cool FiR Space Force iron-on patch, though I have no idea why – nothing else really screams Space Force from FiR except for their occasional Space Bunny Logo. Still, a cool patch, but something I’ll never use. Really, that’s it, the bare minimum, which was acceptable on the cheaper VxV, but is unacceptable on the $3,900 Xe6. At least include more ear tips in a separate baggy if not in the case. As always, I'm using my Spinfit W1 tips since they're the best I've found (You can buy them here if you want a set:

Yes, the Xe6 comes with the ATOM venting modules which change the isolation the Xe6 provides. Most people feel the Black module may be the best for the Xe6 - but play around with them and you do you. The Gold module gives you the most isolation (and the most bass) while the Grey is slightly less isolation, and the Black is the least isolation. So, it makes sense why the Black module might be the favorite since it makes the Xe6 the most open back and tames some of the bass. Mine were tested below as they come from the factory – with the Grey module installed. But yes, changing the modules (which is a royal pain by the way) will change your tuning slightly and also increase outside noise – just like the 64 Audio series. 7/10 points here - you can do better FiR.

Xe6 Case.jpg

Cable (3/10):

Ugh. I hate the scorpion cable. It’s actually worse than the Aroma Audio cables – which I also dislike. The scorpion cable, so called due to the shape of the ear hooks looking like a scorpion’s tail, is the most tangly and annoying cable I’ve ever used on an IEM costing almost $4k. It kinks, has memory retention, is poorly braided, has gold accents that dent or scratch easily, and it’s actually worse than the Aroma Jewel cable, though quite similar to the Aroma Thunder cable. At least it’s 4.4mm, so that’s a plus. Still, FiR learned the lesson from this one when they released the Xe6’s brother, the Rn6 with a brand new cable that is one of the BEST I’ve ever encountered on an IEM – and it’s $700 cheaper than the Xe6. So, if you’re planning on getting the Xe6, budget for a better cable if you don’t already have one – at least the scorpion cable sounds good. But, the cable is so bad that FiR doesn’t even mention it on their site under the Xe6 page – it is mentioned under the custom-built cable section, which seems to be a completely different cable. So yeah, get a better cable - 3/10 points.

Xe6 Cable.jpg

Build Quality/Comfort (4/10):

Again, the poor Xe6 loses points here because, despite being made with stainless steel, the gold finish on the IEMs and the cable is extremely easy to scratch with tiny little scratches or even dents (as shown on the cable connector pic, no, I didn’t do that). Almost every single Xe6 out there has tiny little micro-scratches on it. Or, just a bunch of fingerprints because the Xe6 finish picks up fingerprints like an FBI fingerprint kit. I can just see someone getting arrested because the cops were able to pull fingerprints off his Xe6. The Rn6 fixed THIS issue as well with the sleek, durable black coating. Don’t get me wrong, the Xe6 is pretty gorgeous with the sapphire glass faceplate and $10 worth of gold flakes on the faceplates and the gold coloring – it’s just not very durable.

That stainless steel, while providing a nice heft to the IEMs is also one of the biggest complaints of the Xe6. They’re heavy. Tiny, the Xe6 is one of the tiniest IEMs at above $3k, but heavy. For a lot of people, that means they are constantly being pulled out of their ears – a very frustrating feeling. I really didn’t have that issue with the Spinfit W1s, but since a good seal is important to sound quality, I can understand how that would be super annoying. Other than the weight, the Xe6 are very comfortable due to their small size, which is pretty comparable to…every 64 Audio IEM ever since they’re all basically the same size/shape. Again, the Rn6 fixed this issue with an aluminum shell that cut down on weight, making them one of the most comfortable TOTL IEMs out there.

Xe6 Back.jpg


Check out the below. I’m comparing the Xe6 to the Trifecta since I have both on my desk, and I’ve added in the Rn6 FRG as well since I got it after the Xe6 was already out the door. The Trifecta and the Xe6 are not too far off with casual listening and it’s only when critically listening that you can start to pick apart the differences here. Obviously, the Xe6 has more bass, and what the FRG can’t show is the Kinetic Bass response since that speaker sits outside the microphone on the Xe6. So, just imagine that the sub-bass line is closer to 75 than 65 and you’ll get the idea of what the Xe6 really sounds like. Other than that, their lows are pretty similar, with the Xe6 a bit more pronounced. The Trifecta’s upper-mids and highs are almost the exact opposite of the Xe6 and where the Xe6 has pretty neutral highs, the Trifecta looks like a Colorado mountain range. They almost dip and peak in exact opposite places as well. The tests below will attempt to highlight what those differences sound like.

Xe6 Rn6 Trifecta.png

I am powering both off of my HiBy RS8 on the A/B amp (class A doesn’t seem to make much of a difference on IEMs) on Medium gain at around ~38/100 volume. The Trifecta is even easier to power at around 30/100 – both are more efficient than most IEMs, including the cheaper ones. I’m using the 4.4mm balanced port on the HiBy with the stock cables from both. The Xe6 does benefit from an increase in volume, providing a bit more voltage to the drivers. 4/10 points here - it's already been improved upon.

Lows (15/20):

I’m starting off with the Mid-bass/Sub-bass test I’m using David Guetta’s “I’m Good (Blue).” Damn, that’s some hard-hitting mid-bass, though I can hear that rattle that I get here from bassier IEMs on this song. The sub-bass is intense and gives me that breathtaking feeling I love from bassier headphones - this reminds me a bit of the Aroma Thunder here. While I don’t like that extra rattle (which usually happens on DD bass), and my highest-scoring bass headphones don’t usually have any of it (Rn6), I really enjoy the impact and sub-bass rumble that these provide. It’s definitely a trade-off you either like or don’t like – personally, I don’t want my headphones to sound like a Honda Civic with 10” subs in the back. 8/10 points here - if it weren’t for the rattle, which I only hear if I’m listening for it, these would be a 10.

Up next is Demon Hunter’s “I Am A Stone,” which I use to test whether the bass is too strong and overwhelms the mids as that is just as important as how strong/good the bass is. The bass here never overwhelms the mids and prevents you from hearing them, but it definitely can take away from the forward focus of the mids, which should be the primary focus with this song. The bass should be in the background here, but it’s often equal to the mids. So, it can bleed into the mids more than it should. 7/10 points here.

Mids (16/20):

Weaving The Fate’s “The Fall” is my test song for clean/dirty guitars and vocals with background instruments to see how clearly the vocals can be heard. Ooh, nice intro clean guitars, with a massive soundstage. The distorted guitars also sound detailed with the high-hats and drums still coming through clearly. The bass guitar can be heard clearly, but it doesn’t overwhelm the vocals. The cymbals don’t get overwhelmed in here and I can appreciate how clean everything is represented, especially on a song that can be overwhelming on cheaper IEMs (and some not cheaper). The guitars can still be heard, but they do feel more in the background than I’d really like in a perfect world. That’s my only complaint here and I really appreciate that there’s no sibilance or sharpness either, which can show up on this song with some IEMs (Trifecta), so 5/6 points.

Staind’s “Something to Remind You” has clean electric guitars and wonderful vocals – this song tests vocal quality and background noise. The guitars are not in the background here at all – they sound really nice with excellent layering and separation while you can clearly hear the detail of the fingers running across the strings in the background on the left side. There are very detailed and full-bodied guitars here and nothing feels distant or thin. The vocals are crisp while maintaining a full presence and focus in the foreground. The bass guitar can hit pretty hard toward the middle of the song, even occasionally overwhelming the mids, but it’s not really noticeable unless you’re looking for it. There’s no unwanted distortion or unpleasantness of any kind here and the Xe6 earns 6/7 points here.

To test classical instruments in the mids, I’m using The Piano Guys' “Code Name Vivaldi.” The intro cello sounds great and of course, the intro cello-bass is epic. That epic bass really drowns out the mid-strings though and makes the piano hard to hear when the piano is quieter, and the bass-cello is louder. The same goes for the mid-cello, it can get drowned out when the bass-cello is playing at its loudest. While that is a letdown (and admittedly an ongoing theme with these IEMs), the overall song is filled with emotion, power, and clarity. This is why the Rn6 was created - because this bass bleed was the biggest complaint with these IEMs. 5/7 points here.

Highs (16/20):

To test sibilance on headphones I use Panic! At The Disco’s “High Hopes.” There is some sibilance here, but it’s nowhere as bad as the Trifecta, which was brutal. That’s one of those peaks on the Trifecta chart that the Xe6 dips at instead. Overall, this isn’t perfect, but it’s a little above average. 5/7 points here – the rest of the song sounds great.

Dream Theater’s “The Alien,” is the highs test song I use to see if the cymbals/high-hats/snare drum can be clearly heard and distinguished from the rest of the music (also good for instrument separation.) Surprisingly, the highs can be heard quite clearly over the mids here. It’s not quite up to Trifecta or VxV level, but still really good. You can hear individual cymbal strikes - all while the mids and high-mids still come through well. Yeah, the bass and drums can overwhelm a little at times, but we’ve hit on that on previous songs, so I won’t double tap here – some really impressive highs considering. 6/7 points.

Michelle McLaughlin’s “Across The Burren” is another of my favorite highs/sharpness test songs as it can easily sound painful on some headphones. There’s a touch of sharpness here, but it’s still far better than some of the sharpest IEMs I’ve heard. 5/7 points – still a good showing from FiR.

Soundstage/Instrument Separation/Imaging (10/10):

I use MGMT’s “Time to Pretend” to test soundstage, instrument separation, and imaging. Yeah, you already guessed the Xe6 is going to do well here. Instrument separation is fantastic as long as the bass isn’t going super hard – then it can get a bit blurry (3/3 points). The soundstage feels huge, like Mentor level huge (3/3). Lastly, the imaging is very good also – you really get that 3D feeling from the Xe6, none of this forward 180 degrees feeling like you can get from the Ronin and several other IEMs. There is true immersion on the Xe6, especially with the kinetic bass, which you can really feel. It’s equal to the Multiverse Mentor (at least to me, others disagree – go read their reviews if you care) here and earns the full 10 points.


I think the comparison here to the Trifecta is pretty easy if you’ve read my Trifecta review. The Xe6 has significantly more bass overall, though both can overwhelm a bit on the lows (nothing like tha Fatfreq mini though, ugh). If you want more bass, with less resolution, get the Xe6, if you want cleaner, more detailed bass, grab the Trifecta. You can really feel the bass on the Xe6 though, which is why it’s called kinetic bass – it’s a much more concert/club-like experience than the Trifecta. Both do pretty well with mids, but the Trifecta is the clear winner there with a much more forward mids presence that doesn’t get overwhelmed (it still has one of the highest mids scores I’ve ever given). For highs, it’s a challenge, if you’re sibilance sensitive like me, get the Xe6 as long as you’re cool with the bass. If you’re not sibilance sensitive, and you really love insane highs quality, get the Trifecta, they have some of the best highs I’ve ever heard with no sharpness. Yeah, like all things in life, it’s a trade-off. I prefer the Trifecta’s bass and mids, but I prefer the Xe6’s highs while it bass and mids aren’t far behind the Trifecta’s. You do you Boo.

Oh, yeah, you probably want to know how it compares to the Rn6 huh? OK. The Rn6 has less bass, a MUCH better cable, a better build quality and finish, a Red module (which most people like the most), better mids and highs, no bass bleed, a smaller kinetic bass hole, and is one of the most balanced IEMs I’ve ever heard. It’s probably the highest-scoring IEM I’ve ever reviewed. BUT, and this is a big but (heh), it loses the emotional connection you get from the Xe6. So yeah, the Rn6 is cheaper, limited to 300 units, better built with a really nice cable and an excellent sound – basically perfect – but less special at the same time. *Shrug* get whichever one matches what YOU’RE looking for. Or, get the Trifecta which can do all of the things pretty darn well.

Xe6 Front.jpg


As many previous reviewers have mentioned, the Xe6 is a purely emotional experience. It’s not meant to be broken down and analyzed (like I just did). It’s meant to be listened to and enjoyed with its insanely large soundstage and immersive feeling. Its score can’t reflect how the overall presentation can make you feel – and frankly, it doesn’t deserve a score this low, but that’s how it breaks out when we dissect each individual piece instead of looking at the overall presentation. Yeah, it’s not quite a mids-focused set like the Ronin and Trifecta, and yeah, the lows can bleed into the mids a bit (a lot). But, with really well-balanced highs (that avoid most of the sibilance), fantastic detail and resolution throughout the entire frequency band, and some very compelling bass response - the Xe6 is one of those IEMs that will keep you coming back for more time and time again. There’s something about Xenon.

Headphone Scoring (v3):
Accessories / Earpads / Eartips (10 pts):
Cable (10 pts):
Build Quality/ Design / Comfort (10 pts):
Lows (20 pts):
Mids (20 pts):
Highs (20 pts):
Soundstage / Instrument Separation / Imaging (10 pts):
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John Massaria
John Massaria
You are amazing thanks for this review !
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One of the best reviews I read on this site since I joined. Thank you for this.
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Headphoneus Supremus
Pros: -amazing bass performance
-kinetic DD rumble, grunt, resonance and vibrancy
-sub and mid bass layering
-physical bass sensition
-plenty of lower mids (warm and thick)
-smooth cohesive balanced W shape
-engaging dynamic rendering
-natural and densely rich timbre
-supremely enjoyable male and female vocal (wide and thick)
-excellent tone-timbre for sax, piano, cello, contrabass, violin
-warm but not dark mids
-wide and tall holographic spatiality
-snappy EST highs
-velvelty treble
-fun, engaging yet versatile and life like musicality
Cons: -not end word in term of technical performance
-not the best bass separation and definition (lack of texture)
-a hint foggy mid range (softed definition edge, surely due to open BA design)
-not very clean treble (again open BA design)
-EST tend to pick background noise
-EST tend to stole the show of other micro details or percussions
-EST go faster and add a sens of speed that not always match slower DD and BA presentation
-the IEM sensitivity isn't stated (and seem high)
-my car doesn't worth 4K$ so i can't sell it to buy those


TONALITY: 9.2/10
SOUND VALUE: Cannot apply
(for me technical benefit is average but musical benefit is very high)

Just a little introduction to my audiophile journey and experience.
I've done audio review for about 7 years now, with an insatiable curiosity about sound value in all price range. But I didn't limit myself to high sound benefit return since musicality have no price logic. In fact, I go from Westone ES2 custom IEM to budget chinese IEM, then try or review more than 300 earphones in all price range including Kinera Urd, Hifiman RE2000, Final A8000, UM Mext, Aroma Thunder, Sony Z1R, Shure KSE1500, 64audio Nio, Campfire Andromeda, Dita Fealty-Fidelity etc.
Yes, i'm crazy. But for an headfier, I think im temperate in fact.
I tend to favor musical balance over in-your-face technical performance, yet, when I go into critical listening I separate both for analyze. I'm very sensitive to timbre and tone naturalness and tend to dislike thin sounding IEM, but again, since I listen to very wide range of music from classical to jazz to Soul, R&B, Rock, Rap and stuffs, thin mids aren't really an issue for lot of genre or anything without acoustic instrument or vocal.
I'm know to be not easily impress by IEM.
Sure, when we go into kilobucks one it tend to be less underwhelming than sub-100$ cheapies, but their very bad one like the Dita Fealty for ex, I don't like Shure KSE1500 at all too since it's a prime example of in-your-face all technical sound with thin timbre.
I love Nio, Z1R, A8000 and to some extend the Mext.

And did I love the Fir Audio Xenon 6 too? Well, we will see in this review!

Let's begin by saying the Xe6 are a loan and I have zero obligation to review them. A Canadian fellow with way more money than me loan me this for 3 weeks. I remember how they arrive, I was doing a ''reviewer walk'' with the Aroma Thunder, planning to find and keep critical listening momentum to finaly complete the review. I can easily get distract with other IEMs when an IEM I need to review don't truely mesmerize me, which was the case with the Thunder. So, it was forced work we can say, i need to say focus but decide to do a stop at post office wishing their nothing to distract me. But the Fir Xenon 6 was there.
All the way back to home I was repeating myself: Eric, don't be frail, stay focus on your critical listening impressions and don't listen to Xenon 6 before at least writing the audio impression you pile up in your head. Be brave, be a man, be mature!
Then very first thing I do entering my home is throwing away the Thunder, runing into my bedroom like a kid back from halloween with it's candies bag and put the Xe6 in my ears. I never pull them off until I was too sleepy at 2am. And report my Aroma Thunder review for days and days.
C'est la vie!

In fact, I didn't even know the price of those nor that much about Fir Audio company, to be honnest, I even have prejudice about this company even if as an artist, I do enjoy their cartoon. Then i begin to read and understand the staff were working for 64audio. And I love 64audio. Then I read about kinetic bass and other tech they use, some taken from 64audio other exclusive to them and I was like: OK, it's no amateur audio company, that's legit audio engineer with a unique vision!

And then I see the price and barely fall from my chair. 4000$! OK! 2 times pricier than my Final A8000. But hey, it have more drivers and exotic tech.

Their no doubt that what fascinate me at very first listen was the bass experience like no other I ever heard. It was out of my head and in my head but pounding on my skin too, it was physical and musical and technicaly very competent in term of sub bass rumble and mid bass punch that doesn't melt togheter yet have the natural warmth to it. But then the vocal come and go above this bass and whole spatiality was feeling so open, holographic and immersive that I know it was a love at first sight, i mean listen. This make me sad because I can't afford those, I would sincerly love to tell you I hate the Xenon 6 but I don't lie. But let say this review is not about sound value, just forget about this paradigm, it can't be apply at IEM above 2000$, just can't. Let's say musical benefit return is high, but out of money context. Based on this premisse. We can begin the more serious review part.



The Xenon 6 is a tribrid earphone with 6 driver per side: 1 kinetic dynamic driver for lower bass, 4 open balanced armature for mid bass (1), mid range (2) and treble (1) and 1 electrostatic driver for ultra highs.
It use these 4 patented technology:
A hybrid conduction technology that takes the IEM sound experience to a whole new level. Kinetic Bass is a bass you can feel.

note: unique genius tech. this add sens of bass openess and depth as well as physical vibrance to bass punch and rumble. for proper effect, it need to be near your inner ears bone.

A pressure relief system that vents pressures that build up in a sealed ear canal. Greatly reducing listener fatigue so you can hear more and listen longer.

note: this indeed permit to have less loudness pressure, its used with near all IEM and just call venting, with Fir, it's used for tuning module too that will inflict on sens of openess and resonance.
Open drivers with no sound tubes that radiate sound directly into the Sound Reactor which results in a much larger sound stage.

note: this is as well a rather common BA implementation, which have pros and cons, the pro is that it tend to avoid tubed BA shoutyness and agressivity and make it sound more wide in sound layers presentation, but it slow the attack speed and blur definition edge a bit, so we can say it's relaxed BA presentation.

Proprietary technologies that provide industry leading durability and serviceability of our in-ear monitor products.

note: OK, i think Fir audio just love to patent everything....but housing is indeed very sturdy and durable.



The Xenon 6 are one of a kind when it come to construction and design. It's made of thick machined stainless stell that seem extremely sturdy, and the back plate is made of sapphire glass that isn't easy to scratch, which again promise rather good long term durability.
The shape is not the most organic, but don't have hard angle to it that create discomfort, as well, it's not very big, but the metal material used is quite heavy, so using a cable with ear hook is mandatory with those. Anyway, i never encounter discomfort even afte rlong listening session (8H non stop daily).
The nozzle is long and permit deep enough insertion, but ear tips holder isn't very secure so some ear tips tend to slip, this is to be noted for those wanting to use short wide bore for example.
The 2pin connector aren't embeded in the shell for secure connection, it's nitpicky, but i think it would have been better.
It seem the connection can become looser with time, but this is inherent to 2pin connection made of plastic.


On the top of housing their a little screw, it's for Atom XS modular tuning. You need a kind of small allen key to unscrew and change it, this isn't very user friendly and one thing to note is that after some use, the screw module will loose their paint, making it near impossible to discern between each other. This is a concern to be noted (and solved).


The cable included is nice enough, nothing mind blowing for a 4000$ IEM, but not a ''joke cable'' like some included with high end IEM like Aroma Thunder or Hifiman RE2000. It's a strudy 8 cores cable, its not specify what type, but surely oxygen free silver plated. As well, it's 4.4mm balanced plug.

Since those are loaner unit from a friend, I don't have whole package, but it seem minimal anyway.


Let's begin by saying this whole sound review is based on the Gold tuning module, which give an extra 2db bass boost and add slight hint of warmth. Whatever the tuning module, I don't think the Xenon 6 will go bass light, I mean, it's all about the kinetic bass + BA woofer here, and why make sugar less something that sound so sweet and yummy right?

So, as a whole, the Xenon 6 tonality can be summarize as a warm W shape that offer proper dynamic and presence for each main part of sound spectrum. It's bassy, lushy and snappy. Its a balanced basshead set with thick yet well layered and holographic macro presentation. It's not neutral nor boring sounding, it's not analytical nor particularly impressive technicaly, the wow effect belong somewhere else with the Xenon 6, and yes, it begin with this mind buggling bass performance and flavor.

The bass of Xe6 was a big crush at first listen for me, and the full magic of matching a balanced armature woofer for mid bass with a big kinetic Dynamic driver for sub bass is certainly well achieve due to the cohesive, flexible and highly engaging result we are spoil with. This kind of bass isn't possible with fully closed acoustic design since reverberance boost the rumble loudness pressure which is not an issue with the Xe6.
Exotic in dynamic rendering and natural in tone and timbre, the sub bass and mid bass are both thick and superbly layered, it's not about boost in presence texture and definition but full physicality of both kick drum and bass line or kick natural decay you will get.
I want to talk about this ''physical oomph'' kinetic bass give, where we can finally feel the inner vibration of this special euphonic boom.
Its layered over the sub bass, it's a bone conductive impact that can't be mimic in other way than from a speaker moving air outside of your head. This is the magic here that is so freakin addictive.
It tend to magnify overal sens of spatiality by adding a ''4th dimension'' to it too.
So when the kick hit in loudness and presence, it have an extra body weight that will hit your temple, it can go gently to more energic depending of volume you listen to, thats another very important aspect of Kinetic Bass DD that perhaps haven't been underline enough, I dont think people listening at super low volume will get same physical rumble and oomph experience.
How near of your temple is the Xe6 will inflict too on this, in 2 way, cleanliness and density of impact, it can go more open to more concentrate.
Now, this sub bass presentation is all but just about resonance trick too, since it's dense and vibrant. For cello or contrabass it will add the bodied grunt we get in live concert when the player hit lower note with it's bow, while for electric bass it will present each note in all fullness, with natural but a bit softed tone. We have a bit of warmth coloring that avoid over analytical texturing of instrument, but it doesn't feel lacking. As well, I would not say the linear space between instruments is the widest, in fact, bass to lower mids transition is made in a thickly layered way, it's not made with a ''silence dip'' for crisp separation.
It's luscious gourmand bass, with fast round warm kick and beefy holographic sub bass that dig deeper than you ever wish and induce a relaxed headbanging experience free of loudness fatigue or too radical basshead IEM.
The dynamic presentation not only permit to offer full sounding male and female vocal, or add density and naturalness to saxophone, bassoon and piano, but excell with genre like Jazz, electronic, Soul, R&B. The music genre that do a bit less well will be metal or very fast rock that need extreme speed and clean definition. But in fact, I would not consider the Xe6 a good choice for intense critical listener seeking true high fidelity presentation since here it's all about a musical vision, and one that seem carved for my very ears.
The kinetic bass experience is physical, since you feel the rumble on your temple, but the magic here is that it feel beefy and well rounded too and as with whole Xe6 tonality, it magnify tone and timbre richness before presence grain, texture and definition. Believe me: their no other IEM that deliver this bass experience, and once you taste it, you can't forget about it.


I rave so much about the bass, not only in this review but everywhere, but does it mean the mid range is subdued or underwhelming?
Not at all, quite the opposite in fact unless you seek for clean neutral presentation or highest transparency and resolution possible since here it's all about body and tone lushness pleasure. Firstly, it seem lot of audio lover tend to forget about lower mid range, which is often non existent in lot of IEM, harman target being prime example of that. Presence of instrument being more about lower treble region, we have way too much anemic mids that hook our mind but left our hearth cold. Xenon 6 follow the opposite of this approach, while not lacking in minimal presence definition and texture, it tend to magnify the density and tactility of mid range instrument like piano, saxophone, violin or vocal. We have heavy note weight, we have wide and lush vocal presence with beautiful lower range coloring that magnify sens of air vibrancy within those instrument and soften a bit the hard edge of presence other earphones will choose to boost to the cost of sibilance or shoutyness.
Smooth, creamy and breathy are the vocal and it might be among the most beautiful I've ever heard. Again ,we have an holographic layering to main instrument which are widely stretched in center stage and so close to you it tend to embrace you like a cocoon.
This isn't the type of mid range that will not make lipse noise invasive at all, nor the most energic in attack bite too, it tend to put the fundamental of instrument as the main tone focus, so everything sound melodious and effotless in musicality.
But it's a bit warm too, so resolution is darken by that and again I feel the Xenon 6 do better for slow music or not too busy track, for classical symphony, you will struggle to perceive all instruments, especially in loud excited passage.
But for chamber orchestra, the result might blow your mind too, since all piano, cello and strings will offer fullness of presence, natural timbre and dynamic heavy weight. You will be in the middle of them, part of an holographic euphony like no other free of any displeasant harshness or treble grain.

Then there come the treble which have it's EST driver as the star of the show we can say, because it's the one responsible for extra air, fast snap and beautifull brillance. While low and mid treble is deal with open balanced armature that offer thick dense highs, the EST is perhaps only tonal sharpness of the Xe6. Sure, it feel a hint detached but not to the point of feeling wonky or out of place, it complete the holographic sound experience that the mix with open kinetic driver permit and wide open BAs mid range.
So the treble is rich in velvety sound layers and snappy micro details or percussions, have a sens of presence thickness and fast spot on treble spice. Yet, i would be hard pressed to call the highs clean or highly resoled, while calling it plain dark too, which isn't the case. The attention of listening isn't hooked by the energic attack of EST, which doesn't always pick up whole range of percussions so this can affect proper pace of macro presentation, in the sens some percussions will sound more tamed in loudness and snap than other. Again, with more simple music, this isn't an issue at all and in fact even with a problematic album like ''Art in Motion'' from Aki Rissanen where the percussions timing is very important and drummer use wide range of percussions pitch with different sustain in resonance, it doesn't annoy me unless I go into intense critical listening like right now. But this can be in fact pleasant too since at least we do have this percussions snap that are so addictive and engaging, and depending of complexity of drumming, it tend to fit perfectly any kick-snare-percussions rendering, add a vocal in the middle and bass line and you got the whole joyfull head shaing musicality you dream off.
Because everything have weight or airy tactility with the Xe6, even the treble, nothing sound too light or thin. The open balanced armature offer effortless and fatigue free violin and eletric guitar, high pitch of saxophone sound suddenly full in harmonic, not just about high pitch concentration. You don't have any BA timbre, fuzzyness or metallic sheen (appart from EST with well, metallic instrument).
And I was happy to be able to appreciate the clavichord of Pierre Hantai with the Xe6, even if not perfectly restitute, the speedy playing was well timed and brilliant enough even if short on decay and natural resonance and not the sharpest in note definition. I can say the same for Harp, but when low and highs harmonic are play fastly some resonance bloom can unbalance the rendering. In fact, it just underline the peculiar mix of tamed low and mid treble edge and sharper, cleaner and crisper upper highs.
All in all, I could just have write this: smooth but sparkly treble.

The spatial presentation is quite incredible with the Xe6, if you are familiar with term ''holographic'' it's the first word that come to my mind, but a stretched multi-dimension one. The headroom is very wide and tall, and do have a sens of depth but not a clean or very airy one, yet, we do have extra stereo openess from EST driver that add deth, not just in center stage since nothing sound distant or far from you with the Xe6, yet it's very spacious. It's really like having 5.1 surround speakers around you, at about 1 meter distance and a sub woofer in the back of your head.

But this doesn't mean you get the most accurate imaging, because for monitoring instrument you need to be position at some distance from the band, here your in the middle of it so you are literally into the mid range and have stereo separation for treble and bass. When it's a track without bass rumble or resonance, it will be easier to pin point instrument placement but all in all the Xe6 are no master of static instrument placement.


While the Xe6 impedance of 28ohm is stated, ackwardly the sensitivity isn't. I'm not sure to understand the legitimicy to omit this important information, but my guess is that sentivity is rather high, perhaps between 120 and 125db to give a vague (and safe) approximation. I conclude this because these are very easy to drive and even benefit from low gain from both Moondrop 4.4m and Hiby RS6, at high gain it will tend to pick up noise and be more agressive in dynamic, overly excited we can say, which affect negatively overall smoothness of the tonality.
So while I would not say they benefit from amping power, I do think pairing the Xe6 with clean and smooth audio source is important for making them scale up, low output impedance and low current gain is suggested. But this doesn't mean they pair well with dead flat amp like the SMSL SH9, which seem to damp dynamic of bass rendering making the Xe6 sound near cold neutral, which is a infamy!
Pairing isn't always previsible in result and my favorite one wasn't with most expensive DAP like Questyle QP2R or Hiby RS6, nope, it was with the humble dongle Moondrop Dawn 4.4 which seem to add sens of openess, doesn't have bass roll off and embrace the W shape dynamic beautifully.

Now, the ear tips too are important to achieve full sound experience of the Xe6, KBear 07 was my choice to get most open and full bodied tonality, as well as having the proper fit to have kinetic bass port near my temple, this is important to get proper bass sensation.

Cable to a less extend will inflict on dynamic rendering and how clean can go the Xe6, stock cable isn't bad but seem to make the dynamic more in your face, adding hint of loudness gain, so I choose the Tri Grace S 6N litz copper silver plated cable for a slightly crisper result with improved layering articulation and overall more organic tonality with lively effortless dynamic.


VS UM MEXT (1DD+4BA+1BC-1100$)

The Mext tribrid don't use Bone conduction transmission for purpose at all, it's a wide range that cover 200hz to 7000hz region by adding presence details and magnifying sens of resolution and transparency. So, firstly, they sound more vivid and crisp, we can say more neutral even if quite bassy. We are sure more invade with micro details as well as a more analytical sens of spatiality. Everything sound cleaner, yet thinner too. Everything but bass, which is in fact warmest part of Mext tonality, and it feel sloppy and lacking well rounded definition which the Xe6 offer, as well it's less punchy and we struggle to discern kick and bass line dynamic way more than Xe6, so more U shape bass in that regard. Then the mids is all about presence and have colder timbre, female vocal are more stick in your head, less wide and dense in presence and more agressive in loudness so here you will hear those lipsy details if you care about them unlike the warm thicker lusher mid range of Xe6.
The treble is the part Xe6 feel notably inferior and darker, as said, we have more details but attack speed, control and snap is better with the Mext too. Definition and texture of instrument is edgier and cleaner, highs are more open and airy, attack lead of violin is more abrasive and realist and unlike with Xe6, we will never confound by error cello and violin.
Spatiality wise, the Xe6 is slighlty wider, notably taller but less deep and clean than the Mext. Imaging isn't really the highlight of these so it's no surprise the Mext surpass them in that regard, layering is more transparent, instrument separation is cleaner and sharper and positioning more accurate.

All in all, I would say the UM Mext is superior technicaly in every department but bass while it offer a colder more analytical musicality that doesn't trigger any emotional response in me, unlike the overwhelming one of the Xenon 6.

VS FINAL A8000 (1x pure beryllium DD-2000$):

Ok, this is a big deal since these are among my fav IEM ever...yet, the tonality have nothing to do with the Xenon 6 here, even less so than the Mext. So if the Xe6 are warm W shape, the A8K are vivid bright W shape with less boosted bass and mids and more focus and edgy treble. Here, it's not the bass of A8K that wake you up but its crazy fast and talented treble only a great quality pure beryllium driver can offer. Listening to same music with the A8K make you feel it play in higher BPM and if the drivers of Xe6 were trying to run against it, only the EST will go to finish line.
So the bass is more textured and less boomy and euphonic thant Xe6, it's less heavy in punch and less dense in timbre, the rumble is thinner too and not as sustain, separation with mids is cleaner, attack is faster and tighter and overal lower instrument resolution is better define.
Mids are brighter and thinner and more agressive and prompt to sibilance with A8K, it sound more open due to more recessed center stage and offer way crisper resolution. Definition of each instrument is edgier and clearer, and even if greatly textured, transparency of instruments are higher with A8K.
The the treble which is star of the show of A8K certainly put to shame the Xe6 since here we have more sparkle and natural decay than the Mext and perfect mix of highs fullness and crunchyness. These sure permit to deal better with fast busy track as well as offering proper bite to violin or electric guitar, so for metal head the A8000 is a better bet unless treble sensitive.
Spatiality is similar in wideness but inch taller with the Xe6, again, it lack the deepness of A8K. Imaging is intensely superior with A8K both in accuracy and proper space between instrument as well as greater amount of sound layers that can coexist at same time.

All in all, I will not sell the A8K to get the Xe6, and in fact would love to have both due to the fact they complement each other perfectly. But the mind blown here is the fact a single dynamic driver can offer superior technical performance than a 4000$ tribrid.


Ok, we are into big boi battle here and well, only thing these 2 have in common is the overall natural and laiback musicality, presented in a very different manner and tonal balance.
The Thunder is more neutral to mid centric with sub bass boost while Xe6 is more bassy L shape to warm W shape. What hit first is how more closed and intimate sound the Thunder compared to wider more open and holographic sounding Xe6.
Then it’s the bass, which is more boosted in punch, deeper in rumble and extension and more physical with the Xe6 (especially with bass tuning module), the rumble is more sustain thich and vibrant, it feel better layered too, the kinetic DD make us think their 2DD in there, bypassing limit of lower end acoustic law. With Thunder, kick and sub bass line can feel on same level and lack proper articulation difference in dynamism, while the Xe6 can offer both full bodied bass line and kick punch without canceling each other dynamism.
The mids are notably fuller sounding and more natural, vocal blossom in a wide way and feel more compressed and artificial with the Thunder. Timbre is denser and better in timbral balance fullness. Its not as detailed and transparent, yet, sound layer have more space for proper articulation.We can say Focus mode is slightly more similar in tonality, but suddenly darker, so again, its Harmonic mode i compare too here. Treble is the part we technical performance is superior with the Thunder, yet, less open and musical as well as less sparkly. EST offer sharper brilliance and more decay to sparkle. When it come to lower treble, it’s smoother too but fuller, so violin sound more natural and bodied, lusher than Thunder. Overall treble is thinner and colder with the Thunder too.
Spatiality is night and day difference here, the Xenon 6 is way way wider and taller, more holographic and center stage isn’t as recessed so it’s a bit less deep than Thunder that have a ”tunnel vision” spatiality.
Imaging is more realist with the Xe6 but your even more in middle of music, it’s more 3D and holographic, while it feel more static with extra highs positioning for the Thunder.

All in all, the Fir Xe6 sound more musical and less technical than the Thunder, offer more mids body and lush presence as well as more physical and punchy bass experience and smoother but sparklier treble. Their no doubt the musicality is way more engaging and emotional with Xe6 and could justify an impulsive car selling to enjoy this sound experience, while for the Thunder I will not even sale my rusted old bike.



The Fir Audio Xe6 offer a warm W shape signature, that extract all main aspects of music very well, not over boosting texture or details and instead favoring fullness and naturalness of tone and timbre, without going dark due to a quite snappy EST.

Not only the bass unique dynamic presentation is fantastic, but both male and Female vocal are incredible too, perhaps my favorite from all IEM i've tested yet, they are addictively dense-wide-lushly-textured enough with creamy but not dark upper mids.

The Fir Xenon 6 isn't about trying to achieve an overly serious and austere high fidelity musicality that will put you distant from your favorite musician, instead it put the listener right in the middle of the band, well setted on a sub woofer.
Sure the price tag is high here, but when we know richer people can pay thousands of dollars for a fancy pizza with foie gras and truffle on it, I do think such a listening pleasure isn't that crazily overpriced, it's just out of common sound value concept were technical performance and ultra high resolution is main concern.
Yet, I do think Fir Audio could go all in basshead IEM one day and push the kinetic DD tech to it's paroxysm, and it would be a wise idea to make it more affordable for the mass, which love bass too. And vocal.
Until then, time for me to go stole a bank and get my own Xe6 pair!

Highly recommended (if you can afford it)


For more diversify audio product review, give a look to my website here:
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New Head-Fier
Pros: - sound quality
- gorgeous design
- on-the-go tuning (almost on-the-go)
Cons: - unexpected tuning for such price
- not quite comfortable process of filters changing
- they deserve a better cable
Just want to say a few words about myself. I have been a reviewer since 2019. It's my first English version of the text, so just don't blame me to much. I have more than hundred texts on era-in-ear's blog but thank to one kind man I decided to try sharing it with non-Ukrainian speaking public. If it finds some interest, I will publish some other texts, not only about actual models or only top-segment.


Fir Audio Xenon 6 are the headphones that can surprise. Once I had a whole honeymoon with Fir Audio products in a past life, before the war forced me to leave my audiophile cavern. They have just appeared on the shelves of our stores, and it was necessary not just to talk about "deep layers of low-frequency and extended highs", but to present the brand to people in Ukraine. Moreover, it is not alien to the Ukrainian heart ear. You remember that both Fir Audio and 64 Audio are creations of the Bilonozko brothers. At that time, 5 models with which we "discovered" Fir Audio for ourselves had a different, attractive, tasty sound, while there was no "sound doctrine" according to which all models would sound with an adjustment for the budget. But the top and pre-top M5 and M4 more or less had certain similar features and I liked both very much. Therefore, for the Xenon 6, I expected a continuation of the genetic code of both top models. And I have never misled myself so strongly and stubbornly.

Relatively recently, Fir Audio presented a whole new line. If the previous one had a very laconic and mysterious name "M" (Moriarty?), with the exception of VxV (V - vendetta?), then the new one received the pathetic name Frontier - edge, border. Almost Rubicon. But this name is already occupied by elegant acoustics from Dali. The Frontier line includes a total of three models: Neon 4, Krypton 5, and our reviewed one, Xenon 6. As you might have guessed, the number in the name is related somehow to the number of emitters.

Perhaps this text will start another "thematic" cycle, so we do not reject this possibility. Like any other.


The packaging format reminds everyone of the M-line. This is a small, especially considering the price, box hidden in a yellow super cover. It shows the manufacturer's logo and the inside of the headphones. Purely schematic, with a clear emphasis on one of the main features of the model. "Xe6" is the manufacturer's abbreviated name for the model. Like the rest of the representatives of the Frontier line, by the first two letters and the number of the index. Ne, Kr, Xe… It feels like I'm back in high school chemistry class. What is the valency of krypton?


In the main black drawer, as usual since the M-era, there are the headphones themselves on the housing, a cable, 5 pairs of nozzles (3 silicone single-flange, 1 double-flange and 1 foam), an organizer for filters, a tool for working with them, documentation and... a chevron of Pluto's territorial defense space forces. The strangest accessory that I have come across so far. Even Dunu Luna can't beat them here, where there was simply more than needed. VxV used to have a set of cool stickers from Firi that would look cool on a laptop, and this patch requires at least a leather jacket, an electric scooter bike and a cup of almond latte.


In terms of ergonomics, the cable is excellent, soft, without a microphone effect, does not harden. The 8 copper conductors are tightly braided and are terminated with classic 2-pin connectors (thank the audiophile gods that the Frontier hasn't proprietary connectors) and straight Pentaconn jack. Of course, the cable is nice, but these headphones are begging for some kind of silver or a hybrid with its participation.

3 pairs of filters are in the set. I will talk about them in the "technological" section, but be careful if you have thick fingers and poor eyesight. You will suffer.


The chassis of the headphones is made of stainless steel, accordingly, they are quite heavy - 14 grams. Moreover, the cases are covered with gold, so this heaviness is very pleasant to the touch and visually, taking into account the shine of the precious metal. I'm not a big fan of gold in my ears, but Xenon 6 look really luxurious. I can't argue here. I like it, I don't like it - it's a matter of taste. Someone will definitely like them. And someone will not.

The faceplates are decorated with an insert made of cross-section of carbon fibers with the addition of gold foil. All this luxury is protected by sapphire glass, by the way. The left earpiece has as a final touch the name of the model, abbreviated, i.e. Xe6, the right one has a logo in the form of rabbit ears. How is it possible being without them?

Next to the 2-pin connector we see a micro-screw. The possibility of replacing individual components of the case, such as, for example, the connector for connecting the cable, has been implemented here. Also on the soundtube in front of the filter mesh, we can see the filter attachment lock. It can also be replaced in case of damage or permanent contamination.


On the upper side of the case there is a slot for fitting the Atom filter, which in the Fir Audio Xenon 6 and in the entire Frontier line received the index XS. Yes, he did lose a few sizes. If you compare it with previous models, it can be equated to the transition from XXXXXL to XS. But in terms of convenience, the old design is not that far above - it is somewhere in the mesosphere.

Filters have something that looks like a thread, but it's not there to do what a thread does on every other product in the universe. Therefore, when changing filters, you will have to have a threesome with a filter and a bit, which the manufacturer carefully put in the box with accessories. Sony's business model is to sell you a console below cost, then rip you off on game purchases and subscriptions. The Fir Audio model is to add a mandatory replaceable component to super-expensive headphones, which with a high probability will be lost. Although, something tells me that playing with filters will be over within the first week. Because I quickly found the most acceptable one for myself. Regarding their properties - further.

There is a huge hole on the inner side of the headphone. In this "neckline" we see the reverse side of the dynamic emitter. No, it is not for beauty and showing off, such a solution has a purely technological motive. Xenon 6 implements Kinetic bass technology, which I will, of course, also talk about. The bottom line is that it requires closer contact between the emitter and your skull bones for it to work. This is what the "décolletage" provides. It looks interesting and unusual. By the way, Xenon 6 has the largest hole in the case, despite the same diameter of the driver itself.


As for ergonomics, everything is definitely good here, but there is a nuance. The headphones are small and sit perfectly in the ears, without creating discomfort, and given the work of the Atom technology, the comfort accompanies your hearing system as well. But the soundtube has such a length and diameter that some of my most used nozzles simply covered it and did not provide the necessary fixation and isolation. Instead, the Sony Hybrid sat in such a way that their narrow soundtube became wider and provided a normal tonal balance. After all, after selecting the nozzles, the ergonomics of Xenon 6 should suit you to the fullest. Xelastec Crystal also turned out to be quite suitable.


From reviews of the previous line, you probably understood that Fir Audio is a company that bets on technology. It is the refined and thoughtful solutions that allow the company to achieve both the sound signature and the level for which their models are known, in particular the charming M5. For those who are familiar with the company's products for the first time, I will talk about the technological features of Fir Audio models using the example of Xenon 6. And for the rest, I will simply remind and refresh their memory.

But first, briefly about specs. The headphones have a hybrid design and use 6 emitters of three types in their own acoustic system. One 10mm kinetic bass driver for woofer, one open armature driver also for woofer, a pair of similar open armatures for mid frequencies, one more for HF and one electrostatic driver for far HF. 6 emitters, 3 types. Everything is simple, relatively, but not. Not all. About it here, but below. The resistance of the headphones is 28 Ohms, the frequency range is 20 Hz - 20 kHz. The manufacturer does not specify the sensitivity, but it is, according to my observations, high. Of course, Fir Audio Xenon 6 will also play from some dongle, but the headphones will fully thank you for a good and, most importantly, powerful source.


So, what do we have inside? More precisely, not what, but how exactly everything is arranged there? I was talking about the relative intelligibility of the acoustic circuit. Relative - because 6 emitters have three different sound reproduction mechanisms. But they have one thing in common – they transmit sound in a classic way, that is, by creating air vibrations.

You have already understood that I am leading to bone conduction. So. "But there's no bone conduction driver?" - you will ask and be an audiophile of Schrödinger, that is, you are right and wrong at the same time. Xenon 6 implements Kinetic Bass technology. Its essence lies in the combination in the dynamic emitter of usual dynamos mechanics and the bone conduction driver. This is achieved in two ways. First, the speaker is located directly on the headphone body and it "gives" part of the kinetic energy of the dynamic system movement to the body. It interacts with the cartilages of the auricle, which, respectively, transmit the sound signal to the auditory ossicles (hammer, anvil, and stirrup). Secondly, there is a hole in the case itself, which I already mentioned. It allows the Kinetic Bass system to deliver more kinetic energy to the cartilage. This essentially turns the Xenon 6 into something similar to the Mext and Mest, but without a separate bone conduction driver.


But, for what? This is all to improve the listening experience. Manufacturers of hi-end headphones aim to recreate the experience of listening to full-size speaker systems. In particular, with the help of in-channel monitors, which, despite their modest size, have a whole variety of complex technologies in their fields. Kinetic Bass is designed to reproduce the feeling of being able to touch the "big" sound waves that you perceive with your body and bones, in particular with the help of Xenon 6. What, but they definitely do not lack tactility.


I also mentioned the filters. This is the good old well-known ATOM (Air Transferring Open Module) system. It is designed to relieve excess pressure that forms in the actually closed space of the ear canal. When the diaphragm of the acoustic driver reciprocates, the air mass, essentially closed in the chamber between the driver and the eardrum, creates excess pressure on the eardrum. As a result, in order to prevent overtiredness, the sensitivity of the auditory system decreases. You want to turn up the volume, and then more, and more, and more…

This leads to hearing impairment over a long distance. If not abused, the consequences will be less painful, but still undesirable - fatigue and the inability to spend a long time in headphones.

Instead, Fir Audio offers a system of ATOM filters that release excess pressure to the outside, reducing it inside the ear canal and, accordingly, reducing the impact on the eardrum.

In Xenon 6, the filter "shrunk" to the size of a match head. If the universal models of the M-line had a built-in internal non-removable filter, and the custom version had its external version, then in the Frontier line we have something in between. The filter is replaceable, there are three pairs, but in size it is somewhere on the same level as the non-removable "universal" one from the M line. The disassembly/assembly mechanism is, of course, simple, but definitely not convenient. As I said, I'm not sure that changing filters will become something routine for the Xenon 6 owner. Oh, not sure...

A total of three pairs are available: black (-14 dB sound insulation), silver (-15 dB) and gold (-16 dB). In addition to purely affecting the insulation, they also affect the sound. I will talk about this in the next chapter.


No, they are closed, of course, we are not talking about an acoustic performance. The Open Acoustics system consists of three components: open driver, sound reactor and sound reflector. "I have already seen it somewhere!" Yes, it was in the M-line, but it will not be superfluous to remind.

The essence of the solution is that the armature emitters are open. It is clear. Usually, the armature is "packaged" in a closed case, in which the membrane moves, and sound goes output through the channels of the soundtube. It leads to the expected distortions and needs for damping and filtering. Instead, the open driver offers a radiator that does not have a labyrinth of a sound guide, as well as a top case cover. That is, the membrane freely moves air to the outside, into the headphone body, and not into the driver's narrow sound guide.


So we came to the next component - sound reactor. In the previous paragraph, I said that armature radiators do not have the usual soundtubes. Accordingly, all other drivers also do not have a special camera and proper filters and dampers. All drivers are located entirely in the headphone body, that is, the design is completely tubeless. This is a good solution that has already proven itself in both Fir Audio and 64Audio models. All emitters "blow" into the sound reactor, i.e. the headphone body, where the waves are "combined" and output through the soundtube. The filter also performs a purely practical function - protection from dirt and damage.

And here we logically approach the third component of the Open Acoustics system - the sound reflector. The soundtube here does not just provide the final signal, no, inside the tube there is an armature emitter for high frequencies and an electrostatic driver for far HF. The final chord, which you hear, is already forming in the sound conductor. That is, Open Acoustics provides maximum openness, naturalness of sound and the absence of a crossover, sound pipes, filters and damper.


Xenon 6 implements - literally - "rigid" technology. No, it's not about the character of the sound or about nails-like fitting. This is about reliability and durability. Headphones allow the owner, in case of wear of some parts, to replace them on his own, of course, by ordering spare parts from the manufacturer.

After unscrewing the miniature screw, you can remove the 2-pin connector and replace it with a new one. And it is also possible, by squeezing the clip of the mesh filter, to pull it out of the sound pipe (oh, sorry, from the sound reflector!) for replacement.

In addition, for "entusiasts" there are two options for increasing the durability of headphones. First, these are proprietary RCX connectors - the mmcx principle, only the rectangular profile of the connecting elements. Second, the cases are 20% thicker than the market average. Both options apply only to custom versions. They are also covered by a warranty extended to 3 years.


I have already told you about the delusion I was leading myself into, thinking that the Fir Audio Xenon 6 will be descendants of the M4/5 in the sound sense. In this model, an ABSOLUTELY different vision of what a top in-ear monitor should sound like was realized.

If you were lucky (no sarcasm or irony here - I still consider Fir Audio M5 one of the best products on the market) to listen to the previous top from Ukrainian-Americans, you should remember its slightly dry and extremely expressive sound. Well, here it is not like that at all.


Xenon 6 is an example of a fluffy, soft, “big” sound, comfortable and at the same time very informative, where it is difficult to fault the details in principle, but instead, the details are not the goal, and the presentation itself is integral, dense, “thick” and hypertactile .

There is no hint of any heredity or kinship. If you do not know that you are listening to Fir Audio, then you will be sure that it is a product of a different brand altogether. And the novelty is the closest to the "American" sound, while Fir Audio M5 is something from the planes of "Japanese" sound. I don't like any templates or shortcuts, but they are not as appropriate here as ever.

Xenon 6 is warm, and here this warmth is present and felt not as a background feature, as a fraction, but fully, as an archetype. The headphones don't even try to play analytical or transparent. They sound integral, providing a fusion or cohesion of sound. Here it is worth talking not about separation as such, but about MACRO separation. If the majority of tops, and what is the majority - almost the entire top segment gravitates towards emphasized micro-dynamics and separation precisely in the micro layer, then Xenon 6 behaves, let's say, deviant. They do not try to be "like everyone else", but bend their line and sound without accents in the micro dimension.

Xenon 6 gives excellent separation, but in macro. Separating images, being excellent scene geometry and providing excellent localization. Everything else, all the microdynamic potential is here, everything is here, but it is relegated to the background and the listener's attention is hardened to the perception of images as such, in their macro hypostasis. The approach, I will not argue, is not indisputable, but, at the very least, it is interesting, unexpected and worthy of attention. I don't consider myself a fan of this sound, but I can't help but admit a certain charm, persistent allure and sometimes even impudence of this sound. When you expect elegance, airiness and lightness, when you expect curvoisier, but you have the power, pressure, density and taste of 12-year-old whiskey in your mouth.

Recently had a UM Mext for review, and there was a very similar tuning. But this difference in class is evident, with the Mext you get interesting bass and rich timbres, but with some lack of micro-dynamics on highs. Instead, Xenon 6 balance surprisingly finely – they deliver the same powerful, roomy – bone-tactile bass without losing the dynamic highs. Midrange and treble do not feel like an appendage, accompaniment or background, they are, of course, softened, pushed back, but still energetic, embossed and dense. Density is a trump card, it's a joker of Xenon 6. And it's not only about how timbres are presented. And in the sound, as such.

Innuendo - Remastered 2011·Queen

I chose Innuendo as an example, firstly, because of the Queen-like complex and instrument-laden arrangement (well, count how many instruments are there in the composition?) - they are all perfectly positioned and have excellent localization. Secondly, because of Freddie's vocals, which sound like they are in some kind of infinite space. Fir Audio Xenon 6 amplifies this effect and conveys it very skillfully. A magical composition with the right "iron" is the same case.

Here I will say right away: yes, filters affect the scene. Not radically, but they make an impact. Therefore, I will speak primarily from the point of view of the black filter, that is, ATOM XS with the least isolation.

Xenon 6 sounds wide, open, but not too airy. The headphones give a really wide panorama, like the best models of headphones regardless of the form factor. Draw the scene in depth is also great. But here it is worth noting that Xenon 6 are not contrasting monsters, they act differently. Without emphasizing the layers and echelons, their demarcation, or rather, its expressiveness. Xenon 6 work differently - they create a REALLY spacious imaginary stage, absolutely in all dimensions, where they project large holographic images, three-dimensional, full-bodied and - what to avoid - hypertrophied.


Therefore, we are not talking about airiness, lightness and speed here. Xe6's deliver plenty of volume, but it's densely packed with images that the headphones reproduce with frenetic but neat movements. This "amplitude" is clearly measured and agreed upon. No element on the soundbar will feel disproportionately large or small, the Xenon 6 are murderously organic and deft.

The scene has an excellent vertical projection, the images are reproduced convincingly in their authenticity. Both in terms of mass and dimensions. Xenon 6 has excellent stereometric presentation.

Changing the filters from black to silver and gold makes the imaginary scene a little more intimate, slightly compressing the space. As a result, the sound becomes denser, primarily due to the reduction of already conventional "gaps" between sound images. The impact can be assessed as weak, more noticeable interference occurs in the bass area.


This is where Xenon 6 turns on the charisma and zealously demonstrates what the money is asked for. Conventionally, the tuning of the headphones can be characterized as L-shaped, similar to the recently reviewed UM Mext, but it is made in Xenon 6 much more elegantly. As a result, we have accentuated low frequencies with the rest of the spectrum remaining interesting. But in general, yes, Fir Audio Xenon 6 is about bass. If you jump to the conclusion here that they are similar to the EE Odin, then you are kicking yourself as I did with the M5 similarity.

Xenon 6 have warm, accented woofers, the "core" of which is located in the area of the lower woofer layers. The audible part of the sub-bass captures the space, fills all its crevices. There is added weight, impact, and, most importantly, preserved clarity and structure. The bass doesn't just pile on from above again and again, in the case of Xenon 6 we have excellent speed and processing of textures. Layered, weighty, fast, textured bass with well-defined shapes and texture. Dryness is not about him, its blow is not a whip-lightning, but a powerful, piercing punch, when you feel the kinetics of bones, joints and muscles.

The extension is not excessive. The "decay" of the sound is perfectly controlled. The layering is moderate and in general the headphones gravitate towards a fast transient characteristic.

The mid-bass has a more restrained character, it is organic in its coherence with the lower bass, but tuned in such a way as to give a sense of the physics of the sound of instruments of this range and to "feed" the area of lower mid-range frequencies.

Mid-bass Fir Audio Xenon 6 is not emphatically detailed, "sharp". Here, the "open" side of the technologies used in headphones is indicated. There is a similar feature when listening to open full-size models - the middle bass becomes smoother, longer and better "synchronised" with the part of the spectrum that is higher. If you call Xenon 6 bass-head, then it is worth noting that the main emphasis is on the sub-bass component.


Regarding the technicality of the bass. Xenon 6 is not the best model for critical listening to details. They in no way steal them, do not muddy the sound and do not erase lines and boundaries. But they don't do what models in the upper segment usually do. This is a kind of relaxed technicality, when there is nothing to fight about, but the presentation is still built from the point of view of comfort, volume and images - their weight and dimensions. Therefore, it is important to choose a source that provides technical, structured bass with maximum control and dynamics. No softness, no emphasis on overtones in this area and, as a result, a slowed down transients. Roughly speaking, Xenon 6 will be thanked for balanced and high-quality bass with delicious, I would even say, aesthetic bass. This is an audiophile-aesthete bass, not an audiophile-technocrat. I'm somewhere between these two definitions, so I found the Xenon woofers interesting, beautiful, and want to compare them to the M5 and Odin. But more on that later.

Another issue is nozzles. The headphones are heavy, but compact, and, for example, in my case, I needed a pair of ear pads that would provide three things. First, complete isolation and, as a result, full-body lows. Secondly, it would give a sufficient diameter of the output hole without disturbing the tonal balance. And, thirdly, it ensured reliable, tight contact of the heavy and compact headphone with the ear shell. This is necessary in order to take advantage of the Kinetic Bass driver. The work of bone conduction of the dynamic emitter is not as noticeable here as in the Mext already mentioned here. But with the right fit, Fir Audio Xenon 6 gives the same feeling of sound, when it is not just heard through the air, but also perceived by the body.

I will repeat again - any headphones will never replace a pair of good floor speakers, but the experience here is very interesting. If Mext worked in this regard in a wider spectrum, adding flavor to overtones, then Xenon 6 have a clearly lower return and enhance the perception of the main tone. A different method of reproduction does not increase the bass quantitatively, but affects their perception.

Gold and silver filters can add quantitative bass. Moreover, the macro dynamics are enhanced, the sound becomes more energetic. I was not satisfied with both options due to the excess of lower bass and the corresponding suppression of mid/high frequencies. I'm not trying to impose my own impression, but try different filters and draw your own conclusions.

Diana·Paolo Nutini

The bass part is reproduced incredibly realistically and with a tangible transmission of sound tactility. I think it's because of the Kinetic Bass, at least that would be logical. In the first seconds, the bass is almost the leading part, and when Paolo Nutini himself fully enters into the matter, the bass seems to recede into the background, but is still present a little stronger. With tenor voices Fir Audio Xenon 6 does not do the same magic as with bass or baritone. But this effect before the chorus... The headphones almost send you into an emotional knockout. Listen to this track on them.


Japanese funk 1975 released. This is probably the most extraordinary thing in my audio illustrations for all the texts. Xenon 6 bass is not just powerful. At the same time, he remains skillful, dexterous and versatile. And what if funk can test the bass for these virtues? And there are zero complaints about the woofer.


Xe6's midrange is warm, smooth. The lower mids are well fed by the woofers - their mass and density are transmitted to them to a greater extent, and pressure and dynamics to a lesser extent. The tonality is natural, the timbres are saturated, the relative slowness of the midrange contributes well to the saturation of the range with overtones. In general, the midrange can be called natural, warm, integral and with an emphasis on vocals. Especially with a black filter. In particular, "low" - bass, baritone, contralto.

Middle frequencies have a pleasant fullness, the sound is saturated. The same macro-separation manifests itself here. Images in the mid-range are not contrasted and sharp, the sound is smoother and more relaxed. Xenon 6 tightly weaves a rope of sounds from threads, and each thread remains a thread, but we still have a strong rope at the output.

Midranges have a good extension, not as in the case of more "airy" midranges, but the unhurried sound together with a certain viscosity ensure the naturalness of the timbre and the perception of overtones as a physical phenomenon.

Upper mids are a bit restrained. This smoothness suppresses the emotionality somewhat, instead the drive and passion are reflected in the lower part of the spectrum. But Xenon 6 cannot be called extremely emotionally compressed. Because there is a black filter and vocals.

The black filter, unlike the rest, slightly changes the positioning of the vocal, pushing it to the front edge of the stage. Under the conditions of soft, even sometimes viscous mid-range, phlegmatic and relaxed, the forward vocal contrasts perfectly against the background of the bass. This is where the mid-bass character comes in handy. The vocals are excellent - rich, tactile, emotional, especially male. The timbres are reproduced in a magical way. If the bass is here for connoisseurs and aesthetes, who are ready to give their last money for delicious woofers, then with me Xenon 6 such a trick can commit due to work with vocals. Excellent positioning, emotionality and work with trinkets. The technicality of the Xenon 6 lies in the field of midrange and is focused on how the headphones reveal the work of the vocalist.

The upper middle is comfortable, somewhat relaxed, in general, in the general tone of the midrange. Does not force microdynamics and does not add expressiveness. Presence is achieved by the overall performance of the bass section of the acoustic headphone model. Personally, I would like more "pepper" in this area. At the same time, Fir Audio Xenon 6 provides comfortable listening and generosity to poorly mixed phonograms. However, I would not recommend this model for lovers of bright, expressive sound with a neutral to cool character. It will be too hot and stifling for you, my dears.

The Dead of Night·Depeche Mode

The densely recorded lead synth is presented as integrally as possible with the vocal "layer". Moreover, this is precisely the feature of the recording, regardless of the headphones. Xenon 6 with their vocal reproduction perfectly emphasize Dave Gahan's part, primarily due to the naturalness of the voice, separation into "live" performance and synth.

My Name·72 Blues

"Raw", driving and aggressive blues-rock, where almost everything depends on how your system or headphones are able to convey these features. Xenon 6 imposes its character here. A little softness and relaxation suppress the degree of composition. As a result, the crazy drive is not so crazy anymore, and rare-frying is replaced by well-done. And here we are not talking about dryness, no. About the fact that the headphones, by their nature, slightly powder the midrange, preventing them from sounding "dirty and raw" (in the best sense of these words).


Xenon 6 adheres to the same "comfortable" concept of high-frequency sound. They are loose, but not at the expense of spiky and grainy, but at the expense of a good volume created by the headphones as a whole. Xenon 6 has the sound you get with a classic triphonic: the subwoofer gives depth and volume, and the tweeters do the same thing they did without the subwoofer. But due to the depth added by the subwoofer, we get more voluminous and holographic highs.

It is worth noting that the very nature of the sound, the signature itself is not sharp, the energy is not forced, and there is no noticeable focus on microdynamics. The high frequencies are moderately smooth, soft, but still correspond to the flagship level. Adjusted for general tuning, of course. The range is comprehensive in terms of the information it carries. An appropriate level of resolution is provided. It will appeal to those who do not like cold, sharp or aggressive sound on the high frequency as such. Personally I did not have enough aggression and drive on the highs. Xenon 6 tweeters are dense and do not contrast with the overall presentation, but the pressure here is noticeably lower than in the lower half of the spectrum.

The transient characteristic is also not forced here: there is nothing to reproach the attacks for, they are natural, not electrostatically lightning fast (here thanks to the excellent tuning of the EST driver), but they are not smeared either. The extension is also close to natural, but not the maximum. The headphones are clearly less focused on glitter and air than the previous top from Fir Audio. Xenon 6, in particular on the high frequency, sounds more tactile, warm and, so to speak, thick. If you like bright, defined highs, with a pepper on the verge of foul, then this is more about the M5. The Fir Audio Xenon 6 is certainly a masterfully crafted headphone, but from the point of view of a different perception of sound, compared to the one usually associated with TOTL models. But there should be a top for those looking for natural and soft, comfortable and warm sound.

Daddy's Home·St. Vincent

If there is a competitor to Beck in terms of versatility and range of possible sounds both from album to album and within one release, it is probably St.Vincent. Ann Clark supported this reputation with the extreme release of 2021. An interesting composition where each part should be analyzed separately, but now we are "listening" to the percussion. Het here is mostly "closed", clear, articulated. It sounds aggressive and almost brash. Fir Audio Xenon 6 perfectly conveyы the "technical" side: attack, attenuation, timbre. At the same time, it is done in the smooth manner inherent in headphones. However, itis not reflected in excessive length. Only on the character itself.


I personally consider Fir Audio M5 to be the most underrated top-model of the previous generation of flagship in-ear headphones. But M5 has a completely different paradigm based on sound tuning. M5 has a significant less massive bass, it is more even, without such a clear emphasis on part of the range. At the same time, transparency and relief are unsurpassed.

Mid-range frequencies are defined, energetic, the vocals are aggressive in some places, and the overall presentation of the range is sharper and not delicate. Xenon 6 sounds significantly more relaxed here, while it has an advantage in the presentation of vocals. Although it is not as energetic as in M5, it is more natural and, I would say, charming.

HF, as well as bass, is what most contrasts these models with each other. M5 tweeters try to capture and fill as much space as possible, created by headphones, and Xenon's treble resembles a fed cat. Takes up, of course, a third of the bed, but does not claim all of it, and the perfect fur shimmers and shines with every fur. M5 also better emphasizes the distant HF, the work of the electrostatic driver is very noticeable here. They are faster and at the same time longer.


Odin by Empire Ears also has powerful and massive bass. But the nature of that mass and force is a little different. Odin turns all the mass into steel muscles, the bass itself is drier, more structured, has more pronounced separation and detailing in general. Odin woofers, simply put, are more aggressive and driving, punchier and drier.

The middle - here the situation is about the same as with M5, with the difference that Odin's midrange is one of the best in principle that I have heard, regardless of the form factor. A completely different sound compared to Xenon. It's like comparing apples to persimmons.

Odin on highs turn on the turbo mode of detail and expressiveness. Each detail is emphasized, then the emphasis itself is highlighted in a different color and brought to the forefront of your attention. It's also the opposite of Xenon's pitch as much as possible. On the other hand, I cannot but admit that it is difficult to call Odin's highs comfortable at a distance. Here, you either have to really like such a sound, or have a suitable source. Xenon behaves in this range much more obediently and measuredly, but the wow effect suffers a little. In my opinion, the main enemy of Fir Audio Xenon 6 on the market is not only and not so much other TOTL models, but the lack of a wow effect from them against the background of brighter representatives of the segment and, perhaps, inflated expectations after M5. Especially taking into account the differences in tuning.


In principle, the last two sentences from the previous chapter could be a better conclusion. Indeed, it is difficult to blame Xenons, they are technologically flawless, have their own character and correspond to a high level. But in the segment, although not numerous, there is fierce competition, and the price of the model is a little, in my opinion, difficult to relate to the character that the developers have given to Fir Audio Xenon 6.

However, each product has its own buyer. And when it comes to such a subjective thing as audio, even more so. Undoubtedly, I would not be able to recommend the model for purchase blindly (deafly?), here you have to listen, listen and listen again.
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Super bra!


500+ Head-Fier
The Goldilocks of IEMS
Pros: -Excellent build quality
-Ideal form factor--pocketable size, durable metal chassis, attractive looking faceplates (with unlimited custom options!)
-Outstanding customer service
-Unique bass implementation via patented "kinetic bass" technology
-Modular tuning via patented "atom module" technology
-Sound good out of the box--no futzing needed
-Not the Legend Evo
Cons: -Stock cable could be better
-Not the Legend Evo
Disclaimer: All opinions expressed here are my own; I did not receive any sort of incentive, financial or otherwise, to write this review. I am certifiably, 100%, most definitely a human being and not at all possibly a replicant constructed by the Tyrell corporation.
I mean, probably.

Introduction (the tl;dr version of this review):
First things first: I'd like to offer a most sincere and heartfelt thanks both to @Rockwell75 for organizing the North American tour of this IEM, as well as to the notorious @bogdan belonozhko for pioneering what is, in all effects, a nigh-perfect earphone.

Since receiving my tour kit last week, which included the M4, KR5, and XE6 universal fit IEMs from Fir Audio, I've struggled with how best to distill my thoughts into a singular review. And after having thought it over long and hard and late into the night, my conclusion is this: the XE6 sounds good, and you should buy it.

There. That's it. That's my review.

...what? I'm sorry, you wanted more? Look, I get it--you're waiting for some caveat, some disclaimer, some dishonorable mention that disqualifies these, that lets you get up, and point, and shout "see?! I knew these weren't worth $4000! What a ripoff!" And sure. Somewhere out there, that review probably exists. But this review? It isn't it. There's no disclaimer here, no caveat, no hidden trick where I say "these are good except...". No. These are good, and you should buy them. Period.

But (ah--you got me, there it is), if you're looking for a lengthy justification as to why these are good and you should buy them, sit back, buckle up, and let's take a deep dive together down the rabbit hole that is the Fir Xenon 6.

Packaging and presentation

Unfortunately, as my units were received as part of a touring kit, I did not receive the full retail packaging, including the box presentation, of the XE6. Ample photos of the box in question can be found in other reviews, particularly this one on ear-fidelity (no, I'm not affiliated with them--I found them via Google search):

Having seen photos of the box in question, as well as having watched unboxing videos on YouTube, my take on the packaging is that it's...fine? Sure, ok, it's not some luxury, super-dee-duper, ultra high end lux packaging, covered in rhinestones and glitter embossed text or whatever. It's certainly not the felt lined metallic jewelry box of the Sony IER-Z1R. But hey--it's compact, it's clean, and it works.
Look, I get how some people may feel on this: this is a premium item at a premium price and the packaging should feel, well, premium. But man--I live in New York. My Nikes? Premium. My Ray Bans? Premium. You know what else is at a premium in New York? Space, boiiiii. At the cost of these IEMs, I have the privilege of being able to rent a shoebox in Brooklyn for about a month. I don't need some ridiculously oversized box taking up valuable real estate; what I need is something that's compact, clearly labeled, and easy to store, because the reality is, I'm only holding onto this box for two reasons: one, resale value and, two, to store and keep track of my IEM accessories. Outside of that? If packaging these IEMs in a more basic box allows Fir to save shipping and boxing costs? Money which can then, theoretically, go towards saving me, the customer, purchasing costs? Well, then, hey, I'm all for it.

Past the outer box, you've got your basic presentation, which includes some nicely molded black foam inserts (industry standard) that house the stock Fir 2-pin cable connected to the IEMs themselves, below which is a custom leather pouch emblazoned with the Fir Audio rabbit ears logo. Manufacturers, if you are reading this, take note: please stop shipping your IEMS connected to the cable. Please stop shipping your IEMs connected to the cable. I'll say it once more for those of you in the back: please stop shipping your IEMs connected to the cable. Other high end brands are just as guilty of this: Astell & Kern's latest Empire Ears collaboration, the Odyssey, also ships with the IEMs pre-connected to their corresponding 2 pin cable. I am not a fan of this. I have no doubt that the foam packaging is form-fitted enough to house the IEMs attached to the cable just fine without them slipping around; if anything, my issue is that the packaging is too well fitted. In order to keep IEMs from breaking off at the pins when shipping attached to their cable, the foam inserts have to be ridiculously tight, and the result is that it makes getting the IEMs out of the package, while attached to the cable, nightmarish and anxiety inducing. I am clumsy: I have clumsy fingers, and when handling a $4000 IEM, I do not want my first experience out of the box to be this sense of dread and worry about breaking them off at the pins. Add to this that most hardcore audiophiles tend to swap out the cables on their IEMs anyway, and it's an extra step for the end-user out of the box to have to remove the cable.

On the cable itself: it's serviceable. The stock cable that I received with the tour kit was a standard 26awg copper wire, coated in black pvc, terminated in a 3.5mm jack. It was lightweight and microphonics were minimal, and in terms of a functional cable I'm not certain I could have asked for more. If anything, perhaps I'd have liked a little more bling, some pop, maybe some gold accents to match the XE6 aesthetic, but this certainly isn't a dealbreaker. If Fir's website is any indicator, when ordering a pair of custom IEMs, or an upgrade cable from them, you do have some more leeway when it comes to more interesting cosmetic options, including a dark brown cable as a cosmetic alternative. You'll note here I'm not making any comments on sonic qualities of these cables, and that's not because I do, or don't, believe in them, but rather because my experience cable rolling is limited. Given that, my primary concerns when using a cable are two things: first and foremost, build quality and versatility (ie, end connections--swappable adapters are always a plus in my book) and, secondarily, aesthetics. A cable doesn't have to look good to be expensive, but on average, many of the expensive cables are good looking (take a gander at any of Eletech's latest flagships for an example of this). This isn't a $2000 cable; it's a stock cable that gets you from point A to point B, and that's fine, but the more discerning listeners may feel an upgrade is warranted. I will give Fir credit where it's due, which is that their cables have these unique 90 degree angles to them where the pins connect to the jack. Combine this with a mildly recessed 2 pin connector on the XE6 and the result is a connection that feels more durable and less prone to breakage than, say, your standard acrylic IEM shell.

Form factor

On that note, let's take a brief aside and appreciate what Fir has done here visually, because I for one think it's rather clever. IEM models can be confusing, especially for newcomers to the audiophile game, and unless you've been keeping track of brands for a while, it's very easy to get lost in the sauce. A brand like Playstation is intuitive: what's the successor to the Playsation? Why, the Playstation 2, of course, followed by the 3, the 4 and the 5. But look at IEMs: why is one Empire Ears model the Legend X and the next one the Legend Evo instead of, say, the Legend X2? It's not at all intuitive. And Fir is stuck with a dilemma here: how do they make their model names unique enough that they show up on, say, an internet search, but not so confusing that it's difficult for someone to know at a glance what their high end model is versus their lowest tier? The answer, of course, is colors. The M4, KR5, and XE6 may be weird sounding model names, so to make things easy, Fir has followed the route of designing them like Olympic medals: the M4 is bronze, the lowest tier, the KR5 silver, the middle tier, and the XE6--yep, you guessed it, gold. I don't know how much kick a more veteran audiophile might get out of the design, but I for one see what they did here, and do appreciate it.

Visually speaking, I find these IEMs attractive and unique looking. These days, it seems like everybody, save for maybe Campfire, opts for the tried and true visual execution of multicolored acrylic, and it's not that there's anything wrong with that so much as that it's become a little, well, boring. I'll admit, it's hard for me when browsing online to get especially excited about another high end IEM that looks exactly like the blue one I just saw except that this time ooh it's red. Enter Fir Audio, with metal shells in a unique shape with glass faceplates and a gorgeous carbon fiber pattern underneath, marked with the XE6 title logo not engraved but embossed in textured metallic gold foil. I'll just go ahead and say it: these things are sexy. More than that, they're practical: the metal shell feels durable, certainly more so than acrylic, and there's a nice degree of heft to it that leaves these IEMs feeling like a quality, well-built item, but not with so much added weight that they become cumbersome. The shape is also excellent, especially for universals: compared to, say, my custom Noble Kaiser 10s, the XE6's add minimal bulk to my ears, and the interiors of the shells fit almost perfectly flush with my head. And that flush fit is important, because it's how Fir implements their unique bass technology they're calling kinetic bass.

I think of kinetic bass as being yet another implementation, albeit a unique one, of the ever more popular bone conduction technology that we've seen in recent IEMs, including the high end Legend Evo, the lower end Raptgo Hook X, and many of the mid-tier Unique Melody IEMs. Fir has an entire technical explanation on their website as to how kinetic bass works, but the shorthand version is that there's a second grill located underneath the ear nozzle that fires sound directly at your ear and, when placed in as close contact as possible to your skull, creates the sort of bone conduction effect that adds that wonderful extra "oomph" to the end of bass lines and resonance to booming sounds like drumbeats. For those looking for a more visual explanation, I'm no fancy sky-entist, but I had the boys in the lab draw up a detailed diagram of how they believe Fir's bass technology to function:


There are distinct advantages and disadvantages to this implementation. Probably the most obvious benefit is that, unlike Empire Ears, which relies on bone conduction via the ear canal, or Raptgo, which relies on bone conduction via shell contact with the skull, Fir's implementation provides impact bass independent of the main ear canal and shell. The theory here, at least, is that for the universals you could use different tips and, provided they didn't radically push the shells further away from your head, not end up impacting the bass effect. The disadvantage, of course, is that it means it's difficult to downplay the bass impact simply by swapping eartips; that's where Fir's atom modules come in:

Although not the quickest and easiest swap out, the atom modules are fairly intuitive: gold adds bass, black makes it neutral, silver lessens bass, and red, according to the manufacturer, makes the earphones open and transparent, which I imagine is a major plus when using the IEMs as stage monitors. Simply take the included miniature allen wrench, unscrew the modules, then screw in the new ones. Simple, right? It's not the kind of thing I would attempt doing on, say, a moving subway car, but at my desk, it was easy enough to maneuver.

In my case, the XE6 came with the gold modules preinstalled, and throughout my time listening to them, I never felt the need to swap them out. And that brings me to my crowning point here: the XE6 are, in most regards, for all intents and purposes, the Goldilocks of IEMs.

C'mon, you know the story: a chubby, gilded-haired little girl named Goldilocks busts into this cabin in the woods where these three bears live. The bears, having just made their porridge, have only just briefly stepped out, and they've left their breakfasts on the table. Goldilocks goes to sit at the table: one chair is too large, the other too small, but the middle chair--ahhhh, just right. The same with the cereal--one bowl's too hot, the other too cold, but the room temperature one--perfect. Finally, she concludes her visit by going to sleep in their beds--one bed's too soft, the other too hard, but bed number three--well, you get the picture. For me, the XE6 are the first ever IEM I've listened to that, out of the box, I haven't felt any particular need to mess with the tuning via equalizer. I listened to these on direct source via my Sony NW-WM1AM2 (see what I meant about those counterintuitive product names?) paired with some Azla Sedna eartips, and everything sounded, well, right. Cymbals in particular have that satisfying "kshhh" at the top, with just the right amount of treble extension. Strings reverberate, trumpets sing, drums have that nice element of "thump" to them (no doubt enhanced by the kinetic bass) but nothing sounds too boomy, too bassy, or, on the alternative side of that spectrum, too airy or too thin.

For the purposes of my demoing session, I went immediately to my two latest, and favorite test tracks: Gbraakon Escape and Escharum, courtesy of Gareth Coker from the Halo Infinite Soundtrack:

Gbraakon Escape is a wonderful demo track because it starts off heavy, with these thudding, beating drums, transitions slightly into a string piece and then, as the music crescendos, culminates in the main riff as a piano solo, remixing notes from Marty O' Donnnell's original Halo 1, 2 and 3 scores. It's a piece with a wide set of frequencies and instruments, and on the supposedly bassiest gold atom module, the XE6 handles the track with ease. There's a nice impact to the opening drums, but they're never so in your face that they sound artificial. The piano notes have a nice element of twinkle to them, no doubt in part due to the electrostatic drivers at play, and as various instruments go in and out of the track, they sound clean, distinct. I wouldn't necessarily go so far as to call the imaging holographic--I never got the sense of being physically transported to the orchestra hall--but every note that comes in stands by itself, and even with multiple instruments going off at once, there never seems to be any sense of overlap or blurring.

The same goes for a track like Escharum. Heavy drum beats alternate with higher frequencies like strings, and there's a fun little bit of artificial reverb added as transition notes between the intro of the piece and the main chorus. When the strings come in and hit the low notes, they have impact, but they sound clean, natural. I bring up in my opening that for better or for worse the XE6 are not the Legend Evo, and here's where that comparison really comes to fruition.
If I had to compare the two units, both of which claim to be "bassy" IEMs and both of which use very different forms of bone conduction bass, it'd be like this: the Legend Evo sounds like a subwoofer speaker in your head; the XE6, by comparison, sounds like a bass player in front of you. That's not to say one is better or worse than the other; simply that they're very different implementations. Put it this way: you're sitting in a movie theater, watching Terminator 2 in THX. Yeah, you want bass! You want something that sounds like a subwoofer! Explosions should feel visceral, gut-rattling, bowel-emptying BOOM! And sure, that's great, for that particular application. But let's say you're watching a stage performance of Gregory Porter, live in concert, and you're sitting in the first three rows. Yeah, you want bass impact--but you don't necessarily want so much that it makes you defecate yourself. And that's the difference.

To put it another way: listening to the Legend Evo vs the XE6 is a little like having the world's #1 sushi chef in a cooking competition against the world's #2 sushi chef who can also make any dish you can think of. The #1 sushi chef will always be the best at making sushi, period, but that's it--he only makes sushi, and unless you're content with eating only sushi for the rest of your life (and maybe you are, who am I to judge?), if you can make your peace with chef #2 being second best, you get the pleasure of variety, and eating something different at every meal. The XE6 doesn't have as massive a bass impact as the Legend Evo, period, but it does so much else so right out of the box that it's almost impossible for me to find fault with it. The Evo is good for one thing, which is bass, and it does that one thing really well, but the XE6 does that and literally everything else, and listening to it, it's immensely easy for me to see why so many have chosen them as a daily driver.


A quick note about the tuning: these are not, by any means, a neutral tuning, and I'm ok with that. Personally speaking (your mileage may vary and all that) I find neutral tuning really boring. Imagine this: you're college-aged, and you just came back from a date. Your parents ask you how it went: what would you tell them?
"Yeah, mom and dad, it was neutral"
Really? Well, was she pretty? "
Yeah, she was pretty neutral"
Well how did you feel about her?

All of which is to say, if you're looking for something with a flat EQ, look elsewhere. I like the sound signature; I think it's unique, it's got character, and it's exciting. If I had to describe the tuning in a word, it would be this: accurate. Again, I keep coming back to the Goldilocks metaphor: bass is bassy, but not too bassy, treble is extended (but not too extended), soundstage is wide but not unnaturally so, etc, etc. If I was to compare them to a widely available off the shelf IEM, in terms of tuning they match very, very similarly with my Raptgo Hook X. I'm not attempting to discredit Fir by comparing the XE6 to a much cheaper IEM; if anything, it's a testament to Raptgo in terms of how much they managed to achieve at such a cheap price point. I would say if you're cautious about the tuning, try and get your hands on a Raptgo Hook X and, if you like them, take your Hook X, gift it to a friend, and then immediately go ahead and get yourself the XE6. Fir has managed to take a sound signature that I really loved from a relatively cheap IEM and transmute it into a flagship IEM with superior build quality, resolution, and fit, and for that they get very high praise for me.

Closing remarks and a note about customer service
They get even higher praise from me for their customer service, and moreover their availability. As I was eyeing the Fir units for potential purchase, having seen how many audiophiles decided to go the custom route, on a whim I placed a call to Fir Audio to ask questions about their customs process and got put in touch with none other than @bogdan belonozhko himself. Yes--this man actually exists, and unlike Jeff Bezos (or much of the Amazon support staff these days), he actually picks up the phone! Having spoken to him, I could sense his passion for his products, and for sound quality, and although he didn't have long on the phone (he was running to another meeting), he gave me his personal company email and asked that I continue the conversation there, while he looped in another associate of his, Jessica, to assist me. Then I wrote them and something even crazier happened: they actually wrote back! They answered questions! They were helpful, even--dare I say it? Friendly!

I know, I know, this may not seem like a big deal, but let's not forget--the XE6 is a $4000 IEM. Compare this to a company like, say, Astell & Kern. You've got a tech issue? Fill out a ticket on their website. Send an email. Keep following up on said email. Hope that someone emails you back because they're almost impossible to get a hold of on the phone. Ship out your several thousand dollar IEMs. Keep waiting. Keep following up over email and then, eventually, you get your stuff back and, hey, hopefully it's fixed. When that's my experience dealing with customer support (and it very much was when my AK240 Blue Note had to have the battery replaced), it makes me never want to shop from them again. So compare that experience with Fir, and I can tell you that from my interaction with them alone, I want to support Fir Audio as a business. Any place where I can put names to faces, especially with a product this expensive, gets an extra win in my book. Combine that with the numerous positive interactions fellow Head-Fiers have posted about Fir when needing their IEMs serviced, alongside an IEM which out of the box sounds this good, and you've got a winning formula. 5 stars and then some--if you've got the funds, and an itch that can only be scratched by a bassy proper all-rounder IEM, the XE6 is calling your name.
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I’m either going to get this or the fir kr5 next. Not sure which yet! Great review though
Great review. Your Lab sketch is hilarious!
Why are the connectors reversed on the IEMs in the 3rd picture ("Form Factor")? I hope you didn't review them like that! :relaxed:


100+ Head-Fier
Fir Audio Xenon 6 (Universal)
Pros: Best low end ever
Work of art
Atom module versatility
Cons: XS atom modules are somewhat cumbersome to change
Tuning takes some getting used to

After spending about a month with these, I can confidently say they're the best IEM's I've ever heard. 5/5 since they fall firmly in the category of headphones that make me want to listen way too loud, even though I know better. Seriously, they're addictive.

Overall, I'd describe the tuning as mostly neutral with base boost with a very full presentation. Definitely wouldn't call these laid back, but everything is delivered smoothly and effortlessly.

These are bassy headphones, like comparable that of the TH900, but with even more sub bass extension. If anything, these deserve TOTL status for just how technically impressive they are with the quality and quantity of low end they have, yet still remaining incredibly precise and detailed.

Honestly, the very first time I listened to them it was frankly a bit overwhelming, but after swapping around tips and atom modules, I got a sound that worked for me.

For listening, I used an iFi Gryphon and Symbio MandarinEs tips. Most of the time, I had the silver atom modules installed.

IEM Comparisons

I was able to A/B the Xe6 pretty closely with the 64 Audio Tia Fourte by using IE match on the 4.4mm output with the Gryphon, and plugging the other IEM into the 3.5mm jack, which volume matched them pretty closely. My only other IEMs at the time were Yume Midnight's which, I mean isn't really a fair comparison.

Both being flagships, they are definitely excellent in their own right, and while I can't say the Xe6 won in every category, 90% of the time I went for those over the Fourte.

The main difference between the two is, of course, the Xe6 having vastly superior low end. In contrast, the Fourte has more of that sparkly treble that made them my previous favorite IEM. The Fourte also has slightly wider soundstage, and is more airy and laid back, while the Xe6 is more musical and full, especially in everywhere outside of the highs. Also, even compared to the Fourte, the Xe6 made me realize parts of the music I'd never noticed before.

Full Sized Comparisons

Of my collection, I think the sound signature is closes to that of Argons, but refined to an extremely high level. Like where the Argon's may get muddled or lose some of the mid range or detail, the Xe6's perform perfectly. Not to mention the Argon's don't really have comparable sub base.

Compared to the Verite Closed, the Xe6 is a bit more v shaped, and a lot bassier. Maybe like 10% more treble and 25% more low end. VC are also wider and are again more airy/sparkly where the Xe6 are full and warm. Technicalities and detail are roughly on par with one another to my ears.


I'd recommend just on the grounds of the kinetic bass. Audiophiles are spoiled for choice, but every once in awhile something comes along that is truly unique. These are just that, a truly one of a kind experience. However, if you're really into a neutral or laid back sound signature, these might not be the best choice. In my opinion, these perform best with bassy music (EDM for me), but also music with a heavy string focus, like just someone singing with their acoustic guitar all the way to big, orchestral music.
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Great impressions~!
How about the sound leakage since it has open kinetic bass hole? I wonder if that affects any sound going out and coming in.
I think it's pretty negligible. Maybe the person sitting next to you in the library might notice, but I think under most condition's it wouldn't be an issue.
^literally this. I'd imagine your spouse sleeping next to you might mildly hear them, but yeah, no one at work is going to give you the stink eye if you wear these at your desk.


Reviewer at Ear Fidelity
Fir Audio XE6 Custom
Pros: A piece of art
Perfect build quality
Comfort for days
ATOM modules basically give you 4 different IEMs
Great accessories and cable
Godlike tone
TOTL detail and resolution
Huge and accurate soundstage
The bass is just something else
Arguably world's best dynamics and slam
Great with every music genre
Sounds great even from a MacBook
Cons: It is very expensive. Worth it, but still expensive
I don't luxurious packaging?



Fir Audio is still a rather new company compared to the ancient ones like Noble or 64 Audio, but they certainly need no introduction. With their vastly popular M series, as well as their highly praised VxV model they made a name for themselves as one of the top players in the high-end IEM market.
Actually, here at Ear Fidelity, we’ve already reviewed their VxV model (review here, video review here) as well as their previous flagship custom IEM, the M5 (review here). Heck, the M5 actually won our “Best Custom IEM of 2021” award. This has been one of the most used earphones for me in 2021. Actually, when I was going to the Caribbean for my vacation, I only decided to take 1 pair of IEMs, and I picked the M5, which should tell you more about my feelings towards this model.
For me, Fir Audio is the company to grow even more in the upcoming years. They’re out there doing stuff they like, in a non-compromise way while also trying new and exciting technologies, like their Open Acoustics System, Atom Venting, and now the brand new Kinetic Bass.
You see, high-end audio isn’t just about making good products. It’s also about pushing the limits, taking risks, and most importantly…having faith in your product. You’re developing a product with a price tag of 4000 USD, you can’t succeed if you don’t actually believe that your product is worth that much.
So, we already know that Fir Audio is capable of making great-sounding IEMs with some class-leading build quality and design, let’s dig in and see how their new flagship XE6 looks and sounds.



Just like the M5, from the first moment you get the packaging of the XE6, you’ll know that you’re experiencing something nice. I really like the new graphics for the box and the yellow colorway. While this packaging is definitely not “luxurious” or really high-end with wood, gold, and all that, it is a good side of modesty. Rock-solid, cool-looking, and simply proper.
Inside the box, you’ll find the XE6 IEMs of course, an included cable, a really, really, really fantastic stripe (that’s such a nice touch), and a carrying case with ATOM modules and a cleaning tool.
Let’s start with the cable. While designing the CIEMs on the Fir Audio website you’ll have a few options here and there. What’s the most important is that the included cable is worthy of including with a $4000 product. It’s an 8-core copper cable that is both comfortable and reliable. It doesn’t tangle, it looks good and sounds good, there’s nothing more you could have asked for.

Next up, the carrying case. This is hyper-subjective, but I just like the previous one more, mainly due to its beautiful, gorgeous burgundy color. The new one is black and made of genuine leather, but it looks a bit bland in my opinion. It’s a FANTASTIC case, but it’s just not a “looker” for me…well, better not to try to understand me, I’m kinda twisted about colors.
Inside the case, you’ll find three different ATOM modules (the fourth pair is installed on the XE6 directly) and a cleaning tool for taking care of these beautiful babies.
Overall, the unboxing experience and the included accessories are both fantastic and truly worth calling high-end. There’s a certain “pro” approach to it, where function beats luxury, and this is my kind of thing when it comes to audio.

Design and Build​


Important note: I have a custom version, so this entire paragraph doesn’t apply to the universal version that you’re able to buy off the shelf. The design is also highly subjective as well as depending on the actual design you’ll go with.
But boy, oh boy. This is BY FAR the most beautiful thing I’ve seen in the IEM world. Nothing comes close to it. The new “Titanic” design of the faceplates is just ridiculous. I paired it with matte gray shells after Ted from SuperChonk Super Audio Show recommended me this combination….and he was 100% right (thank you, Ted!).
Let me brag about the look a bit more here. No photos in the world can really show the amount of precision and texture that these IEMs have, it looks as refined and as artistic as it gets. This is hand’s down the best designed, executed, and “painted” pair of earphones ever, and I’ve worked in a CIEM company in the past, so I’ve seen things.
Okay, into the actual quality now. The shells are just perfectly smooth and the build quality is perfect, end of story. As I said in the review of the M5, Fir Audio mastered the build quality and they reached the “Game Over” picture at the end of the game called “manufacturing custom IEMs”. The nozzle is a big improvement over the M5 now, as instead of a simple mesh found in the previous flagship, you’re getting something more secure and nicer looking now. Little details that make great perfect. There’s also one more change to the actual shell of the XE6 over the M5, and it’s the new Kinetic Bass cutout. For this wonderful driver to actually work it has to have that vent on the inside of the IEMs, where it touches your outer ear. It is (as you could have expected) just perfectly finished, with no rough surfaces, no imperfections. To see something that little being such perfectly built is really amazing. Fir Audio, I respect that so much that you can’t imagine.

As you would have expected from a high-end custom IEM, the comfort is just ideal. This is a perfectly machined IEM built specifically for my ears, what else could I get than perfection? One thing to note is that matte customs behave a bit different than your standard “glossy” acrylic, so keep that in mind as they need a little time to get used to. After that “burn-in” time has passed, you’ll be handling customs that are just so comfortable that it’s just like a definition of this world. Remember the story about going to the Caribbeans? Well, I spent 10 hours on a plane with the M5 in my ears without a single break – no problems whatsoever, they are that comfortable.
Lastly, when ordering the custom XE6 you can choose between 2-pin and RCX connectors. I’ve heard great things about the latter, but as a reviewer, I just couldn’t do it…I cable roll a lot, and I have literally zero RCX cables. What’s changed over the previous generation is that you cannot order MMCX anymore, and that makes me sad a bit. My custom M5 has MMCX connectors, I really like them and this is my favorite connector in the IEM world. It is what it is tough. Probably MMCX takes too much space in the shell, that’s my wild guess.



Let’s start this paragraph by covering the drivers configuration. The XE6 sports a single, hybrid Dynamic Driver for low frequencies, one OpenDriver Balanced Armature for low frequencies, two for midrange, one for high frequencies (this one uses a Sound Reflector), and a single OpenDriver EST driver for ultra-high frequencies. The times when people used to think “more is better” are long gone, so I’m not going to brag about the driver count. What’s important though, is the mind behind a certain configuration, as well as implementing some interesting technologies that actually make sense.
So, let’s discuss that Dynamic Driver, shall we? Some time ago, there’s been dynamic driver IEMs, everyone was happy and the market was pretty much as boring as it gets. Then, Balanced Armatures came and conquered, rapidly taking over a vast part of the IEM market. People started to use 2,3,4….18 of those and basically cut the frequency response into million little pieces, which was not really ideal. After a while, people started to notice that Balanced Armature drivers can’t really give us that big, saturated, and physical bass response. This was the turning point when so-called “Hybrids” started to show up. A Dynamic Driver for the bass, Balanced Armatures for the rest, that makes sense. I myself don’t really want to use anything different than DD for my bass. Vision Ears Elysium – brilliant IEM, poor bass response. What driver does it use for the bass? One Balanced Armature. End of story.
But! It doesn’t end there. There’s a company called Unique Melody, pretty much a “Mad Scientist” of the IEM market. They took a bone conduction headphone (oh gosh these are terrible), and wondered – damnit, it kinda makes sense, maybe we can get something out of it to use in our IEMs? So they experimented, once again, like a Mad Scientist, a Genius working overnights in his secret laboratory, and they came up with the model called MEST…and MEST changed everything.
But hey, this is a Fir Audio review, why do you tell us about Unique Melody? You see, they revolutionized dynamic driver technology in IEMs, and here we are, Fir Audio making another step.
The low frequencies Dynamic Driver used in the XE6 is basically a hybrid that does both air conduction as well as bone conduction. It is faced towards the cutout on the inside of the IEM, as seen in the photo.

This gives you a bass performance that is just incredibly physical and hard-hitting without being too bloomy. You see, when you listen to a nice stereo setup, you’re not only hearing the bass, but you’re feeling it as well. This was the main goal for Fir Audio to achieve, a sound that you can feel. I’m glad that more and more companies are pushing this kind of technology into their offerings, giving us, the customers a more refined, fun, and lifelike audio performance that was basically impossible to achieve just a couple of years ago. This is a brilliant example of how the IEM market grows and improves every year, and it doesn’t look to be stopping anytime soon.
Another cool feature of the new XE6 is their “RIGID” technology. This is basically a compilation of critical parts of the IEM that have been vastly improved to achieve great longevity and durability.
First up, the 2-pin sockets used are the most durable 2-pin connectors on the market, rated for 1000 connections without any issues. It uses a revolutionary quadrant socket design that prevents the socket from getting loose. This has been by far my biggest complaint about 2-pin in the past. I used to have a few 2-pin IEMs that got loose, and it’s never good. Actually, I know of a Noble Khan unit that got so loose, that it is basically unusable unless you’ll glue the cable permanently. Who would want to do that with such an expensive pair of IEMs?
Of course, whether this statement from Fir Audio is actually true, we might need a lot of time and a lot of Frontiers series IEMs in the wild. Good thing is that Fir Audio actually looked into the problem and came up with a solution, and if the solution is valid…we’ll see about that in the future.
The nozzle protection got an upgrade as well. Now sporting a snap screen that makes replacing the mesh much easier as well as giving better protection against debris etc. Also, it just looks more polished and elegant than just a plain mesh. Nice touch.
Lastly, the Rigid 3D Printed Shells. Fir Audio makes their CIEMs 20% thicker than the industry average to increase durability. Thicker shells mean more protection for valuable drivers inside of the IEM. You don’t want to ruin your new $4000 CIEMs because you gave them a little hit. They are both made to look extraordinary as well as being durable and resistant to minor accidents. While you don’t see that one with your own eyes, the moment it saves your CIEMs from breaking it starts to be one of the most important aspects of the new design, doesn’t it?
Last but definitely not least, the Atom modules. Let’s get into a separate paragraph for these.

Atom Modules​


I can’t stress this enough – just get the interchangeable Atom modules. It’s a $149 update, to a $3899 IEM, it’s not even 5%, and it basically makes the XE6 into four different pairs of IEMs. Don’t be ridiculous, it is way more than worth it.
So, the interchangeable ATOM modules are basically small acoustic filters that you can swap out on the go to change the level of sound isolation, hence the sound signature. You’ll get four different signatures depending on the module you’ll choose. This is an absolutely brilliant thing to have, as it really allows you to fine-tune the sound to your preferences or to your current mood. The modules are as follows:
My favorite have been the Gray ones, as they offer the most balanced and neutral sound from the rest of the modules, while still maintaining that beautiful tone of the XE6. However, that’s just me, and you might end up with different modules as your favorites, or actually using all of them regularly. The choice is yours, and having a choice is great.
Next up are the black modules, which are pretty similar to the gray ones, but with a slight emphasis on the bass frequencies. The XE6 itself has a fantastic bass response, so I tend to use the Gray modules more. If I’m listening to something that is really bass-heavy and I want that huge and epic bass performance though, the black module is a great thing to have and use.
The gold filters are the most bassy and they also give you a boost in the upper areas. This makes the XE6 into a more V-shaped IEM if that’s your thing, but things start to sound a little extreme in this configuration. That is probably something that a lot of people will look for with this kind of module, so I’m happy to report that the gold filters might be your ultimate “fun” modules.
Lastly, the red filters are the brightest and leanest sounding. I’m not gonna lie, these are my least favorite, as they somewhat make the XE6 into extremely detailed beasts which lack body and timbre a little. This could be the best module to go with some Asian music, as they hugely depend on the upper-midrange, but it’s not my cup of tea.
What’s the most important in all of this though is that you’re paying a lot of money for a pair of IEMs that you can tweak to your preferences. No module will change the XE6 into a completely different IEM, but this is actually a good thing. This is an exceptionally tuned IEM that you can slightly modify to fit your personal taste. This is a huge win in my book and by far a no-brainer when it comes to paying that $149 extra. I wish more manufacturers would implement a tech like this, so you can have a choice of adjusting the sound of your new IEM ever so slightly.



Okay, the sound quality, the aspect you’ve all been waiting for. I really love the previous flagship of Fir Audio, the M5. It’s been my go-to pair of IEMs whenever I’m traveling, and now it is retired in this aspect because of the XE6. This IEM is such an improvement over the M5 that it actually became my favorite IEM in my collection, even beating my all-time favorite Unique Melody MEST. So yeah, that basically means that the XE6 is now my favorite IEM, and this means a lot for me personally.
The XE6 sounds incredibly engaging and euphonic, to the point where it is actually pretty hard for me to review it in a proper way. This sound gives me so much emotional rollercoaster that it’s hard to focus on the sound alone, as I’m flying through space and time with my eyes closed, experiencing one of the most fascinating audio journeys in my life as a headphone enthusiast and reviewer well…ever.
I just can’t stress how important this kind of experience is in high-end audio. You’re not paying $4000 for just detail and resolution, it HAS to be so much more than that to even come close to being a reasonable buy. However, if an IEM that costly gives you a kind of emotional feeling that you’re actually starting to listen to music more and discover new and fascinating stuff, then it’s definitely starting to look more well-worthy.
Oh, if you’re our regular reader then you know what all that above means. Pawel gets emotional, so the review is going to be Uber-positive. I tend to get highly “poetic” when I really like the product I’m reviewing, and this time…this might be more than “like”. Let’s jump into it. Oh, almost all of the sound descriptions below are made with the Gray Atom filters on, as they are the most neutral and kind of “stock”.

The bass…how do I put it. You’ve read the TECH paragraph, you know that the low frequencies driver is an absolute breakthrough for both Fir and the entire IEM market, and damnit, it does work like a charm. Unique Melody started this great fashion of going Bone-Conduction with the bass, and this one takes it to the extreme.
I’m listening to a song called “Persephone” by Wishbone Ash literally right now, and I’m just blown away by the physicality of the sound I’m getting. The rhythm section with the bass guitar in the lead has so much depth in this song, I never heard it before, even when I was listening to it on those crazy $100k+ stereo systems. Also, Wishbone Ash is known for its dual lead guitar passages, as a sort of a band trademark. This gives you an extraordinary stereo effect where you’ve got a lead guitar on both sides of your head playing simultaneously, and when we’ll get into the soundstage, then I’ll explain a bit more.
Let’s get a bit crazier. “Motley Crue” by Post Malone (by the way, does anybody know what the deal with that title?). This is a modern track and it’s Post, so you can expect some intensive bass action in this track. Well, the XE6 does sound absolutely ridiculous, I actually get a feeling that the IEMs are vibrating heavily in my ears, this is such an interesting feeling that it’s hard to explain, you would have to hear it.
Okay, okay, the bass has a great body to it and it’s really fun, but how are the technicalities? It reaches very low, down to hell and beyond, its resolution is just incredible, and it’s as fast as it gets. This can be rivaled only by the MEST and the MEXT by Unique Melody, but I actually think that the XE6 outdone them both in terms of the bass response. It’s just that good. I’m glad that more companies are going in a direction of new technology for the low-frequency drivers, it really does pay off. For now, the bass response of the XE6 is the best I’ve heard.

This is an emotional review, and we’re getting into the midrange, so you know what’s going to happen now. Lunatic Soul with its “A Thousand Shards of Heaven”, you guessed it. How does my beloved Mariusz Duda sound on the XE6? This has been my benchmark for vocal reproduction ever since this album has been released in 2017. Okay, straight to the point Pawel…well, it sounds absolutely splendid. Mariusz has one of that heavenly voices that just scream for a full-bodied, lush, and smooth type of sound, and the XE6 simply delivers all that. It sounds naturally warm, romantic, and just beautiful. It doesn’t end there though, as there’s also so much resolution and the detail retrieval are just both top of the line. I don’t know if that’s because of the drivers that Fir Audio is using, or their open acoustics system, or actually both, but this midrange presentation is just the best of both worlds – smooth and tonally marvelous while being extremely technically capable. Because of headphones like the Hifiman Susvara or the XE6 I’m reviewing today, I’m starting to have a weird feeling about the resolution of the sound. Like…how does it get better than this? How can this be improved? Every time I’m listening to both of these headphones I imagine that it’s all there is. I’m sure it’s not true and I’m just being ridiculous, but to even have this kind of feeling means a lot, doesn’t it?
Okay, back to business. Next up, a song called “Organs” by an Icelandic Indie Rock band called Of Monsters And Men. I’ve chosen this song, because it’s poorly mastered, and who listens only to well-mastered albums anyway? How does that crazy resolution and detail retrieval work with that kind of music? Actually, just about perfect. Because of the beautiful, smooth tonality of the XE6 the voice of Nanna sounds fantastic, even though it’s been kinda butchered by their sound engineer. This is the treat of the XE6 that is very impressive – it’s absurdly resolving, but never aggressive or analytical sounding, so you can listen to your favorite music without being in pain.
Lastly, the legendary “When A Blind Man Cries” by Deep Purple. Oh, what a song that is. It’s actually a personal nr3 ever of both me and my father (yes, we have that sort of list, cool isn’t it?). This is just a perfect ballad and the voice of Ian is just hypnotizing on the XE6 with that sweet timbre and thick note delivery. It sounds both intimate and vast, giving you a beautiful yet refined sound performance. Absolutely stunning.
The treble is just as impressive as the rest of the sound. It is a very reference-like sounding with its wonderful resolution and smooth delivery. It never is in the center of the actions, it never takes the main spot, and this is the best thing that could have happened with this IEM. There’s so much going on in the bass department and the midrange is so god likely beautiful, that a forward-sounding treble could have ruined its magic. Instead, this is just a beautifully smooth, coherent, accurate, and detailed sounding treble that is just impressively neutral.
Its character is easy to spot with rock classics, so let’s go and grab one. A song called “Catch The Rainbow” by Rainbow is a hard (prog? classic?) rock giant with one of the best vocalists well…ever in front of the microphone – Ronnie James Dio. The grandpa of heavy metal has ironically one of the most calming and sweetest voices in rocks history, and he was at his top when Ritchie Blackmore offered him a place in Rainbow after leaving Deep Purple. Back to the track though – it’s a 1975 rock album mastered by Martin Birch, who was responsible for Maiden’s albums. It’s not a mastering wonder, so you clearly don’t want a harsh or overly bright-sounding IEM anywhere near that album. The XE6 however does wonders to this album with its smooth and neutral treble response that is never piercing, yet detailed and accurate enough to get a very natural and realistic type of sound reproduction. It just sounds right, but never wonky or dark…this is outstanding.
I have to address one more song though. “Chocolate Chip Trip” by Tool is a type of scenario when Danny Carey walked into the studio, looked at the rest of the band, and said – listen up, I’m just going to sit by my drum kit and play something so epic that you won’t be able to walk for the rest of the day. And he did just that. It’s just him, arguably the best drummer who ever played rock/metal, his drums, and some weird electronic sounds. How does that sound on the XE6? As epic as the song itself. Because of the utterly monstrous dynamics of the XE6, this song kicks your eardrums and takes no prisoners when it comes to fun delivery. Everything, the bass, the midrange, and treble sound just incredibly natural and physical. Wow.
The soundstage is also absolutely amazing. The width is great, the depth is fantastic, and the imaging is basically perfect. Remember when I wrote about Wishbone Ash and their dual leading guitars? If I close my eyes while listening to their “Persephone” I’m being hugged by these two guitars from both sides and they sing me a beautiful lullaby. The XE6 is capable of giving such an extraordinary amount of separation and layering that you’re going to have a hard time believing that you’re listening to an IEM and not a big over-ear planar or electrostat. The XE6 is also capable of producing an ink-black background, which further improves the sensation of the soundstage being absolutely humongous. Finally, an IEM that can match the soundstage performance of the UM MEST. While I won’t call the XE6 specifically better in this department, it is better in everything else, and seeing how much I’ve praised the MEST over the last year certainly means something.


Fir Audio M5

The M5 has been my favorite custom IEM that I ever had…until I got the XE6. The latter is such an upgrade over the previous flagship that it’s actually scary what these guys can do. The XE6 is better in every single regard, mainly in the bass department and the overall technical capabilities.
The M5 is still a great pair of IEMs, but the XE6 is just a clear upgrade, which is great to see. It’s good that the company is going forward and that they actually improve their models, rather than doing something new, but not entirely better. Of course, the retail price of the XE6 is way higher than the M5, it actually costs $1100 more, but trust me, when you hear them both…it’s more than worth the premium.
Unique Melody MEXT


This comparison came to my mind rather naturally, since both XE6 and the MEXT use ground-breaking bass technologies with bone conduction.
The MEXT is a fantastic value for $1100, but it’s not a perfect IEM. The price difference between the MEXT and the XE6 is huge, and it comes as no surprise that the latter is just superior. Both IEMs have extraordinary bass responses, but here the similarities end. With its beautiful yet smooth-sounding midrange, a reference-like treble response that is just incredible, and a soundstage that doesn’t get better than this, the XE6 proves to be a lot better than the MEXT.
For the price of the XE6, you can get more than 3 pairs of MEXT. Is it worth it? I’m not the one to judge this, it all depends on your wallet and how crazy about audio you are. If you want me to answer which IEM is objectively superior, I’m going to say the XE6, without a single hint of hesitation.
Vision Ears Elysium

I reviewed the Elysium quite a while ago, but luckily I got the chance to listen to it again lately. It actually surprises me how much has it aged during that time.
I mean, this comparison is lost for the past VE flagship on the bass section alone. The bass of the XE6 is so much better than the one in Elysium that it actually sounds almost unfair. I don’t even want to go into great details here – everything, from the physicality, to extension, detail, resolution, note weight…the XE6 absolutely demolishes the Elysium brutally.
Other than the bass, the Elysium seems to catch up if you’re into light and ethereal sounding IEMs and you’re into classical music, but that’s about it. The XE6 in comparison is meatier, heavier, and more natural-sounding, with a smoother and more refined overall sound. I know it would have been more logical to compare the XE6 to the latest EXT and PHONIX, but I’m yet to try them, so Elysium it is.
Final A8000

The legendary flagship of Final Audio, the A8000 is still a benchmark for speed and resolution in 2022. Let me tell you that – it’s here to stay a bit longer. It still manages to sound incredibly fast, even compared to a monster like the XE6.
It’s in the tuning though, where the XE6 starts to sound like a more expensive IEM. The A8000 gets a bit shouty and aggressive, where the XE6 is just wonderfully musical and smooth, without sacrificing any technical performance. The XE6 is a slightly more detailed IEM than the A8000, but this difference is not as big as you might think.
Lastly, the A8000 only comes in a universal fit, and it’s a hit or miss with its polished SS shells with sharp edges. On the other hand, the XE6 is available in the custom version, and the build quality and comfort are just…perfect.



I find the XE6 to be very forgiving with the source choice and the music you’re listening to. Actually, it sounds absolutely magnificent right out of the jack output of my MacBook Pro 2021, giving me a truly high-end level of sound.
It paired absolutely beautifully with the Cayin N8ii back when I had it. This was the pairing that was just so natural and pleasing sounding that it was hard not to listen to it.
Other than that, the XE6 sounds amazing out of basically everything. The EarMen Colibri, which I have just reviewed has been a great choice with the XE6 as well. This is just a wonderful IEM that doesn’t need the rest of the system to really shine.



Writing this review has made me realize how lucky I am. Out of many products that make their way here to the Ear Fidelity HQ, once in a while, there’s something that is special, something that changes my way of listening to music for some time. The Fir Audio XE6 has been one of those products, giving me such an emotional ride that I actually started to listen to music more.
With its simply perfect build quality and comfort, outstanding design choices, great accessories all the way to its incredibly engaging and capable sound quality, it now becomes my answer to the question “What’s the best IEM that you’ve ever listened to?”. The Fir Audio XE6, hands down.

Wildly recommended.


Gear used during this review for the sake of comparison and as an accompanying equipment:
  • Headphones – Unique Melody MEST, Final A8000, Fir Audio M5 custom, Effect Audio Axiom, Campfire Audio Solaris 2020, Hifiman Susvara, Meze Elite
  • Sources– Poco X3 Pro, MacBook Pro 2021 M1 Pro, Cayin N3Pro, Cayin RU6, Cayin N8ii, EarMen Colibri, Fiio M17, Fiio M11 Pro ESS, Earmen Tradutto, SMSL SH-9, Musician Aquarius, Ferrum OOR
Big thanks to Project Perfection and Fir Audio for providing the XE6 for this review. I wasn’t paid or asked to say anything good or bad about this product, all of the above is just my personal, unbiased opinion. Fir Audio hasn’t seen this review before publishing it.
For UIEM , I think it too warm.
But I'm not sure with CIEM .
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Would have wished for an comparison to the IER-M9 because its even faster than the A8000 but tuned much warmer. But obviously you can not compare them against every IEM that exists.
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@Vamp898 Yes, that's unfortunately true :beerchug:


100+ Head-Fier
FIR Audio XE6: look beyond sound
Pros: Sound, comfort, design, build quality and materials
Cons: Price
Hi friends!

In these troubled days, when the reality around us has become so fragile and defenseless, we offer, at least for the time of reading this article, to be transported to the world of perfect sound, where you can find peace and joy.

Today we have an appointment with the American company FIR Audio, whose creativity (that's right!) always arouses my admiration. Following the highly popular "M" series and VxV IEM, the brand has introduced its new premium line of in-ear monitors FRONTIER SERIES, which includes three models: NE4 (Neon 4), KR5 (Krypton 5) and XE6 ( Xenon 6). We will take a closer look at the latter.

All the three novelties listed above use the latest proprietary developments, namely: KINETIC BASS, ATOM VENTING, OPEN ACOUSTICS, RIGID TECHNOLOGIES, and TUBELESS DESIGN. I will talk about these know-hows in more detail in the review itself. In general, in my opinion, FIR Audio is one of the most technologically advanced and promising companies in portable sound. These guys never cease to amaze me. They do not throw big words, but work hard, they definitely go to the goal and achieve amazing results, and they do it extraordinary.

Like all FIR brand IEM/CIEMs, Xenon 6 has a hybrid design: here, as you might guess from the name of the model, there are six drivers of three types on board. In addition, there is also a replaceable Atom-X module, as well as a unique design implemented according to the Tubeless Design principle - the patented FIR Audio technology, which implies the rejection of acoustic tubes and the open design of the drivers themselves. As a result, not only the acoustic design of the case, but also the very structure of the internal components of the in-ear monitors, has been worked out with precision.

I already wrote about the M4, M5 and VxV models earlier, now it's the turn of the novelty.

Well, it's time for us to get directly acquainted with the new technological miracle, the flagship in CIEM performance, the amazing Xenon 6!


Text: Alexey Kashirskey (aka Hans Barbarossa)

Type: in-ear
Construction: hybrid
6 drivers per IEM/CIEM:
1x 10mm Kinetic Bass Dynamic Driver
1x OpenDriver Balanced Armature Driver for bass
2x OpenDriver Balanced Armature Driver for mids
1x OpenDriver Balanced Armature Driver for highs (with Sound Reflector)
1x OpenDriver Electrostatic Driver for ultra highs
Technology: Tubeless design, Atom Venting, Kinetic BASS, Open Acoustics, Rigid Technologies etc.
4 interchangeable Atom-X modules included
Freq. Range: 20-20kHz
Impedance: 28ohms
Cable: detachable - 1.2m/1.6m, connectors (2pin), jack-3.5mm

Design and sound without limits: CIEM individuality or UIEM versatility

Before starting the review itself, it should be noted that FIR Audio in-ear monitors can be ordered both in universal (IEM) and custom (CIEM) versions - the choice is up to the buyer.
Well, for those who have not yet encountered CIEM, I can assure you that the procedure for ordering a CIEM version is not difficult at all. You need to go to the site, register, go to the "Designer" menu, select the desired model, its design (appearance, connectors, cable length) and pay for the purchase. Then you go to the hearing center, make your impressions / imprints there and send them to the manufacturer. After that, look forward to the arrival of your exclusive in-ear monitors.

In our case, the XE6 model is made in CIEM version. And now it's time to go directly to the acquaintance with this technological six-driver miracle!

Appearance, kit, technology and ergonomics

For anyone who has ever listened to any FIR Audio in-ear monitors, the company's logo immediately gives the command to goosebumps to start running through the body in anticipation. And now, having cast the first glance at the box in which Xenon 6 are, I saw these perky bunny ears and immediately wanted to quickly unpack everything and immediately start testing. But in our business, there is no hurry, so let's still consider the packaging.



In addition to the logo on the front of the box, we see a graphic image of the XE6, which, like a space satellite, soar among the stars. In the lower right corner, there are three round icons representing the technologies used in the model: KINETIC BASS, ATOM VENTING and OPEN ACOUSTICS. And this is only part of the know-how.

The side of the box have adopted the golden sticker "XE6", the brand logo and the inscription indicating that the headphones belong to the new line "to New Frontiers". Detailed specifications are listed on the back of the package.



We remove the printing wrapper and find a black box, where we again encounter the FIR Audio logo in the form of rabbit ears, applied with gold embossing, from which sparkling sun rays scatter in all directions. And then my goosebumps began to dance the cancan!

We open the box and find what we are looking for: CIEM encrusted in a foam base with a replaceable cable (2pin / 3.5 mm) already installed, a cool leather puck case designed for storing and carrying in-ear monitors (in the CIEM version it also has the name of the happy XE6 owner engraved ), instructions and a round colored FIR Audio Space Force sticker. Yes, with these headphones you fly into space! But this is already a spoiler, back to inspection.



Three pairs (silver, gold and red) of Atom-X plug-in modules fit neatly inside the case, and another pair - black - is already installed in the CIEM. Next, we take out a brush to care for the sound pipes.

In general, the set is five-star, it has everything and a little more.

The CIEM acrylic shell in Matte Black is impeccably executed. This is a first-class performance, where every curve, every turn and bulge perfectly follows the shape of my auricle and ear canal - surgical precision! The design with its impeccability resembles the perfection of Michelangelo's sculptures. The shell itself is small and weighs almost nothing. This is perhaps one of the lightest CIEMs I know of. And the tactile sensations and ergonomics are simply incomparable!




Sound isolation is average, no worse and no better than most in-ear headphones. However, Xenon are not intended for the bustle of a big city, music in this quality should be enjoyed, fenced off from everyday frailty. Well, if you still want to take the headphones with you to the street or to ground public transport, then listening there will be quite comfortable. But for the subway, I suppose this may not be enough.

The CIEM is intended to be worn exclusively behind the ear.

When choosing the look of my CIEMs, I settled on a black matte shell and a similar faceplate with bunny ears (well, you're not surprised, really) on the left front panel, the model name "XE6" on the right. It turned out, as for me, just amazing: cute and very stylish - I personally am very close to this approach to design.


At the bottom of the faceplate panel fit a replaceable Atom-X module. ATOM (Air Transfering Open Module) venting is a miniature metal cylinder valve that reduces the sound pressure exerted on the eardrum, thereby protecting hearing. It bleeds the airlock that forms between the sound pipe and the eardrum, and also acts as an acoustic filter, which serves to fine-tune the sound of in-ear monitors.

It is appropriate to recall here that the XE6 uses "Tubeless Design" technology. There are no acoustic tubes and separate chambers for drivers in the design.



The sound pipe was covered by a removable metal mesh that protects the IEM/CIEM from moisture and sulfur. Another know-how of the brand is applied here - Rigid Snap Screen. Now you do not need to break the shell to manipulate the protective mesh, just take the tweezers, loosen and remove the clamping ring, then remove and clean or replace the mesh. Although I would still contact the manufacturer in case of a replacement.

Next to the sound pipe is a round port of an open dynamic driver. This is a grill-protected opening that transmits low-frequency signals directly to your ear cartilage. The same KINETIC BASS that you don't hear, but feel!



A little higher, closer to the 2pin connector, you can find another miniature hole, which is connected with the fastening of this connector. RIGID Technologies is a proprietary technology that FIR Audio claims provides exceptional reliability, durability and serviceability for in-ear monitors.

"The most durable 2-Pin connection on the market, rated for 1,000 connections without issue. Fits any 2-Pin standard. Featuring a revolutionary quadrant socket design that prevents the socket from getting loose."



The 26x8 Awg Satin Black twisted cable is made from pure copper and has the catchy name "Scorpion-C Wire". It is extremely light, elastic, nice and high quality, 2-pin connectors, jack L-shaped TRS 3.5 mm similar to Oyaide, the splitter is made in the same style. The cable length is 1.2 meters. When ordering, you can choose other connectors and connectors, cable length, as well as order a balanced connection 2.5 / 4.4mm.


As I mentioned, the XE6 has a hybrid circuit and is built around six drivers: one DD 10mm, four Open BA Driver and one Open Electrostatic Driver.
The "kinetic bass" speaker is responsible for the vibrations in the lowest part of the low-frequency register, one BA is responsible for the bass, its two brothers work out the mids, another BA - high frequencies and ESTAT - ultra-high frequencies.


Xenon 6 technologies are stuffed to capacity. Well, you can sing roulades to design. Before us is a masterpiece, no less! Let's find out why all these technologies were crammed into such a beautiful body. Let's move on to sound analysis.

Sound Impressions

Before listening, the headphones were burn-in for 70-80 hours.
Sound equipment: MyST DAC 1866OCU V.2, Lotoo paw Gold, iBasso DX240,DX300, iBasso 220 MAX, QLS QA-361, iFI iDSD Diablo & iFi xDSD Gryphon.

With all devices, the XE6s sounded great, and their “voice” varied slightly depending on the sound source and the Atom-X modules used.



The sound of Xenon 6 can be described as perfectly balanced, noble, served in neutral-warm tones, with a slightly accentuated area in the lower register, absolutely natural mid-range, and high-frequency ranges.
This is an unusually smooth, polished and harmonious manner of sound extraction, served in an unusually comfortable, correct, studio-analogue form, with a warm "tube" tint. The tonal balance of the headphones is set up extremely competently in an analog manner.

FIR XE6 perfectly convey the volume and depth of an imaginary space: giving out a massive and organic picture with amazing elaboration of timbres and reverbs, convexly outlining the details of the composition, paying more attention to macro dynamics than micro contrast.
This is an unusually lively, dynamic and "ecological" manner. It's amazing how naturalistic Xenon 6 manages to convey the atmosphere of the songs being played!

Even some top models of full-size headphones did not dream of such a sound.
And of course, here we hear only the perfect coherence of the drivers and the complete absence of phase distortion.


The sound character, as you already know, can be tuned a little to your taste with the help of replaceable Atom-X modules. When ordering the CIEM version of the in-ear monitors, an option with a built-in, non-replaceable module is also available. And models of the Frontier series in the UIEM version come with ATOM XS modules.
Let's deal with the classification of modules:
silver - perhaps the most neutral,
black - neutral with a slight addition of low frequencies and deeper bass,
gold - the most bass with a slight accent in the upper register,
red - makes the sound a little more expressive due to a slight accent on the upper middle.

I opted for a black and silver Atom-X, although I think all options are beautiful in their own way.


The XE6s show a wide dynamic range and amazingly capture the volume of an imaginary space, with a sweeping stereo panorama and precise localization of apparent sound sources in space, where every musical instrument and every note played is precisely in its place. These CIEMs build a wide soundstage with amazing depth of virtual space. This is a massive soundscape, rendered in a smooth, neutral, velvety manner with a stark black background and embossed display of audio images in space.

Xenon 6 is able to impress the listener with its temperament, clear articulation, high resolution and extraordinary tonal accuracy.


The low-frequency range is gently boosted, which brings massiveness and depth to the sound and lays a solid foundation for the Mids. The blow is thick, precise and dense, going deep down. The bass is elastic, textured, with good speed. Despite its neutral-warm manner, the bass succeeds everywhere and flawlessly intertwines in the middle register, darkening the background and filling the listening compositions with a clear rhythmic basis, contrast and timbre variety. A clear clap, impact vibrations - everything is transmitted and felt clearly, accurately and smoothly, without hum and encroachment on other registers.
Well, the dynamic driver with KINETIC BASS allows you not only to hear the power of low frequencies, but also to feel them, to feel these vibrations that get under your skin! And no hint of mumbling, only the accuracy of timbres combined with excellent balance.
Where a beautiful and imposing manner is needed, Xenon 6 can gently roll with a pleasant, thick and velvety, charming bass. Well, if there is mass and pressure in the track you are listening to, then hold on: from the very depths of sound, a low-frequency earthquake will fall on you, and even with the presence effect in the form of kinetic bass energy.

Mids are smooth, natural, timbre rich and textured, delivered in a neutral manner. Here, every musical image or sound is clothed in flesh. This is a well-balanced and unusually harmonious performance, where all the elements of the composition are presented naturally, smoothly, large and multifaceted, with amazing accuracy and informativeness. The presentation of the mid-frequency register is simultaneously solid, plastic and extremely detailed. Power and delicacy, emotions and monitoring, drive and academic manners are wonderfully combined here. Every timbre, every vibration of the voice or trembling of the string is transmitted authentically and deeply. The vocal parts do not excite the ear with sharp bursts and do not upset the failures, everything is unusually smooth, natural and unconstrained. This is a well-balanced and at the same time sensitive performance, where all the elements of the composition are presented with extraordinary accuracy, large and multifaceted. It is worth noting the amazing transfer of the volume of imaginary space.

High frequencies are reproduced unusually clean, clear, smooth and harmonious. Their quantity and quality of working off raises no objections. The register is transmitted clearly, without excessive harshness and distortion, without drawing excessive attention to itself, in a completely neutral manner. Highs harmoniously contribute to the overall work, without whims and self-will, they give themselves up for the sake of harmony and balance of the entire frequency range.
Working out the upper register, every sound, nuance, whether it's touching a hi-hat or a cymbal, ringing a bell, everything sounds so clean and accurate that it deserves, in my opinion, the epithet "reference"! Special thanks to FIR Audio for such a polished study of the high-frequency range!


With any musical genre XE6 cope without problems. They reproduce both classical music, instrumental, jazz, electronics, rock, and brutal genres with extraordinary interest.


FIR Audio XE6 - an unprecedented model of in-ear monitors! Thanks to such extraordinary developments, for many years my interest in testing portable Hi-Fi, and in this case, real Hi-End, has not faded away.
Before us is TOTAL CIEM, which audiophiles around the world will dream of and which the audio industry will measure up to. I will say more, in order to create such a masterpiece, not enough talented engineering, you also need a visionary gift. XE6 actually get to the very edge of the studied universe of sound and look beyond it!

Of course, such a technological sound "rocket" sent into musical space has a corresponding cost. You can order Xenon, both in CIEM and UIEM versions, on the official website for $3899. The price tag, of course, frightens with the number of numbers in it, but for the most notorious admirers of the highest category of sound, I recommend without the slightest hesitation to make every effort to purchase the FIR Audio Xenon 6.
A great review? Very informative
Simply put, a stunning unit, which should have all manufacturers reaching for their drawing boards to compete. Instantly at the top of my list, it is. Excellent review as always!
@ngoshawk absolutely agree my friend. Thanks so much 🙏


500+ Head-Fier
Fir Audio Xenon 6 & Neon 4 – Frontier Series Delivers Kinetic Bass with HUGE Sound!
Pros: Huge, enveloping sound with kinetic bass impact
Highly engaging, euphoric tonality
Benchmark dynamic range for iems
Detailed, shimmery treble without fatigue
Extremely holographic, 3D soundstage
Beautifully designed universal shells
Cons: Some may find shells to be on the thicker side
Open bass driver does leak more sound than most iems
Xe6 is a niche set with unique tuning that does not excel with all genres
Atom XS modules are tiny and cumbersome to swap out
Packaging and accessories adequate, but could be better for asking price

Since the Xenon 6 and Neon 4 share the same DNA, I've decided to write a combined review for these iems with a brief comparison between the two. The Xenon is the flagship and the Neon is the baby in the Frontier Series line-up.

Rather than regurgitate the product info for the new Frontier Series from Fir Audio, I’ll provide the following links containing all this good information:

The Fir Frontier Series iems can be purchase from MusicTeck here:

Specs & Driver Technology:

Xe6 Driver Specs:
1x 10mm Kinetic Bass Dynamic Driver
1x OpenDriver Balanced Armature Driver for bass
2x OpenDriver Balanced Armature Driver for mids
1x OpenDriver Balanced Armature Driver for highs (with Sound Reflector)
1x OpenDriver Electrostatic Driver for ultra highs

Ne4 Driver Specs:
1x 10mm Kinetic Bass Dynamic Driver
1x OpenDriver Balanced Armature Driver for bass
1x OpenDriver Balanced Armature Driver for mids
1x OpenDriver Balanced Armature Driver for highs (with Sound Reflector)

Frontier Series Tech:

Fir Audio Tech2.PNG

Build, Ergonomics & Accessories:


The build quality of the Frontier Series is exemplary. The stainless steel shells with tasteful gold plating and glass gold leaf infused faceplates on the Xe6 are absolutely stunning. The silver shells with marbled faceplates on the Ne4 are equally stunning, but my preference is the black on gold aesthetics of the Xe6. I do think these are probably the most beautiful iems I’ve had the pleasure of owning. The shells have a nice heft to them and appear to be very durable, but only time will tell how well the mirror finish holds up.



The shells are much smaller than expected, although a tad thick, with curved edges and ergonomic shape that fits in my ear canal perfectly with no discomfort. Despite two fewer drivers in the Ne4, both iems share the same shell size and shape. Fit is fantastic, even given the added weight over iems with resin shells. The shells do stick out from my ears a tad, but this is par for the course with a majority of multi-driver iems. Unfortunately, I was not able to get a good seal with the selection of stock tips. However, after going to my trusty Azla Sedna Light Short tips, I was able to get a comfortable, consistent seal with the shells flush against my inner ear to obtain the full benefit of the open port kinetic bass driver.

The included 8-core pure copper braided cable is of high quality, but on the thinner side compared to the boutique cables often included with flagship iems. I am not a huge fan of overly thick, heavy cables, so I can appreciate the cable selected for inclusion here. The cable is soft and supple with no microphonics, and includes angled 2-pin connectors and a right angle 4.4mm termination, which I greatly appreciate! I really wish more manufacturers would go with the angled connectors, both at the iem and source side since I really think it is more ergonomic than standard straight connectors. And in recent years, it seems 4.4mm has taken over as the standard termination, so it is nice to see Fir Audio recognizing this. Another small attention to detail that I really appreciate is the fact that the included cable contains 2-pin connectors for flush mounted sockets, which provides a much cleaner look that the recessed socket 2-pin cables that are all too often provided with iems without recessed sockets! Kudos to Fir Audio for getting this right!

As mentioned in the Fir Audio literature found on their website, both the Xenon 6 and neon 4 comes with 3 pairs of ATOM XS tuning modules, which can help tweak the house signature of the iem a bit to help dial in your preferred sound. The silver modules come pre-installed, which are middle ground between the gold modules, which provide an elevated bass response, and the black modules, which tone down the bass a bit and increase the treble response slightly.

How did I know what these modules do and what the differences are between them? Well, I unfortunately did not get this information with the iem packaging itself like you would expect, as it was not included! You get a card mentioning how to properly insert the iems into your ears but there is no mention whatsoever about the tuning modules! These iems include a rather unique ATOM (air transferring open module) pressure relief system to reduce ear fatigue and tweak the sound slightly, and yet no documentation describing the different modules or how to swap them out is included in the package, which is a bit frustrating. Luckily, Google got me my answer and the swap process is relatively straightforward… turn hex key left to loosen and right to tighten, but do so with a steady hand as these modules are tiny!

I completed my review exclsuively with the stock silver modules for two reasons. The first of which is that silver is the “balanced” tuning that I felt would appeal to me most, and the fact that the modules are so small and tedious to swap out that I did not want to risk losing one from multiple changes and was not super confident I could definitively hear changes in tonality between modules anyway due to the time it takes to exchange them.



Overall, the Xenon 6 is an extremely dynamic iem with a HUGE 3-dimensional sound anchored by its impactful, kinetic bass driver and thick, euphoric tonality balanced by a shimmering, highly detailed, yet fatigue-free treble response. It is first and foremost a musical iem, but will surprise you with its technical prowess, layering, and imaging capabilities.

Overall, the Neon 4 is a more even-handed iem with a large 3-dimensional sound (just not a huge as Xe6) anchored by its impactful, kinetic bass driver and euphoric tonality with a forward, engaging midrange that excels with vocals. In the upper registers you get a smooth, yet detailed treble response that is a bit softer and not as attention grabbing as the Xe6. To me, the Ne4’s strength is its showcase of the midrange, coupled with the analog bass delivered by the open ported kinetic driver.



The innovative open kinetic bass port is the star of the show here. The Xenon 6 exhibits an immersive bass experience that is extremely analog sounding and difficult to describe without experiencing it for yourself. The bass is huge, hard-hitting, and extremely dynamic with a natural decay that does not sound bloated, wooly, or too thick. The speed and impact is just right, with ample presence and authority without crossing the threshold into extreme bass-head territory that can dwarf the rest of the frequency response. Sub-bass extends deep, impactful, and visceral to the extent that if you close your eyes, it is like you are at a live show and can actually feel the rumbling. The mid-bass is quite thick, providing a full, meaty, romantic presentation that provides a seamless transition into the midrange.

Neon 4 exhibits a similar immersive bass experience thanks to the kinetic driver, although with a smidge less impact and rumble, likely due to the smaller open port on the back of the shells. The bass again is huge, hard-hitting, and very dynamic with a natural decay that does not sound bloated, wooly, or too thick. Sub-bass extends deep, but is a tad less visceral than the bigger brother Xe6. The mid-bass is still on the thicker side with a romantic presentation, but is not as elevated as the Xe6, which allows the mids to become more of the focus and be positioned more forward in the mix.



The mids exhibit a warm and euphoric tonality that provides excellent texture to vocals and guitars. Male vocals are weighty, musical, and are delivered with plenty of emotion to captivate you lose yourself in the music. The lower-mids transition into the upper-mids with a gentle dip from around 300 Hz down to 1K and subsequent rise to a peak at around 2.5K that is very linear in nature, despite the dip being unconventionally positioned closer to the upper-mid region. The transition is linear and smooth without abrupt dips or peaks, and although there is more emphasis on lower mids than upper mids with the Xenon 6, I do not hear any wonkiness or anything unnatural in this region. Male vocals sound natural, and are positioned neither too far back nor too forward in the mix. Upper mids are smooth and non-fatiguing, with female vocals sounding natural, although a bit laid back and a tad recessed from what I am used to. I found that female vocals were placed a bit too far back in the mix on some recordings, but the more I listened, the more natural it sounded, so it really was not bothersome. Overall, I would still prefer a bit more bite and presence for female vocals, but I’d definitely take this tuning over the overly forward, peaky, fatiguing upper mids you get with many other iems. There is zero harshness or fatigue with the Xenon 6. Overall, the entire midrange is smooth and natural sounding, despite the slightly unconventional tuning.

The midrange of the Neon 4 exhibits a warm and euphoric tonality that really shines with vocals and guitars. Male vocals are again weighty, musical, and are delivered with enough emotion to captivate you get you lost in the music. The lower-mids transition into the upper-mids also follows a gentle dip and subsequent rise, but seems to be positioned such that both male and female vocals carry equal weight to my ears. The transition again is linear and smooth without abrupt dips or peaks and sounds very natural for vocals. Upper mids are smooth and non-fatiguing, with female vocals sounding natural. Vocals are showcased rather nicely on the Ne4, as they are a touch forward sounding and often become the focus, along with that kinetic bass. Despite the forward vocal presentation, I do not detect any congestion in the mids, as everything still sounds well separated.


I feel the treble on the Xe6 is the secret sauce that makes it overall tuning work so well. This iem really is chameleon-like in the sense that you think you are getting a warm, dark tuning tilted towards the low end, then you realize the EST drivers are tuned so magnificently that you get this amazing treble extension that is extremely detailed, shimmery, and airy with zero fatigue. The treble quality is so good that it almost matches the quality of bass from the novel kinetic driver. This is quite a feat! The clarity is superb for being such a romantically tuned, euphoric iem. The crisp, present highs really help bring out details and provide an extremely well fleshed out, balanced sounding iem.

I hear the highs on the Ne4 as adequately present, with good treble extension that is detailed, shimmery, and non-fatiguing. To my ears, the BA drivers handling the treble on the Ne4 provides a softer presentation with more rounded notes than what you get with the sharper transients on the Xe6. The highs are a touch smoother with less air overall so details do not jump out at you and demand your attention like with the Xe6. While it seems the treble here does take a back seat to the bass and midrange presentation, this is by no means a dark iem, as there is enough high quality detail that comes out in the highs that maintains good balance in the overall tuning.

Soundstage, Imaging, and Dynamics


Xenon 6 exhibits a huge, enveloping stage with excellent extension in all directions. The soundstage has a holographic quality that is eerily three-dimensional sounding, like you are there, in person, with the music being performed around you in a massive hall. This has to be the largest stage I’ve experienced in an iem and is well within the realm of many full-sized headphones, which is a huge accomplishment.

Imaging is also the best I’ve heard in an iem. It is very accurate with laser-like precision in instrument placement to the extent that you can clearly hear each individual note with absolutely no hint of congestion to my ears, which is quite a feat for an iem touting a house signature that is thick and euphoric.

Macrodynamics are off the charts on this one. The Xenon 6 delivers such a huge, grand sound thanks to the open kinetic bass port that really puts you there with the music. The insane dynamic range is extremely engaging and demands attention. Despite the overall warm tuning, this is not a laid back iem at all… in fact it is hard to not focus on the music when listening to the Xenon 6 since the highly dynamic nature of this iem grabs your attention and doesn't let go.

Neon 4 also exhibits a large, enveloping stage due to the open ported driver, but the slight forwardness of the mids gives the impression of a more compact presentation that is not as expansive as I hear with the Xenon 6. The soundstage is still well above average, with the same holographic, 3-D quality, just not to the same extent as the Xe6.

The Ne4 also images quite well with accurate and clear instrument placement without congestion, though it is more difficult to pick out individual notes on the Ne4, again due to the less airy, more laid back presentation.

While macrodynamics are still well above average here with a grandiose sound thanks to the kinetic bass port, the Neon 4 is a bit softer and not as energetic compared to the attention seeking Xe6. There is still a very good level of engagement here that I really enjoy, and can really appreciate the slightly laid-back dynamics as this presentation strikes a nice balance between being sleepy and too energetic.


Below are a few notes on my comparison between these two iems:
  • Xenon 6 is more analog and noticeably bigger sounding, with a more holographic, 3-D soundscape.
  • Vocals, especially female, are pushed back slightly in the mix compared to the more up front, intimate vocal presentation on the Neon 4. Overall, Neon 4 has a more forward midrange that, while still very engaging and musical, is not quite as thick and euphoric as the Xenon 6.
  • Xenon 6 has far superior dynamics with better resolution, imaging, and instrument separation. Neon 4 is no slouch in any of these areas, it is just that Xe6 really stands out and is frankly the best I’ve heard when it comes to dynamics in an iem.
  • Neon 4 treble does not have as much sparkle and shimmer as Xenon 6 and is not as well extended, but still not lacking in detail. Ne4 is smoother sounding with less air and sparkle, while the EST treble of the Xe6 gives it a tinge of an analytical nature to balance out the warmth.
  • Bass quality is actually pretty similar between the two, with a very analog sounding powerful bass, but Ne4 is not quite as authoritative or textured as Xe6.
  • Compared to Xe6, Ne4 is laid back with a more relaxing presentation due to its subdued treble and more intimate midrange presentation. In contrast, Xe6 brings more excitement with it’s huge dynamics and attention grabbing presentation.
  • Neon 4 is a terrific all rounder that I feel offers good value in the line-up, while Xenon 6 is the exotic, more niche set, that for me, really excels with rock music.



This is my first experience with a true flagship quality, kilobuck iem and I have to say that I am quite impressed! I have not heard such a huge sounding, dynamic iem with this level of analog bass quality, thick, euphoric mids, and highly detailed, shimmering treble with virtually zero fatigue. Fir Audio have rewritten the script on how bass heavy iems should sound by taking their new kinetic bass port technology and injecting it with EST treble goodness to arrive at an extremely well-implemented, blend of euphoric warmth and high-resolution details that provides a unique tuning that should appeal to most. While I admit, the thicker presentation in the bass and low mids combined with the perceived slight recess in the upper mids may not make the Xenon 6 the perfect all rounder, but as a niche flagship iem, it hits the spot!

It seems like I am bashing the lowly Neon 4, but at almost half the cost of the flagship Xenon 6, I do think the Neon is a terrific way to experience the kinetic bass driver technology and do feel it can compete favorably and even come out ahead compared to similarly priced iems. Many of the same characteristics mentioned above for the Xenon 6 also apply to the Neon 4, just to a lesser extent and not to the supercharged levels you get with the flagship. In fact, I can certainly see some people preferring the Neon 4, as it provides a more laid back, easy listening quality that does a great job of showcasing vocals along with that kinetic bass. Despite not being as showy with its technical prowess, the Neon 4 is quite impressive and worthy enough to stand out on its own merits in the $2k price range for it’s well-rounded tuning anchored by the incredible low-end performance supplied by the new kinetic bass vented driver.


After spending more time with the Neon 4 and swapping to the black Fir modules from the stock silver modules, I have to say that the gap in stage, air, and instrument separation between these and the Xenon 6 has closed a bit, while not really affecting the kinetic bass. Xe6 is still the better set overall, but if you aren't looking for the absolute best in technicalities and prefer a more laid back, relaxed sound, the Ne4 might be your ticket!
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Thank you
After spending more time with the Neon 4 and swapping to the black Fir modules from the stock silver modules, I have to say that the gap in stage, air, and instrument separation between these and the Xenon 6 has closed a bit., while not really affecting the kinetic bass. Xe6 is still the better set overall, but if you aren't looking for the absolute best in technicalities and prefer a more laid back, relaxed sound, the Ne4 might be your ticket!
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with which musical genres could XE6 NOT excel, as you remember in the preface of the "Cons" of XE6?


Headphoneus Supremus
Fir Audio Xe6 (Custom) – An Exotic Listening Experience that Adds a new Tactile Dimension to Sound
Pros: Exotic or God-tier performance, bone conduction that adds new tactile spatial elements plus bass for an entirely new listening experience that you can feel, best-in-class clarity and detail plus bass, full-sized performance.
Cons: Not cheap. 😊

FIRST IMPRESSIONS: Holly hell…that is a big sound!!!

The Xenon 6 (Xe6) is Fir Audio’s next generation of their extremely popular M5, one of the best in-ears of all time when it was launched. However, listening to both side-by-side, there is little similarity between the two signatures other than both reaching exotic performance that puts them above the top-tier. I will undoubtedly keep both to offer two different signatures to enjoy my music library – the Xe6 is more euphonic and 3D with the M5 being more transparent and traditional sounding.

The M5 won a spot in the God-Tier category due to its overwhelming AudioTiers membership phrase and was awarded my “If I Could only have One” award due to its versatility compared to the others in that category. I have a feeling that the Xe6 will gain its spot in the God-Tier category as well once everyone gets a chance to hear it. Yes, we have a tour so that you can hear this IEM as well as the Kr5 and Ne4 in the Frontier Series as well – we want to hear what you think. 😊

Tour: Fir Audio Frontier Series – Xe6, Kr5, Ne4

For those that do not know me, I am active on AudioTiers and HEADFI under the username “Barra” and have been hosting product tours for almost a decade now. During this time, I have been able to hear all the greats and experienced the evolution of CIEMs/IEMs and all the associated equipment. From that experience, I can say without a doubt that Fir Audio has always been on top of all the lists in terms of performance and unique tuning capabilities. I have managed a number of tours for Fir Audio and am very excited to now offer another 2022 flagship tour for the Frontier Series. To sign up and to hear the Xe6, Kr5, and Ne4 for yourself, please go to the tour thread and follow the instructions:

As always, my goal is not to just offer my opinion, but to offer tours so you can hear this equipment for yourself. If you are not already an AudioTiers tour member, please go to and follow the instructions in the “Getting Started” box on the Tours page:

Fir Audio Frontier Tour Kickoff Video

The Fir Audio Family

Fir Audio is a premium CIEM manufacturer out of the US that has a full lineup of premium IEMs and custom IEMs and is a longtime favorite on HEADFI and AUDIOTIERS. Their lineup has always made the top of the charts in performance including the M5, M4, as well as their Five x Five. To learn more about Fir Audio, their new Frontier Series, or to purchase the Xenon 6 from this review, please visit their website at:


The Fir Audio Xenon 6

The Xenon 6 is Fir Audio’s new flagship IEM available in both universal-fit and custom-fit models.



The Xenon 6 come equipped with 6 drivers - one 10mm dynamic driver for lows which is fed into a Kinetic Bass port, 4 balanced armature drivers (1 bass, 2 mid, 1 high), and an electrostatic driver (EST) for the ultra-highs. This differs from the M5 that proceed it on two counts – an extra BA for bass, and the Kinetic Bass port. This is enough to create an entirely new experience. The M5 is rated for 6.8ohms with a frequency range of 10hz - 20 kHz whereas the Xe6 is rated at 28ohms with a frequency range of 20hz -20khz although the Xe6 feels like it would be the one that digs into the 10hz range due to the kinetic feedback.

There are several technologies that are associated with the Xe6 including Kinetic Bass, Atom Venting, Open Acoustics, and Rigid Technologies. I believe that the Kinetic Bass and the Rigid Technologies are the only two new technologies that differentiate it from the M5 with Kinetic Bass being the star of the show. The Atom Venting is a key technology for me as it allows me to turn up the volume more without hurting my ears allowing a more dynamic sound in exchange.

Universal vs. Custom

As you can see from the picture above, the universal build on the Frontier Series is smoking hot – it ever looks better in person. However, the custom options are stellar too – a huge improvement in options and appeal since I ordered my custom M5. You can see how beautiful the results were from my build experience – and yes, the other options were great enough that I often second guess myself having desired a number of available options.

The universal format of the Frontier series all has a heft to them and a nice universal fit where I was able to get the majority of the performance offered by these monitors. While some may have perfect ear canals to get full performance from a universal, I do not so I did experience better performance from the custom version. This may be even more important for a bone conduction design as the tight fit that my custom offered me provides better contact with the bone conduction port which provides me with a lift in the effect vs. the universal option.


Based on the bend I have in my inner ear, I can only use the soft silicone tips to get a good seal, so I have not explored any other options. However, the seal provides great performance from the traditional sound port but does not affect the contact from the bone conduction port which is all about the fit of the universal paired to your outer ear. Therefore, your mileage may vary based on these considerations.


There is not much to say about a custom in-ear other than you can expect to get what you design and those premium manufacturers like Fir Audio put out stellar quality as you might expect. More importantly, Fir Audio has nailed all my custom designs in fit as this is the reason that I go custom…nailed it. Also are choices and ease of design which Fir Audio nails as well. Other than that, most manufacturers create a plastic form-fitting insert other than a very few that do silicone, and we can inspect for bubbles and imperfections which there are none in my Xe6 which is perfect.

The size characteristics change between manufacturers with my Empire Ears being the smallest custom and 64 Audio being my largest with Fir Audio being a comfortable middle. There are advantages to each, but my preference is the size middle ground like Fir Audio with a tighter fit but small enough that I can forget that it is in my ear. I also appreciate the Atom-X venting and how it is seamlessly integrated. Some other manufacturers can make this vent pop out and catch on things which is not a problem here. Venting is important to me as discussed elsewhere so better integration is also important to me.

The design is beautiful having chosen their “Purple Leaf” faceplates as seen below. It was simple to create my design using the interface shown below which is loaded with premium choices and offers a WYSIWYG design flow. This allowed me to see and perfect my choices throughout the process with the flexibility to go back and make changes. You may also notice from the picture that there is now a 2-pin option that was not available when I created my M5 design. This 2-pin option allows me to roll cables now without the need for a unique adapter.


Where there is a big build consideration is in the universal design. The Xe6 metal design is so beautiful that it is tempting for even me to chose this over the custom design to gain that unique build characteristic. However, in the end, when comparing the sound, I am sure that the custom was a better option for me and my signature preferences. It is worth joining our tour just to be able to gock at the build quality of these IEMs.


In the end, I am very satisfied with the design I created and love the nice tight fit that offers optimal sound without the chance of breaking my seal. Even better, I have perfect contact with the bone conduction port offering the best Kinetic experience.



What’s in the box? The box looks very commercial and professionally done…as you might see in a big box retail store. This is getting more common, but I have received many in a pouch with no packaging so I still appreciate a good box experience.


The unwrapped box gives way to a slipcover to reveal a heavy-weight cardboard cover box with your contents.


Slipping the cover off reveals your in-ears along with a Fir patch and some instructions.


Removing the top foam that holds your in-ears, beneath resides your case.


As you can see, the case holds not only your in-ears but has all the required tools held within. Of key importance is that you are provided with three options for your venting system offering a variety of signatures. The effect typically allows you to have the most bassy to least bassy option with a middle ground to choose from.


The Xenon 6 Sound

The name AUDIOTIERS comes from my attempt to offer performance tiers to provide perspective on the various in-ear offerings and the surrounding gear that we are touring. While we have definitely hosted mid-tier and some entry-tier IEMs, we have mostly focused on the top-tier offerings with some mid-tier options for those that don't wish to pay flagship prices. The best of the best are termed exotics for their ability to be unique and stand above the crowd. The top 5 of the exotics are awarded GOD-Tier status. The Xenon is likely to take its place among those 5 GOD-Tier IEMs.

To describe the Xenon signature in a nutshell – it has the character of the Abyss full-sized exotic headphone. There is a clarity to the signature, but it is also euphoric and thick even though that sounds contradictory. While it is not the HD800 sized soundscape, it is large or full-sized in stature offering ease in hearing all the details that it serves up in gobs. While there are finer details like you might find in the HD800 presentation, it is more about sensory details and ambiance – that “being there” experience makes it feel warmer and more tube-like. Where the Xenon 6 stands alone is in the kinetic feedback that offers something new…a sound that you can feel as well as hear. This is different than other bone conductive earphones that I have heard/felt, in that it carries a broader frequency and in a more defined, clearer way that brings transparency with it. You have to hear it to know what I mean, so please join the tour. 😊

Optimizing and Pairing


As I did not find either the Xenon 6 lacking in any area, I did not feel that rolling cables at this point would be a benefit. The stock cable is wonderful and the resulting sound is more than satisfactory. So this optimization section is mainly about pairing given that we have all already made investments in gear that we would like to use with our purchases. My preferred DAPs are the Sony WM1a and the Calyx M as I have sold my AK and other DAPs that were not being used. The Hugo 2 rounds out my setup by offering top-tier performance using my Sony or iPhone as a source. My desktop DAC/AMP is the Burson C3R offering 7.5 watts of pure performance to test the limits of scalability. Based on experience, the C3R wattage scales my dynamic drivers to the extreme but is not necessary for BA-only setups. Here is what I found.
  • iPhone 13 Max Plus: Amazon HD Music is a new app on my iPhone that has improved my sound quality considerably. From the standard Apple Music app, the Xe6 sounds great, but better on my better DAPs. The new Amazon app takes this up several notches and gets the iPhone closer to my dedicated DAPs mentioned below. In fact, the music discovery on the iPhone has made it my preferred method to listen to the Xe6 on the go. Either way, the music sounds full-sized from the iPhone, just more filled out with the Amazon app. But the dedicated DAPs are clearly better overall. I just wish that I had access to the Amazon music app with these DAPs. As mentioned above, the only weakness of the iPhone is that in crowded or dynamic passages there can be some clipping at first. However, for whatever reason, the clipping seems to disappear, and the fullness of the note returns after the iPhone warms up with 15 minutes or so of constant playing. Of note is the need to turn up my iPhone to about 80 to 90 percent volume with the VE EXT vs. around 50 percent volume or less with the Xe6. The iPhone doesn’t feel colored in the signature offering a very revealing look at the Xe6 but may not extend to the extremes like my better sources. Ultimately, I would say that the Xe6 scales up better than it scales down but is extremely good on lower-end devices as well.
  • Calyx M: The Calyx M is famous for its sound quality implying that the 9018 is responsible. While the stats don’t speak to this, the amp is likely to be the bigger influencer burning up a giant battery in less than four hours to meet that quality output. The clarity and transparency offered in the colder Calyx M signature offer more detail than the Sony below. In comparison, I used to like the Calyx M better than the Sony until I got a custom firmware upgrade on the Sony. The Calyx takes the audiophile performance up a notch with more and tighter detail, while Sony can actually be more fun. An advantage the Calyx has over Sony is that volume slider that allows me to perfect the volume for each song instantly and to play the Xe6 louder than normal for short bursts. This is more important for the Xe6 vs. my other non-vented IEMs as the ATOM system allows me to play louder without damaging my ears. The clarity of the Calxy M boosts the detail even more on the Xe6 and the powerful amp boosts the texturing. The M is a great pairing with the Xe6 offering a slightly different signature than the Sony which comes across as warmer and punchier. The Xe6 loses some of the tube-like euphonics on the M offering more clarity and finer details.
  • Sony WM1a: The Sony was almost sold last year as it didn’t pair well with my CIEMs until I got the new custom firmware. The new firmware now plays nice with all my CIEMs. The Xe6 pairs great with the Sony offering retaining its warm tint to its performance with a nice girth to the note and more resonance and textures. The Sony with its superior battery life and UX is my go-to DAP for the Xe6. The Xe6 signature is not colored on the Sony sounding as expected due to both having similar characteristics. In the end, the Xe6 sounds fantastic on Sony.
  • Hugo 2: The H2 takes the experience up significantly on the Xe6 with a better DAC and AMP. The pairing is more in line with the Calyx M but on steroids. The bass comes out more – but cleaner with sharper edges and the fine detail is at another level. With the H2, the sound also gets fuller – more euphonic. However, as with the M, the H2 brings out the clarity/transparency of the Xe6 making it sound faster for more of an audiophile sound rather than the more fun Sony. The problem with the H2 is that it is a stack that is not always convenient, so this is not as normal of a pairing as the Burson C3R which takes it up even another notch given the additional driving power if I have to deal with the inconvenience. The Xe6 performance is significantly improved with the H2 with an additional gob of detail and is a wonderful pairing.
  • Burson C3 Reference: Going desktop, the Burson C3R is my favorite pairing supersizing the overall SQ significantly and in a fun musical way that crushes the Sony. It should also be mentioned that I am employing the Amazon HD Music application as a source and running it through my Sonarworks True-Fi application tuned to my HD800 headphones that work well with the Xe6 signature. Playing through iTunes with True-Fi turned off brings down the sound quality noticeably, so some may consider this a cheat. Regardless, the C3R drives 7.5 watts into the Xe6 and offers a significant boost to the low end with more punch and more clarity. While the C3R is slightly warmer than the H2, not by much. The soundstage also grows with the C3R. A traditional BA configuration such as the VE PHöNIX doesn’t handle the power boost as well having to keep the volume down to 1 out of 100 or it can sound overdone whereas the Xe6 loves the additional overhead to drive the dynamic driver as well as to bring out more detail from the ESTs. My conclusion is that the Xe6 grabs another boost in detail and soundstage with a quicker bass note offering peak performance – it is the best I have heard the Xe6 sound.
Overall, I find that the hybrid/tribrid offerings like the Xe6 sound their best when offered more power overhead and a more detailed, higher-end DAC such as with my desktop setup. While the Xe6 sounds great scaled down to the iPhone, it would be a shame to not let the Xe6 reach its full potential on a desktop system as well.



The comparisons offered below are of the Fir Audio M5 for those choosing within the Fir Audio brand and of Vision Ear’s new PHöNIX and EXT flagships which seem to be the most commonly requested comparisons within the HEADFI community. To compare the custom Xe6 to the other IEMs, we used the sources described in the previous section. My music ranges from EDM to classical to rock to metal to pop to new age and easy listening – yes, I am all over the place. My preference in listening and comparison testing is to play all genres randomly to jolt my senses while getting a wide sampling of music. Here is what I found.

Fir Audio M5

The M5 is very different in signature than the Xe6. What they have in common is a very full-sized sound for a “being-there” experience and ginormous bass that is textured and life-like natural and exotic audiophile performance with gobs of detail. However, they offer this experience in two different signatures. The M5 can be considered more intimate while also having a wider soundstage with intimacy in the vocals and more space between instruments for transparency. The Xe6 of more tube-like romantic while retaining its clarity having more of a 3D involving soundscape with a new tactile feel to it. The Xe6 focuses more on atmosphere and the big picture while the M5 allows you to get up close and personal with the singer. I may be overstating the differences to create a meaningful comparison as they both offer a full experience, but the experience is different. The Xe6 has a fuller stage which makes it feel more compact, but it probably can be better described as round vs. the traditional large width of the M5. What I am getting at is that there is just more information provided with the Xe6 to listen to as it adds atmospheric clues. This additional 3d sense probably comes from that tactile feeling provided by the bone conduction technology. Different from other bone conduction headphones I have heard, the Xe6 seems to bring out a sound that you can feel in the treble range as well. As for bass, they both have that huge dynamic driver, but the Xe6 adds both the kinetic port as well as an additional BA dedicated to bass. While the M5 is no slouch with bass, there is just more information in the Xe6 output. I would say that while they are both fast, the M5 feels faster and clearer than the bass on the Xe6 which adds a lot of atmosphere to the equation. However, the Xe6 is clearly more fun. In the end, the Xe6 and the M5 will both have prominent spots in my IEM library allowing me to have two different exotic performance options to listen to my music library to hear it differently – win/win.


Vision Ears PHöNIX

The PHöNIX is Vision Ears' new flagship in-ear replacing their previous ERLKöNIG flagship. The PHöNIX has already gained a huge fanbase given its exotic performance and is likely to replace the ERLKöNIG in AUDIOTIER’s god-tier 5 lineup. As a traditional BA configuration with 13 BAs, the PHöNIX is easier to drive than the Xe6 which is a tribrid boasting both a dynamic driver as well as ESTs plus a kinetic port which all take additional power. Regardless, both sound wonderful on my iPhone, and both scale considerably on better gear. They are both top-of-the-game, god-tier performers with different signatures to enjoy your music library.

What is different about the PHöNIX vs. the Xe6 is most notable in the bass response. While the PHöNIX enjoys that Vision Ears BA bass mastery, there is no comparison to the much more powerful Xe6 bass which compares closer to the Vision Ears EST while still surpassing the EST given the additional tactile Kinetic port. If you are looking for bass first, the Xe6 wins. However, the PHöNIX is more romantic than the Xe6 which is quite romantic itself. I often make the comparison between high-end solid-state and tube-like tuning where the solid-state has more transparency, faster notes with more contrast whereas the tube-like sound is more akin to warm, lush, and romantic. On that scale – 1 for solid-state and 10 for tubes, the PHöNIX is a 9/10 where the Xe6 is a 6/7, and the EXT being compared next is a 3/4. In the end, both the PHöNIX and the Xe6 are the best of the best with different signatures – the PHöNIX may appeal more to easy listeners and classical genres while the Xe6 will blow the mind of those that love more lively POP or EDM. The PHöNIX is one where you sip fine wine and relax whereas the Xe6 will get you up on the tables to dance. Your choice…


Vision Ears EXT

As mentioned above, this new co-flagship Vision Ears IEM is more solid-state in tuning offering an incredibly transparent experience backed by the second-best bass in the business. While the M5 could share that second-best bass title, it is more of an all-rounder where the bass is not as forward in the signature. The EXT doesn’t fool around, that bass is huge with a 10mm dynamic driver that is only beat by the Xe6 due to that tactile kinetic bass port technology that takes it to the next level. However, the bass is not the full story with the EXT, it is an Elysium plus. The VE Elysium is known for its mids forward signature that is very unique and exotic in performance. The Elysium is my best of the best for mids, but this is the key focus there it is not an all-rounder, but it is my go-to vocals IEM. The EXT adds that incredible bass to the equation offering the full spectrum of sound taking it to flagship status making it one of AUDIOTIERS' exotic class IEMs. These two IEMs are both exotic and offer stellar sound quality. They both offer full-sized sound and an extreme frequency range with the power to drive textures and detail from end to end. The difference is mainly in the clarity focus of the EXT vs. the euphoric richness of the Xe6.

To summarize, the EXT is more solid-state with a lively signature and an extremely awesome bass response, the PHöNIX is at the other end of the spectrum with a more laid-back, rich tube-like feel in comparison, with the Xe6 being somewhere in between with an additional level-up in a 3D atmosphere with a sound that you can feel. The Xe6 is closer to the PHöNIX than to the EXT in terms of lushness but retains that 10mm dynamic bass excitement of the EXT. Again, the PHöNIX wins for easy or traditional listening while the EXT and the Xe6 win for more dynamic genres such as POP or EDM. They all sound wonderful with all genres but have the tools to take their favored genres one step further. So what do you prefer, solid-state or tube-like signatures?


Concluding Thoughts

The Xe6 is sure to wow any listener as a unique listening experience and an easy recommendation for those that can afford it. They offer peak performance checking all the boxes of modern technology and easily reach my exotic performance tier and is a candidate for my god-tier award. The only concern is for a more laidback music listener as this is an extremely energetic IEM that makes you want to get up and dance vs. sit down and sip wine. Regardless, if you live in the US, then you are free to join our Fir Audio Frontier Series tour to hear the Xe6 as well as its lower cost siblings the Kr5 and the Ne4 for yourself allowing you to decide for yourself – the way it should be. 😊
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Do the XE6 and KR5 sound very varied?