Fir Audio E12

The e12 is one of the latest additions to Fir Audio’s catalog, representing a new line of IEMs - the Electron Series. It’s a single 12mm electro-dynamic driver construction with a few cool tricks up its sleeves, all at a price tag of 1799 USD.

Introduction to the Fir Audio E12 Review

Reviewed Fir Audio E12

The first time I came across Fir Audio was a few years ago – before I started reviewing gear – when I was looking for some cheapo wired in-ears, frustrated with faulty TWS solutions I had the misfortune of coming across. Of course, I watched some videos and read some reviews by my favorite reviewers out there, and while consuming some of their content, I stumbled across the venerable Fir M5s – back then I thought to myself: “2799 USD?! Who would pay that much for IEMs?!”. Ahh, old days. Now, a few years and a few pairs of IEMs later, experience has taught me, that I would be that crazy person. Dear kids, this is why you shouldn’t expect to get wiser as you get older…

While not my first encounter with Fir Audio, the first time I got to test their stuff for a longer time (about a month or two I believe) was when Paweł lent me Fir Audio’s Krypton 5 so I could make a video about them. That occurrence was crucial in shaping my taste in IEMs, as the Kr5 remains in my top 5 favorite IEMs of all time to this day. I was hugely impressed by Fir’s attention to detail and innovation-oriented approach – Kinetic Bass blew me away with the amount of fun I had while having a listen. The build quality left absolutely nothing to be desired, and it kinda felt like a small Bentley in your ears – that’s how impressed I was by the overall product quality displayed by the Kr5. 

Before I received my pair of Fir Audio E12 to do the review, I decided to take a look at some promo materials to become familiar with what the pair was going to offer. You know, do some homework. One thing I came across was a video in which none other than Bogdan Belonozhko, the founder of Fir Audio, talks about how he’s never been so excited about a product release in his 13-year-long career. That, of course, got me excited as well. Being familiar with Fir Audio’s way of handling new solutions and technological advancements, I knew this would be something special. 

After all, that’s the same way I felt about the Kinetic Bass feature on the Kr5. And I was surprised to learn that the flashiest and most marketable new feature under Fir Audio’s belt had to do with… aesthetics! Boy, I couldn’t wait to test the all-new SwapX tech out. 

On another note, at the beginning of February, I took a trip to the north of Italy, to ski in the mountains of San Pellegrino. Of course, I took my e12 with me, as I need at least ONE good pair of IEMs wherever I go. One day, after receiving the overwhelmingly positive news – I’ve passed the last exam of that semester – I sat down on the patio in a small hotel in Moena, set my Balmoral Anejo XO Petit Robusto alight, plugged the e12 into my trusty old Luxury & Precision W2 and began the listening session while watching the sunset in a delightful orange and purple spectacle, melting over the serene mountains of San Pellegrino. I gazed upon the mountains right as the saxophone started its small rant in “Quarto de Hotel” by Hareton Salvanini. My soul started floating.

And just like that, I created a core memory using one of Fir’s creations. I’ll remember that moment until a social worker hits me with a “Sure you did grandpa, sure you did…” at a nursing home once I get very old. It was a great trip, even though I haven’t stumbled upon wild Gladiator Cables in the woods of northern Italy. I assure you, I’ve tried.


Box of reviewed Fir Audio E12

I was stoked to unbox those and give them a listen, but even despite my utmost excitement, I took some time to appreciate the unboxing experience. Once you remove the white sleeve with colorful e12 on it, you’re presented with a black box with a golden Fir Audio logo and some ornaments. it’s simple, yet elegant and classy. Seeing how many IEMs nowadays, no matter the budget, come with those pesky anime girls on the package, I can’t help but appreciate Fir Audio’s tasteful unboxing experience.

Inside the box, there’s an insert with the IEMs and a cable embedded into the foam. However, that wasn’t the only thing that caught my eye when opening the box. Somewhere inside was a FIR AUDIO SPACE FORCE patch! I love that addition, I haven’t experienced any other manufacturer doing that with their products. that’s genius – you can now WEAR Fir Audio merchandise! Wait…

Another important gadget in the box is of course the case for your IEMs. It’s a round, black leather case, with another foam insert inside – this time it houses your tips, silicone, and foam, as well as some tools – a cleaning tool and a silicone plunger-like device intended for use with the SwapX technology, which I’ll gladly talk about later on. The case can fit all your accessories while also being able to house your IEMs, which is great. I believe this type of case is a usual solution for Fir Audio – if you’ve handled their IEMs before, you’ll know what I’m talking about.

It’s not as sturdy of an option as Craft Ears’ legendary pelican case (I don’t think they can be beaten at this point when it comes to rigidity) but it’s more eye-pleasing, and it’s still a very convenient and safe option. Not once have I feared the case opening by itself or my IEMs being damaged in transit while traveling to Italy. Overall – props to Fir Audio for finding a great balance between IEM safety and sleek design.

Build, Comfort and Tech

The build quality is not dissimilar to higher-end Fir Audio products – the aluminum shells are lightweight and well-fitted, inspiring confidence in the product and making a great first impression on a new user. I, having dealt with Fir’s build quality before, wasn’t surprised by the state of the craftsmanship displayed on the Fir e12, and it’s one of those instances where it’s pleasant not to be surprised. I haven’t heard of an instance where Fir Audio would disappoint with its build, and e12 is no standout. In terms of looks, the design is pretty straightforward, with no inscriptions or multi-color multi-material action going on, apart from the faceplates of course. 

It’s just a well-made solid aluminum shell, clean and simple. The nozzles are quite long though, at least longer than those found on the Svanar. Bear that in mind. The quality feel is not exclusive to the IEMs themselves, however, since the included cable is also of amazing build, I feel like it is an improvement over what we got to see paired with the Kr5. The materials listed on the product page at Fir’s website declare that the 8-braid cable is made of pure oxygen-free silver, with copper shielding. 

Usually, I find myself inclined to immediately make an upgrade when it comes to stock cables (I guess that’s just what Hifiman got me used to…), but this time I felt no such need, and I’m 100% happy with the current cable situation at Fir audio. The one I received with my e12 features a 4.4mm plug, with 2-pin connectors of course. 

A feature of the Electron series that highlights both the company’s desire for innovation and the amazing build quality is the all-new SwapX solution. It allows you to swap your e12’s faceplates easily, all thanks to the use of magnets. Being presented with this solution initially was the first time I felt so excited about magnets, in a somewhat similar fashion to Jesse Pinkman in that one Breaking Bad episode with the garbage dump. Making use of said solution is very easy too, thanks to the inclusion of the aforementioned plunger-like device. You just stick it on the faceplate and pull it out of the IEM. 

With the pair of reviewed Fir Audio e12, I have also received an extra pair of faceplates with a design differing from the stock ones, all packed into a small transparent case, doubling down on the unboxing experience. At first, I was quite skeptical about how this solution would work, longevity-wise. Won’t the faceplates come loose with extended use? 

Won’t they fall out of my IEMs? Over time, however, I have rid myself of all those concerns, as SwapX proved to be a simple and effective solution, scoring a whopping 11/10 on aesthetics in my book. It turns the reviewed Fir Audio e12 from a cool-looking piece of headgear into a conversation piece, receiving several intrigued “Huh?” and “What?” from my friends, with just as many “That’s so cool!” sprinkled in. 

If you know my reviews, you’ll know how high I usually put functionality on my priorities list – I’m glad to say I’m very impressed by Fir’s ingenuity. There’s another reason why I think this solution is genius – if you’re anything like me, you would have trouble deciding on which faceplates to pick, or, god forbid, what custom IEM design you should go with. Well, now it’s way easier to make a decision since you can swap the faceplates to your heart’s content. Now you just have to decide which faceplates to get. Oops… 

The technological advancements don’t end there, however. Each time a new line of products is presented by Fir Audio, it seems to carry a number of new solutions with it. To me, the most interesting of the bunch is Tactile Bass. Basically, it’s supposed to make use of the entire shell to reproduce the bass response in your Fir e12. And tactile it is indeed, but I’ll take on the subject again once we reach the “bass” section of the review. Another piece of tech that’s proprietary to Fir Audio’s IEMs is ATOM Venting – short for Air Transferring Open Module – making its return after being featured once again, last time on Radon 6, and on the Frontier series before that. 

The module’s main role is pressure relief, which is supposed to help with expanding the soundstage, as well as reducing listening fatigue. I’ll mention the soundstage later on, but listening fatigue is indeed non-existent in Fir e12, perhaps partially thanks to the venting system, and partially due to a natural sound signature perfect for prolonged, easy listening. A less flamboyant, yet equally as important, is the focus on serviceability. That seems to be one of the focal points behind the way the e12 is constructed, its purpose being to shorten the repair time as much as possible. 

That feature seems to be supposed to cater more towards professional users than avid audiophiles such as yours truly, as it is crucial to have your equipment working before a show or a set. And though I wouldn’t be able to shake the feeling of something being missing if something happened to my e12, my livelihood would surely not be at stake. 

The comfort of those is great. One of the main reasons why, for me, personally, is the insertion depth. While something like Craft Ears Omnium threads the line between quite deep and uncomfortable for me, Fir Audio e12 has the perfect insertion depth – deep enough for noise isolation to not be an issue, yet still not deep enough to cause me discomfort. If your preferences are similar to mine, and both of us appreciate a more shallow insertion on an IEM, reviewed Fir Audio e12 is a great match. Another major contributor to alleviation of listening fatigue is of course the tip selection. 

Fir Audio includes a range of sizes of both silicone and foam tips, so variety is pretty good there. Whenever I test IEMs, I try to make the experience as relatable to the user as possible, so instead of finding an exotic ear tip that not all people use, I chose to do the testing using the stock tips provided. The size that suited me the best was the medium size of the foam variety. For reference, I use the M size of Final Audio Type E, and the tested Fir Audio e12’s foams fit me just right – I didn’t even need to squeeze the foams before insertion, yet they still managed to provide a fun, yet clear sound. When pairing your e12 with your favorite kind of tips, please keep in mind that the nozzle may end up being quite long in your experience, as it is surely longer than that on something like the Svanar. 

Sound of the reviewed Fir Audio E12

Fir Audio’s focus on comfort and ease of listening in the case of the reviewed e12 does not end with the ATOM Venting technology. That kind of approach is evident in the sound as well. The e12 focuses on a laid-back, slightly warm, and bassy approach to sound, without leaving technical aspects like detail and dynamics behind. 

While it does not provide the most open and snappy presentation achievable, it is no slouch when it comes to a satisfyingly high technical level of reproduction, all served with a not-so-little side of fun and engagement. Overall, the sound of the Fir e12 solidifies the impression that it is a device geared for comfort first and foremost – you can sense it when you try out the SwapX function, when you fit them in your ear, and finally – when your first listening session comes to life. 

Another aspect that is worth a discourse is the debate about whether heightened driver count enhances the listening experience. Softears Twilight, Hifiman Svanar, and finally, the e12, show that that statement is not necessarily true, while doing so at different price points. I feel like the potential of a single dynamic driver is utilized very well here – the Fir Audio e12 presents a kind of sound that doesn’t make me question whether or not a few additional balanced armatures or an electrostatic driver or two would make the listening session more enjoyable. 

I have taken the reviewed Fir Audio e12 as it is, and I have enjoyed it, without ever asking myself what should be changed. If you’ve read my review this far, you already know that when it comes to technology, the e12 is already impressive. No need to complicate things by increasing the driver count. 


The bass of tested Fir Audio e12 is probably the most in-your-face and fun aspect of the sound that these have to offer. The tactility of the bass, combined with its ability to reach the lowest registries is exactly as advertised on the “Tactile Bass” section of the product page. The most notable example was the last time I listened to the e12, and “Mr. Rager” by the one and only Kid Cudi came on. I was reading through some homework with the e12 in my ears, and the depth of the bass that these IEMs have reached during the very low bass note concluding the first minute of the song scared me for a second. It’s like the Fir Audio e12 makes the listener use more than 2 of their ears – the rumble is so strong, it feels like it’s penetrating your skull all the way to the inner ear. 

Apart from the capability of low, texturous, nearly tectonic sub-bass, the low registries shine with their punch and dynamics. One thing to keep in mind though – the presentation is not razor sharp like it was with Omnium and Svanar. This time, however, we are presented with a bass response that, once again, seems geared towards easy listening – it is softer than the aforementioned models. Yet, it doesn’t lack a visceral punch or high-performing texture. One of the more aggressive tracks in my roster is “Satan” by Raydar. I don’t think it’s possible to do justice to those thunderous bass hits and low synths without a very capable bass response, and the e12 does very well in that regard. 

Another thing about the bass – it seems to me that another one of its strengths lies within its versatility. Indeed, it’s very strong, but it comes to their advantage 99% of the time. If one day you decide that it’s time for something more relaxing than a track that could be another one of Hotline Miami’s staple soundtrack pieces, Fir e12 won’t disappoint you either. Dire Straits’ beautiful “Brothers in Arms” song is a great example of how a quite bassy Fir e12 can still provide a tasteful reproduction of the lowest registries, without the whole spectacle falling apart, even in a more serene, cogitative piece of music. 


The best thing about the mids when it comes to the Fir e12 is how natural, smooth, and seemingly effortless the presentation is. One of the first tracks that comes to mind is the immortal classic – “Stumblin’ in” as performed by Chris Norman and Suzi Quatro. I won’t get tired of this song, no matter how many terrible house remixes of it I come across while the radio is on. 

The tandem of the higher-pitched female voice of Suzi, and Chris’ lower, more raspy vocals, together with a dash of strings make for a layered sequence that requires some amazing separation from the Fir Audio e12’s electro-dynamic driver. And that’s exactly what the reviewed IEM provides – the presentation is very tidy, allowing each part of the song’s arrangement to shine on its own. All in a natural, lush, and realistic way, without even the slightest hint of artificiality in the mix.

“Without You”, a ballad originally released by Badfinger, dubbed by Paul McCartney as “the killer song of all time”, has its dramatic qualities especially heightened with Harry Nilsson’s haunting performance. The best thing about listening to it on Fir Audio e12 is how, despite being a quite bassy IEM without a special focus on the high registries, it reproduces the highest notes of Nilsson’s vocals in a beautiful, realistic fashion. 

Some might be inclined to believe that when it comes to mids in a bassy headphone or an IEM, the lower part of the midrange would be the one to look out for, with the upper mids being behind, even lacking in some cases. That kind of an issue doesn’t exist within reviewed Fir Audio e12’s performance. It’s capable of reproducing great midrange no matter its nuances, period. That also confirms how well-controlled the bass is – the level of control amidst its quantity and scale is impressive and doesn’t take away from other frequencies.


The treble in Fir Audio e12’s sound signature seems to be the least prominent aspect of the sound, however, it’s quite evident that Fir Audio decided to leave no loose ends when tuning the IEMs, as it is still on a high level of technical performance. The tuning of the highest registries is far from an afterthought, highlighted by musical pieces with prominent hi-hats and cymbals. Take “For Whom The Bell Tolls” by Metallica for example. The cymbals and hi-hats work almost like a metronome for the menacing guitars and thundering kick-drums, and despite not showing the treble much emphasis, Fir Audio e12 reproduces them with the right amount of authority for them to not get lost among the bassy background. 

That’s exactly when the treble’s dynamics shine the most, and let the listener know that a high level of technical performance is not limited to the punchy bass – Fir e12 is consistent with its high performance from the lowest to the highest registries. Another great example occurs when listening to something fast-paced, like “Keep Your Eyes Peeled” by ULTRA SUNN. A lack of a decisive treble performance would keep this song’s potential at bay. Sure would be a shame, because it’s a good one.

If you want to experience how the Fir Audio e12 deals with something like high-pitched violins, look no further than Henry Mancini’s “Theme from Love Story”. When the violins all come together for an enthralling, almost overwhelming performance, with the highest notes on full display, you will come to notice that there is a complete lack of harshness in the treble. It’s a pretty challenging piece of music – reproducing it without a hint of harshness is not something that every IEM can do. The e12 can, though. It’s a great example of how the lesser emphasis on the treble may present itself as an advantage in certain situations when the violins and vocals strike the eardrum the hardest.


The soundstage of Fir e12 doesn’t present itself as the most spacious – while the overall scale of the sounds is quite amazing, the width of the stage won’t knock you out of your shoes. The limited space is utilized to the fullest, however. Fir e12 takes the given real estate and uses it to highlight aspects of sound such as realistic imaging, a decent amount of air, and a huge scale. As I’m writing this section of the review, a live performance of “Land of Confusion” by Genesis is playing. 

The applause of the fans is very clearly separated from the instruments, which, thanks to their realistic presentation, can easily be discerned on the stage. Here’s where the scale comes into play as well – Phil Collins’ voice seems huge and powerful, grabbing the whole performance by the collar and establishing his position. 

There are situations, however, where the low notes are so immersive that the separation loses some of its proficiency. Whether you like that or not is up to you, but I feel like it does some kinds of music more justice than a huge, separated presentation would. Here’s a positive example – if you like listening to your electronic music live, a Boiler Room performance for example, the realism of the imaging and the stage makes for a fun listening experience – like you’re thrown into the middle of the crowd, while simultaneously being right next to the speaker. However, if you’re into something orchestral that requires some huge staging with the clearest separation and air – you may want to consider turning that Boiler Room back on.


HiFiMAN Svanar

This comparison seems fair to me, as both Svanar and Fir Audio e12 seem like quite a similar duo in many aspects – both are around two thousand dollars, both entail a single dynamic driver, hell, even the materials used are not dissimilar. 

Overall, as a product, I must admit that I like the product presentation and the overall package more on the e12. It provides higher-quality accessories, offers a very clever and efficient customization option, and the cable is miles ahead of that provided by Hifiman Svanar’s package. Comfort-wise, they trade blows – some will prefer the sculpted shape of the Svanar, and some will find themselves fond of e12’s simple and universal shape. Both have a pretty shallow insertion, which I love. 

How about the sound? That’s the aspect where the differences are the most evident. Starting with the bass, both present a cutting-edge level of dynamics and extension, and don’t even get me started on that texture. Which one you like more in that regard will mostly depend on your preference for bass presentation. If you’re more inclined towards snappy and fast bass hits as heard on Hifiman’s latest flagship in-ear, go with that. If, however, you enjoy a softer, more relaxed, yet not at all less powerful low registries, e12 won’t disappoint.

In terms of mids, I find the Svanar to be slightly warmer and more musical, with the Fir Audio e12 balancing the mids with the rest of the frequencies very well. The e12 creates a coherent and balanced picture, not without its magic and musicality, however, the Svanar allows the mids to shine a slight bit more, perhaps due to its overall presentation feeling a bit brighter, with a slightly lesser focus on the bass. Both midrange presentations can be labeled as natural, realistic, and lush. Moreover, both contenders show a certain level of versatility in their presentation – the mids are pleasant no matter the musical circumstance. 

When it comes to the treble, both models are very dynamic and detailed, overall presenting a very high technical level. In terms of the presentation, the Svanar seems, as mentioned before, brighter to my ears. The e12 however seems to aim for something else – the higher registries are wonderfully balanced, cooperating with the rest of the sound signature like clockwork. Like Bonnie and Clyde. Davis and Coltrane. PB & J. You get the point… The treble is not too airy and bright, but it’s smooth, dynamic, and very detailed. It lends itself to an overall sound presentation that is cohesive, without anything seemingly out of place, or unnecessarily accentuated. 

As you know by now, the soundstage of the Fir e12, while not exactly congested, is a bit less spacious than the one found on the Svanar. The versatility and overall capabilities of Svanar’s grandiose staging are most welcome no matter the genre, but it doesn’t make the e12 seem like you’re listening to music in a coffin. Both contenders present a high level of separation paired with imaging capabilities that just make their sound signatures make sense. 

Overall, both are excellent picks, trading blows in many aspects of the sound, both as listening devices, and overall, as products. If you’re forced to pick between the two, then I hope you know what you like – otherwise,  the choice may not be easy for you.

Fir Audio E12 – summary

Fir Audio did it again – it’s not the first time that we have been presented with a fun product, entailing new technologies and solutions, all geared to enhance user experience. And not in a gimmicky way either – they bring real improvements to the table, solidifying Fir Audio’s name as one of the leaders in terms of innovation and variety. Everything about Fir Audio e12 lets you know you’re dealing with a premium product, whether it’s the unboxing, handling the IEMs, or making use of included accessories. 

The inclusion of something equally as simple as it is brilliant – the SwapX technology – has truly swayed me and made a lasting great first impression. It makes me wonder what’s next for Fir Audio and their future models, and what’s in store for us, audiophiles, in terms of customization of our products, at least when it comes to things we can uninvasively alter at home – like the faceplates, thanks to the SwapX technology.

Fir Audio e12 is another great proof of how you don’t need a multitude of drivers to make a great sounding in-ear. Its single dynamic driver handles all kinds of music with grace, presenting them in a more or less appropriate, yet always fun manner. The sound signature may leave something to be desired for lovers of the most spacious sound, or a leaner bass reproduction, however, enthusiasts of heightened quantities of bass with a more intimate yet grand presentation will be overjoyed to test this one out. Whichever of these categories you identify with, I encourage you to give this one a try.


Big thanks to Fir Audio for providing us with the E12 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.