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FiR Audio’s House of M: The M3 – An In-Ear Monitor Review

DISCLAIMER: FiR Audio and Project Perfection provided me with the M3, M4 and M5 in return for my honest opinion. I am not personally affiliated with these companies in any way, nor do I receive any monetary rewards for a positive evaluation. I’d like to thank FiR Audio and Project Perfection for their kindness and support. The review is as follows.

Our FiR Audio M-series round-up officially begins with the M3: A triple-driver, universal in-ear priced at $1199. As said on the introductory post, this M3 features greyish-blue faceplates with white logos engraved on top, along with the line-up’s sublime, anodised-aluminium shells. It features all three of FiR Audio’s staple technologies also mentioned in that article: Direct Bore Drivers, Tactile Bass Technology and the ATOM pressure release system. Taken together, what the M3 provides is a crisp, clear and punchy sound with tactile instruments, tons of air and, yet, a balance and coherence to its sig as well.

FiR Audio M3

  • Driver count: Two balanced-armature drivers and one dynamic driver
  • Impedance: 16.4Ω @ 1kHz
  • Sensitivity: N/A
  • Key feature(s) (if any): Direct Bore drivers, Tactile Bass technology, ATOM pressure release system
  • Available form factor(s): Universal aluminium and custom acrylic IEMs
  • Price: $1199
  • Website:

This review is a part of FiR Audio’s House of M series and will only cover sound impressions. For the introductory article covering packaging, accessories, build and fit, as well as FiR Audio’s slew of proprietary technologies, click the link here.


FiR Audio’s M3 kicks off the pack with a clean, clear, dynamic response; lightly elevated in air, articulation and punch. The monitor sports a light, quick, open tonality, and derives a lot of its energy from its crisp, sparkly, yet refined treble. This is then supported wonderfully by its thump-y, dynamically-driven low-end, and its centre- and upper-mids finish with great presence to lend instruments the structure they require, and to ensure the M3 maintains a coherent sig throughout. The most obvious colouration would be in its lower-mids, where a bit of that thickness has been scooped to give the monitor tight, quick notes and an airy stage. Nevertheless, it all amounts to a crisp, lively sig that doesn’t lose track of realism too.

Spatially, what I seem to be getting between the tubeless drivers and ATOM is a cleaner, blacker background and an airy, effortless delivery, despite the M3’s punchiness. This is especially true down low, where the dynamic driver doesn’t linger quite as long as one typically would. I find that aids the M3 retain its punch for longer periods of time, because you won’t get dulled by its transients as quickly. And, fidelity-wise, it lends this monitor a more open and roomy sound as well. This is particularly ideal given the M3’s staging, which isn’t out-of-head or theatrical, necessarily. Instruments are more on the forwardly side. But, again, the breathing room the tech provides compensates nicely. And, the M3 ends on a high with its resolution and stereo separation. Instruments are well-formed and well-spread-out for a sound as soulful as it is refined.


Although my initial comment about the M3’s thump-y lows may’ve implied a full-bodied, elevated bass response, that isn’t necessarily the case. It actually settles on the more neutral side in terms of quantity and warmth; in line with much of the midrange, and just behind the lower-treble peak. Instead, what gives it this presence and allows it to contrast against the high-end is its power, physicality and impact, courtesy of the in-ear’s stellar dynamic driver. Kick drums are rounded with great oomph; incredibly-textured and tactile. The same goes for floor toms too. Dave Weckl’s on Oytun Ersan’s Mysterious Maze is visceral and life-like, and so’s the one panned right on the In The Room mix of Gallant’s Doesn’t Matter. This adds a guttural, physical aspect to the M3’s sound and counters the sparkle of the highs nicely; without adding warmth or musk.

Much of this is due to the bottom-end’s frequency curve, sloping downwards from the sub-bass into the mid- and upper-bass; a tighter, more focused slam that doesn’t bloom or bleed as much. Paired with this bass’s stellar extension, texture and clarity, it is as much a treat with acoustic kicks and floor toms as it is with 808’s and synthetic bass lines. The ones on Kendrick Lamar’s Alright, for example, drop very low, and the M3 keeps up all throughout. The ever-panning bass line on Anomalie’s New Space is also a gorgeous showcase for the IEM’s lows and stereo imaging; present and visceral, yet never overstepping the keys. At the same time, there are songs this curve won’t match quite as well too. Jazz arrangements like Sarah McKenzie’s We Could Be Lovers may want that warm, husky bloom to the pianos and contra bass to fill out the track and lend it its intimacy. But, as long as your tastes are in check, this’s a well-tuned, quality, DD bass; a star in the M3’s sig.


The midrange is definitely where the M3 comes off most coloured to me. Again, it has a lower-mid scoop between about 300Hz to 1kHz, which gives its notes that tight, clean sense of definition. It works wonders for headroom and separation; effortless, with pockets of clean air between each element. But, at the same time, it leaves these mids with a lighter, less-than-natural tonality. It takes away a fair amount from those fuller, richer overtones, which contribute to an instrument’s weight. This, in particular, affects male vocals. Robbie Williams on I Wan’na Be Like You comes off a tad restrained; lacking dynamics on the lower-half of his voice, which deters the playfulness he’s trying to exude with his performance. This isn’t the most ideal tonality for saxophones either. Amber Navran’s solo on the Jacob Mann Big Band’s Baby Carrots should be fuller and richer. And, the brass section on Snarky Puppy’s Grown Folks, to me, also feel a touch unbalanced; higher-tilted.

But, with all that said, there is tons to love in this midrange’s clarity, definition and presence higher-up the range. Female vocals, in particular, are a highlight on the M3, especially those with lighter, wispier timbres. Carly Rae Jepsen and Taylor Swift will fare better than a Rachael Price, for example, because of the reasons outlined above. Nevertheless, what they’ll all gain from this M3 is striking amounts of detail, along with a bright, vibrant delivery too. These aren’t vocals that’ll ever get lost in the mix, and it’s an ideal in-ear with genres like pop, where you want both the vocals to lead and tons of space for the instruments around them. Records like Grace’s FMA and Tori Kelly’s Unbreakable Smile come to mind. And, further aiding this is the M3’s strong vocal definition. Leads are crunchy and well-realised, and fairly textured as well. So, again, it is a lightly-biased midrange. But, if you like vocals light, vibrant and clean, the M3 will provide with fair technique to boot.


The M3’s treble, to me, treads between natural and crisp very nicely. It’s articulate with a good tick, which is indicative of a 5kHz peak. But, it’s measured and refined as well; never allowing those transients to leapfrog the mids and lows. Now, to my ears, it can still show the occasional bright spot. Listening to Nathan East’s Lifecycle, there’s the tiniest hint of sizzle on the horns, as well as the ride cymbal. Though, it’s not the kind that comes off harsh or metallic in any way, so it’s more so a tonal colouration than any sort of real flaw in the tuning. That bite does fare better in genres like pop and hip-hop, and it also aids separation within this M3’s space. Heading towards the mid-treble is a steady, linear drop, which ensures that that slight bite doesn’t get overdone to the point of brittleness. The snare and hi-hats on Carly Rae Jepsen’s Boy Problems are hard-edged without glare, for example. Those open hi-hats on Snarky Puppy’s What About Me similarly aren’t splashy.

In the upper-treble, the M3 continues that balance by nicely levelling off; adding sufficient air and openness to the image without treading towards brightness. Instruments, though still on the snappier side given the laidback lower-mids, do not come off razor-thin. Plus, this in-ear’s backdrop remains mostly uncoloured too; neither brightened nor over-aerated for that faux sense of clarity. Cymbals and hi-hats trail off smoothly, and it simply comes off realistic in tone for me. In terms of extension, the M3 performs fairly decently. It isn’t rolled-off by any means, though it’s certainly the weakest performer relative to its siblings. Instruments don’t hold their places within the space as solidly as the M4 or the M5, and it does not expand the furthest either. Again, though, assumedly because of the tubeless drivers, the M3 can still pump an immense amount of openness and air into its stage. So, though imperfect, it’ll still output great clarity, separation and cut for most.

Who is it For?

To me, the M3 is an in-ear I’d pick-up if I was after clarity, air and contrast without straying too far from what I’d consider natural or balanced. It’s a monitor coloured for a slightly drier, crisper tonality and a bias towards higher-pitched sounds, but not to the point of plasticity, hollowness or artificiality. Personally, along with its dynamic lows and slightly-forwardly upper-mids, it’s an IEM I’d take with genres like modern pop, along with more electronic brands of jazz-fusion. Musicians like Anomalie, FKJ and Jerry Folk come to mind, along with vocalists like Billie Eilish or Tone Stith. I would not recommend this M3 for those with fullness, richness and warmth listed as their top priorities, or those with Michael Bublé, Laura Fygi and Ruben Studdard at the top of their playlists. Still, I see it as a mid-tier mainstay, with a couple aces up its sleeves too.

Select Comparisons

64 Audio A6t (USD 1299)

Compared to 64 Audio’s A6t, this M3 is a much lighter, leaner-sounding IEM. The latter’s low-mids are considerably more recessed, which results in a drier, more analytical midrange presentation. Then, its elevated low-treble lends transients a brighter, crisper feel as well. This gives the M3 the lead in airiness and separation, but at the cost of its warmth and tonal accuracy. It emphasises snare cracks, bass slaps, lip smacks and hi-hats with great clarity and punch, but it’s not as linear or natural-sounding as the A6t, which tends to be more even between articulation and body; less flashy. Vocals are fuller, warmer and better-rounded, and the same goes for most melodic instruments, really. So, as always, timbre will certainly be up to your use-case and personal taste. Though, in terms of raw coherency and balance, I’d have to give it to 64’s A6t.

Technique is where I think the M3 takes that edge back from 64’s A6t, with tiny leads across the frequency spectrum that add up to a more immersive, open sound. Firstly, the M3’s dynamic driver lends its lows a more palpable, visceral punch. Despite the more neutral presence, the physicality and impact it brings to the table ultimately inches it ahead of the A6t’s in terms of realism and drive. In the midrange, tonality aside, the M3 does manage to eek out a hair more resolution and focus, which helps instruments pop and feel more tactile. The A6t, if unaided by a mid-biased chain, can lack a bit of zing here. Finally, the M3’s highs extend further to my ears, which hugely aids dynamic range. It’s not as prone to feeling boxy or compressed as the A6t, so it’s more ideal for long listening (given you enjoy its sig, of course). That extension gives the M3 a freer and – especially – taller soundstage as well. So, that will be another point of consideration between these two.

Custom Art FIBAE 7 (1100 EUR)

It’s a bit of a similar story with the M3 and Custom Art’s flagship FIBAE 7. The former is a lot tighter and crisper-sounding, while the latter comes off richer, fuller and more natural in tone. That is especially so in the midrange, where the FIBAE 7 – somewhat like 64’s A6t – capably balances articulation and warmth, while the M3 goes all-in on cut. Listening to Snarky Puppy’s What About Me, the horns on the FIBAE 7 are weighty and well-rounded, while the M3 noticeably emphasises the honky-er, brassy-er qualities of these instruments. There’s a lot more air in the latter’s soundscape as well, courtesy of its tightened, compacted notes. But, again, this’ll be at the cost of linearity and coherence, which is more the FIBAE 7’s forte.

Spatially, the M3’s significantly-elevated treble and neutral low-mids give it the airier, more open stage. Notes are further separated, and they leap further off of the backdrop as well. The FIBAE 7 is thicker and mellower-sounding with, again, a much bolder, more intimate midrange. You’ll be able to glean more detail out of the M3’s tighter, more clinical mids. But, again, I suspect it’ll more so come down to a preference in either’s tonality. In resolution, stage size and imaging, the two come surprisingly close. The M3’s tighter notes do make its imaging a tad tighter, but it isn’t by much. Ultimately, the one edge this M3 has over the FIBAE 7 is its dynamically-driven bass. It moves air in a more realistic, palpable way, which aids instruments like the kick drum. So, again, to me, it’ll come down to your tastes in both overall timbre and bass response.

Lime Ears Aether R (1200 EUR)

Compared to Lime Ears’ Aether R, the M3 is, again, quite brighter and sparklier, especially along its lower-treble. Cymbals and hi-hats are sharper-sounding with a more pronounced sizzle, while they’re softer – more diffuse – on Lime Ears’ IEM. The same can be said on the other end of the spectrum, where the M3 produces a more present, impactful bottom-end; most so in the sub-bass. And, in the midrange, this Aether R’s centre-mid elevation hands it a meatier, more wholesome, more substantial tone. But, it drops off higher up the range, which lends the M3 an edge in presence and vibrance when it comes to female vocals or horns, for example. All this amounts to clear audiences for either profile. The M3’s punchier, contrast-y sig is geared for artists like Anomalie and FKJ, while the R is more versatile at the cost of sounding a bit flatter.

In terms of technical performance, the Aether R and FiR’s M3 do trade blows somewhat. The former, to my ears, sports a blacker background of the two, along with greater dynamic range. Instruments aren’t as aggressive as they tend to be on this M3, and you’re able to discern ebbs and flows in a track’s loudness and energy better too. Ironically, given what I just said about the M3’s tone being better-suited for an artist like FKJ, I find the Aether R better reproduces the dynamics of a track like Go Back Home; properly highlighting the contrast between the quieter and louder sections, and giving that song more movement. Spatially, the Aether R is capable of a bit more depth, given its lightly-withdrawn transients. But, the M3 does have the more vivid, direct and lively-sounding instruments of the two, and this clarity may be something you value highly. So, again, both IEMs do have their respective strengths and weaknesses. As always, it’ll be up to what you’re after.





Church-boy by day and audio-obsessee by night, Daniel Lesmana’s world revolves around the rhythms and melodies we lovingly call: Music. When he’s not behind a console mixing live for a congregation of thousands, engineering records in a studio environment, or making noise behind a drum set, you’ll find him on his laptop analysing audio gear with fervor and glee. Now a specialist in custom IEMs, cables and full-sized headphones, he’s looking to bring his unique sensibilities - as both an enthusiast and a professional - into the reviewer’s space; a place where no man has gone before.


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