FIR Audio E12 Review featured image

FIR Audio e12 Review

In this feature, Marcus reviews the FIR Audio e12 or Electron 12, which is a new single 12mm dynamic driver IEM with Tactile Bass technology. It is priced at $1799.

Disclaimer: This sample was sent to me in exchange for my honest opinion. Headfonics is an independent website with no affiliate links or partnerships. I thank FIR Audio for their support.

Click here to learn more about FIR Audio products that we have previously featured on Headfonics.

Note that this feature follows our latest scoring guidelines which you can find in more detail here.

FIR Audio E12 Review featured image
FIR Audio e12 Review
The FIR Audio e12 is a high-energy dynamic driver IEM with addictive 'bangin' lows and a clean set of mids and highs. It is easy to drive from almost any source but sounds optimal with a neutral DAP or dongle that offers excellent dynamic range. 
Sound Quality
Comfort & Isolation
Slide here to add your score on the gear!37 Votes
Powerful bass response
Easy to drive, scales well with more power
SwapX adds a dash of design variety
Hybrid competitors can sound more detailed
Cooler timbre through the mids
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The FIR Audio Electron 12 more commonly known as the e12, marks the launch of the company’s latest monitor range called the Electron Series. 

This is a completely different lineup of IEMs from the previous Frontier Series of hybrid IEMs which included the likes of the Radon 6 and Krypton 5. Instead of complex multiple-driver blends, we now have a single dynamic driver with the e12 as the flagship, followed by the other recent launch, the e10.

They are also priced a bit cheaper than the Frontier series with the e12 coming in at $1799 SRP and the e10 lower at $1299. 

There is more to the driver in the Electron series with swappable face plates, a new bass performance engineering principle, as well as tried and tested applications such as ATOM internal venting. 

One thing I can clue you in on at this early stage of my review; the e12’s bass performance is unmistakably FIR Audio, and by that, I mean concussive, visceral, and breathtaking. It is a pure basshead’s dream IEM. 

If you want to know more about how I came to the above conclusion then read on for my more detailed impressions and comparisons in my full review below.

FIR Audio E12 Swap X electron faceplates



The FIR Audio e12 uses a 12mm electro-dynamic driver with an internal ATOM pressure system equivalent to their Yellow filter rated at 17 dB for pressure isolation. This is one of their stronger modules for bass amplitude at +2 dB over their neutral silver ATOM filter benchmark. 

Tactile Bass

Wedded to the 12mm driver is a new technical pitch called Tactile Bass Technology. There isn’t a huge amount of information about it but what there is seems to pull from the Kinetic Bass experience from the Frontier Series.

There is no mention of hybrid bone conduction technology for the e12 but rather a marriage of both shell and driver in such a manner as to create a second transducer effect for the lows.

Ideally, this should enhance reverberation and create a similar tactile effect to the lows of their high-end Kinetic Bass models such as the Radon 6 and Krypton 5.

Without going into the sound description, (see page 2), I can tell you that the effect is similar to Kinetic Bass at its best with the lows having the familiar tuning hallmark of a FIR Audio Kinetic Bass equivalent. 

The e12 is rated at 16Ω but as always with FIR Audio there is no SPL. I can tell you it is surprisingly easy to drive from a portable source’s low gain balanced output, more so than their hybrid models.


The e12 can be purchased in either universal or custom IEM format depending on your preferences. The sample I have here is the universal format however, it’s not a fixed design.

The final new feature is an interchangeable face plate system called SwapX. This allows owners to pick their preferred finish for the faceplates from over 37 design options. You can also customize the logos or even upload your artwork to give it a level of personalization.

Think THIEAUDIO Monarch MKIII but on a bigger scale giving you but a small taste of what can be done on the custom design side of the house.

FIR Audio E12 drivers on a white background


The design language of the e12 shells is not that far from the Frontier Series such as the Radon 6 universal. Side by side the e12 has matching housing depth but the shell is much wider making it a much larger-looking IEM.

The shaping is still that lateral teardrop effect with a 3-piece shell, nozzle, and plate, however, the curving on the main shell is not quite as elaborated as the Rn6 universal format. It also has no mesh on the front of the nozzle so pay careful attention to any possible dirt slipping down there during daily use.

The e12 mounting plate, main housing, and nozzle are all cut from machined aluminum and finished in an anodized blue creating a fairly robust and smoothly curved set of shells.

The top of the main shell is finished with a low-profile stem and SwapX 2-pin connector system which seems to be an evolution of the Rigid Technologies socket from the Frontier monitors.

I received two SwapX plate designs which consist of what seems to be a slim transparent resin encasing with a single strong pill magnet attached to the back of the plate. 

The first is called Electron. This one reminds me of an Abalone finish with its aquatic-themed mesh of blues, greens, and black.

It’s the more striking of the two designs with the second a subtle but no less complex mix of sparkling rouge and indigo called Dragon Fire. The latter is a perfect match with the red of the HiBy R8 II sample I have here.

FIR Audio E12 Swap X plug on plate

SwapX Assembly

One thing which I think is clever from FIR Audio is the seeding of some of the thinking behind the Bellos Audio brand with the e12 top plate bed held securely in place with 2 screws.

FIR Audio calls this ‘SwapX Assembly’ with its underlying modular approach similar to the Bellos Audio X2 and X4 models I reviewed previously. They also boast a screw lock system and modular print design for their shells giving the FIR support teams easy access for fast and efficient servicing. 

Since the screws are under the e12 SwapX plates this is a more elegant interpretation compared to the cheaper Bellos units. Unless you take off those interchangeable plates with the supplied suction cup plug tucked away in the carry case you will not see any screws.

FIR Audio E12 beside a red silicone ear tip

Comfort & Isolation

Because they are a bit bigger and heavier than the Rn6, the e12 will create a bit more presence in your ear. The solid machined aluminum will also be a little more rigid in terms of following your ear shape and a bit cooler to the touch on a frosty morning.

However, the fit is fairly comfortable and the level of passive isolation is much better than I expected from a vented universal IEM, especially with the supplied stock foam tips.

The alternative wide-bore silicone tips come close though and are comfier to my ear compared to the foam alternatives. They will produce some changes in the tonal coloration of the e12’s output. If you are sensitive to treble the foams are going to be your preferred route. The silicone tips open up the sound a bit more but create a cooler tone.

The ATOM filter inside is the yellow filter which is the strongest dB-rated filter for isolation at 17 dB. From my previous experience with testing the ATOM filters on the Krypton 5, it is also the most bass-friendly filter and one potential factor in why the e12 does so well with its bass performance.

FIR Audio E12 stock cable on black leather background

Stock Cable

I am surprised to see the guts of the excellent Radon 6 cable make its way down to the e12. This is a balanced terminated 48″ 26AWG 8-wire geometry with pure silver and copper shielding as opposed to the 48″ 26AWG SPC inside the Frontier Series ‘Scorpion’ wire.

This time, instead of the dark, brown-toned braided PVC jacket from the Radon 6 we have a clear PVC finish with a dual conductor twisted finish which lightens the tone considerably and lets the copper cable shine a bit more. 

The finishing to me is more discreet than bold with a nice lightweight low-profile black metal splitter and chin cinch including a matching colored 2-pin connector and branded 4.4mm plug barrels. You will be hard-pressed to get microphonics and memory retention from this cable design.

What I especially like is the subtle additional memory coating for cable shaping around the ear. It is very low profile, almost invisible to the jacket itself so it has a nice soft springy feel and is very comfortable around the ear as a result.

FIR Audio E12 accessories

Packaging & Accessories

The e12 packaging follows a similar look to the Krypton 5 and Radon 6 compact branded black box but with a new white printed external sleeve. And yes, you still get the cool Space Force Patch which seems to be in almost every FIR Audio IEM box.

The core box design is very much in keeping with their company ‘bunny’ branding with a black cardboard box beneath using a simple lift lid design.

Inside, you get the e12 monitors and the cable neatly displayed on top, with the case, manual, and accessories presented inside a deep-layered protective foam underneath.

The case is an elegant black leather puck-style design with the FIR Audio branding on the detachable lid. The case is a bit big to be called pocketable but there is plenty of space for cables, accessories, and drivers.

The internal walls have a soft felt material to prevent accidental damage from moving around. Despite its leathery finish, the frame and base are quite rigid so it is also quite durable for handling.

The e12 carry case also acts as a clever tray holder for the accessories including the tips, cleaning brush, and the SwapX suction plug. And yes, there is enough room for the cable and monitor shells to fit on top.

Click on page 2 below for my sound impressions and recommended pairings.

Click on page 3 below for my selected comparisons. 

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