Fir Audio Xenon 6

Fir Audio Xenon 6 is the flagship of the new Frontier Series from this American manufacturer. It’s a tribrid construction starting at $3899.


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.