Review: FIR Audio Electron 12

Sound impressions

I put e12 through my regular regimen of test tracks, mainly female vocal-driven indie and singer-songwriter tracks, but also modern and classic pop, electronic and EDM, classic rock, and a sprinkling of vocal jazz. 

While FIR doesn’t list sensitivity specs, I find the 16-ohm e12 very easy to drive, in the same ballpark as the two Frontier Series IEMs. Since I found e12 to be fairly source sensitive (more on that later), I chose HiBy’s RS8 as the best compromise based on my preferences, but also in how revealing it is of e12’s tonality. Setting the DAP in high gain, I rarely ventured past 25 on the volume dial, which would probably be considered above average volume for most listeners.

While I mainly used the stock cable and silicone tips for these impressions, I must stress that neither were my preference for e12, and I encourage you to read my notes below on tip and cable rolling. Also, I found that tonality changed quite considerably once e12 was burned in beyond 70 hours, which again is something I strongly recommend you consider doing.   


e12 is tuned with a mild V tonality, with moderately elevated and rather physical bass, a neutral lower midrange rising to an elevated and audibly forward upper midrange, and an even more elevated low- and mid-treble, dropping slightly after a hefty 8-9KHz peak with another small peak in the air frequencies. As such, I find the sound to be very tactile down low, and crisp, clear and very energetic from the pinna gain through to presence.

Bass is probably the star of the show, but at the same time this is far from the type of bass-first presentation I usually go for. Instead of heft, bass is quick, textured, nuanced and very detailed, although if you pick up a fresh e12 with little to no burn-in, you might hear some bloat instead. Sub-bass is nicely extended with delicious rumble, but only enough to preserve the midbass punch, of which there’s plenty. 

Tactile Bass tech is definitely doing something, because there’s a quality to bass-prominent tracks that tends to fill the space with rippling bass notes; I can almost see them reverberating in and around the stage it creates. It’s an utterly satisfying experience, and even though it’s not particularly forward, and lacks the physicality of Kinetic Bass, it’s some of the more enjoyable bass presentations I’ve heard, especially from a single DD.

To experience the scope of e12’s bass quality, start with the drum salvo in Danheim’s powerful Ivar’s Wrath. At around the 47-seciond mark, the track is punctuated with beating, rhythmic drums that ripple with texture, their rumbling decay lingering while all manner of swish and swipe take centre stage. The bass presentation creates a real sense of scale, and the texture e12 is able to evoke adds grit and substance to a very lifelike instrumental performance. 

Moving from bass to midrange, there’s a levelling off – though not quite a scoop – in the lower mids, which I consider fairly neutral. There’s no danger of bass bleeding into the mids, since there’s not enough of it in the first place, and there’s definitely none of the warm afterglow you’d hear in the lower mids from more midbassy sets. Male vocals are well presented, suitably chesty, and very clear, and instrument fundamentals, while not exactly full, aren’t artificially thinned out either.

This clarity and cleanliness is impressive for sure, but this is also where things start to get interesting, especially as we move up the scale to the upper midrange. e12 isn’t shy on upper midrange energy, and while I’ve heard more elevated uppers in other sets, those sets usually have larger bass boosts to offset it. Not so here, so you’re getting a double shot of clarity with a boost of energy, whether you want it or not.

This can, potentially, make some female vocals and upper register instruments come off as shouty, although on the whole it’s very well controlled, and quite easily mitigated with a cable swap and some tip rolling. When I said the stock silver cable wasn’t ideally suited to e12’s tonality based on my preferences, this is what I meant. 

There’s no denying, though, that if you love your upper midrange clean and crisp, with excellent articulation, that’s exactly what you’ll get, even though the flipside is a cooler, somewhat less analogue sound than many would consider musical

Angel Olsen’s iconic Lark, the opening track to her transcendent All Mirrors LP, is my go-to test for upper midrange elevation. Don’t let the beautifully melancholic, softly spoken intro fool you, when Angel hits her stride at 1:19, if her vocal explosion doesn’t blow your ears off and have you reaching for the volume dial, it’s safe to say e12’s upper midrange is just your cup of tea. There’s some scratchiness to the vocals, especially in the intro, that I attribute to the treble peaks (more on this below), but e12 absolutely comes into its own with the textured, impactful bass lines and deep, detailed stage that permeates this brilliant track. 

The same clean, energetic sound continues from the upper mids and up into the lower and mid treble, where a series of peaks are dialled in to both avoid sibilance and boost incisiveness and detail. Depending on your treble sensitivity, you may or may not find the extra energy here fatiguing. On the whole I don’t, but I can’t deny there are numerous tracks, especially those with higher-pitched female vocals, that come off as slightly dry and occasionally raspy because of the sharp highlights in their trailing edges.  

That said, there’s detail aplenty here, and I’m picking up far more subtle cues and layered notes than I would from other single drivers. While you may not necessarily jive with the tonal focus, especially if you’re after a more relaxed presentation – which this is certainly not – you can’t deny the control and precision FIR has managed to eke out of this very impressive driver. 

Listen to Lily Kershaw’s Always and Forever and you might hit on some unusual crispness in Lily’s pristinely silky voice. With e12 there’s a slightly digital edge to the trailing edges of her vocals here (similar to the scratchiness I hear in Angel Olsen’s vocals on Lark), a rasp that’s accentuated by the high frequency peaks in combination with the elevated upper midrange. Put another way, if you’re not hearing any issues in the vocals on this track, you can safely say you’ve avoided the worst of e12’s ‘pitfalls’.  

In some ways e12 sounds more like a hybrid, and even the bass manages to keep up with the speed in the upper frequencies. It certainly breaks the mould, tonally, of what most people expect single dynamics to sound like. There’s not much warmth or fullness, replaced by coolness, clarity and speed; there’s also some brightness, but more often than not just crispness and energy. In fact, wouldn’t classify e12 as bright, but rather more revealing and transparent. 


Staging, as you’d expect from such a revealing tonality, is on the generous side, with good width, depth and height. I wouldn’t call it holographic – there’s not enough upper treble air for that in my opinion – but it’s quite immersive. 

I mainly put that down to superb imaging capabilities, probably on par with those of the Frontier flagships, and as such well above the e12’s pay grade. Layering and separation is also very good, and as mentioned above, I can pick out sounds layered fairly close to each other that other monitors I’ve compared to e12 tend to obscure. 

Resolution is also excellent, lending itself to that rich sense of clarity, even though some of that resolution might be the result of the boosted uppers. Again, this isn’t an overly bright sound, but there’s lots of energy present when the details come rushing out at you, and I personally wouldn’t pick e12 as a set for superfast or aggressive music for my preferences (which suggests those that love this type of music will find a lot to like here).  

Last but not least, the control and nuance results in great dynamics, and a very dark noise floor despite the sensitivity of the driver.

Cable/tip rolling 

If, like me, you happen to hit on some of e12’s upper treble peaks, there’s a few things you can do to tweak it (aside from the more obvious EQ adjustments, which I only use as a last resort before listing the IEM on the classifieds).

The most immediate and audible change you can make is the cable. I already mentioned how great the stock cable is…with Rn6. It’s not great with e12. 

Switching out to an all-copper cable like Effect Audio’s Code23 or copper-alloy cable like Eletech’s Raphael immediately tones down and smoothens out some of those upper treble peaks, and mitigates a lot of the shout I hear in the upper midrange. Both of these cables also add some body to the midrange while slightly elevating the bass, which helps balance out the top-heavy energy better than the stock cable is able to. 

Tip rolling is another technique I use to tweak the tonal response of an IEM, and since I find e12 quite tip-sensitive, this works nicely here. The tip bore has a marked impact on bass elevation, primarily by attenuating the treble. Wide bore tips tend to let in the maximum amount of treble, while perceptibly taming the bass, so unless you want to double-down on e12’s energy, I’d avoid these like the plague. 

The two exceptions to that rule are Eletech’s Barqoue, which, while sporting a wide bore, also manages to smooth out some of the treble energy from most IEMs I use it with. Assuming you get a good seal with Baroques, you’ll also be rewarded with added texture and some fullness from the bass. 

My other wide bore favourite is JVC’s Spiral Dot, which uses pits on the inside of the tip (hence the ‘Dot’) to smooth out treble energy and peaks. It also diffuses the midbass and flattens bass, so you’ll need to decide whether or not the overall balance works for you.

My favourite tips for e12 all come from SpinFit. I’ve had good success with W1, the new Omni, and the classic CP145, the latter of which is my pick if you want the ideal balance of slightly attenuated treble, moderately enhanced and elevated bass, and a clean midrange, all wrapped up in one of the most comfortable tips I’ve had the pleasure of putting in my ears. 

Whatever the combination of cables and tips you choose to go with, be it stock, or a mix-and-match of third-party options, shaping e12’s sound to your liking is not all that difficult or necessarily expensive. In fact, I’d go as far as to say that I wouldn’t personally use e12 if I was limited to the stock options. 

Continue to select comparisons…



Picture of Guy Lerner

Guy Lerner

An avid photographer and writer 'in real life', Guy's passion for music and technology created the perfect storm for his love of portable audio. When he's not playing with the latest and greatest head-fi gear, he prefers to spend time away from the hobby with his two (almost) grown kids and wife in the breathtaking city of Cape Town, and traveling around his native South Africa.


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