FiR Audio M4


Headphoneus Supremus
Firry you wascally wabbit!
The oft promised but delayed multiple times M4 review is here! First a UPS delay in getting this to me from France, then a trip to FiR for a grill repair, and finally a delay over the Christmas holidays (I got the wrong priorities, I know, y'all told me that enough). Then another minor readjustment to play around with volume. While FiR didn't officially drop their mascot Firry until the release of their EDC 5x5, I think it's oft to make a reference in the title here. While Elmer Fudd may have been utterly befuddled and exhausted chasing around Bugs Bunny all day, Firry does not. If anything Firry leads you around on a musical energy that you come out of refreshed and ready for whatever 2020 part 2 wants to throw at you.

I've always been weary of dipping into brands that have a small selection as the price of entry tends to be higher either by virtue of the tech being expensive in production costs or simply a cash grab at times. Initially FiR fell into that category (a lack of reviews for the longest time wasn't helpful either. Also we do not talk about my blind buys!) despite being started by a Belonozhko of 64 Audio fame (and we know how I feel about 64 Audio ....and Empire, No those are not love letters to Vitaly and Jack!). My interest was piqued by the comprehensive review that @Wyville dropped and cemented by @Deezel177 's series about their line up. Either way, I would be getting mine second-hand as I this would be a blind buy. At the time I had obtained the Andromeda 2020 recently and despite my initial impressions, I really didn't see it being something I would listen to in the long term alongside the DMagic and MEST (Which I shortly moved after getting the Odin). So up the Andro went while I searched for an M4 to show up. @Fabaaroan eventually reached out for a trade via PM and the rest is history. Before boxing it up to FiR for the repair, my short time with the M4s impressed me. This was only the second fully tubeless design after the Trio I had heard, but it definitely my belief that open hat BAs and acoustic chambers is a direction iems should be going while estats mature as tech.

First things: the shell. I'm on the fence on whether manufacturers should stop using acryclic shells once you get past the $2k price point. I understand durability and all that, but it's going see increased signs of wear in comparison due to the weight and the shells crashing together more often, then there's the increased weight that may affect the fit or whether it'll fall off you ears. The though of the internals banging into a hard shell really does worry me sometimes. That said, the driver count is a huge factor and in models with lower driver counts this becomes less of an issue for me (Andro and Trio come to mind as well in that vein). I've always had an issue with the fit of the u12t and I wasn't too sure whether the M4 would be an issue in this area as well since the shells looked very similar. To my surprise, it did not. I put it in my ears and it....just stayed there. Not even my problematic left ear could find a complaint. The stem itself is not as angled as the u12t and I suspect in comparison with a lower weight due to a much lower driver count resolved the issues I had with the 12t before I even started to listen. One box ticked! I also have to mention that these have nozzle lips! Double lipped as well ensuring a very secure fit on tips. My second biggest complaint with the 12t was the lack of a lip to hold on to tips, having tips coming off in your ear is no fun. FiR seems to be taking feedback in their designs as well. Colur me super impressed!

Testing thoughts and so on:
Onto source: For consistency's sake, the review is based primarily on my 1A in 3.5 on low gain with variable volume (more on that later) and compared on my RME ADI 2 in case power was an issue(This is a new step I've been doing). As my impressions are based on the stock cable where possible and my Scorpion-C was 3.5, I opted not to do the impressions with my PWA Monile which is paired with the M4 on the 4.4. I'll do a small blurb on the effects of this pair up as well.I found the Radius Deepmounts in small to be a perfect fit and those have stayed on there straight out of the box. The last thing is the variable volume, I mentioned here a week or two ago that I was playing with the volume. Whereas with all my prior iems I had the 1A at one volume and stuck with it, I found myself changing the volume up and down depending on song with the M4, a very interesting point, but I found adjusting the volume actually got me more enjoyment out of a track as opposed to a consistent volume.

The M4 leaves no doubt that the bass is DD unlike some select implementations. There's plenty of power and physicality to go around and the slam leaves a crap eating grin on my face whenever I put this wabbit in my ears. The clear subbass bias in the tuning establishes the M4's credentials in the subbass extension area and suit's my bass preferences to a "T". While not as fatiguing to my ears relative to midbass biased tunings, the M4 is by no means tame in that area. Rather it allows the M4 to showcase it's chops in the subbass which isn't allowed to shine as much with a mid bass bias. The bass is well controlled as a coherent whole with a bass shelf that prevents bleeding into the mids, while normally the end result is a slight recession in the lower mids the slightly warm and good body of the bass as whole prevents that from happening and shores it up. I'm happy to say that this is the latest in a line of hybrids where I haven't picked up any coherency issues. My biggest compliment though is for the feel and positioning of the bass on the M4 which always feels to in the exact spot it's meant to be. While the Tactile Bass might come across as marketing, I feel that this is a huge contribution to this feat. It definitely is more tangible to test when you compare to say the MEST's BCD.

This is where it gets really interesting: As those of you that have heard the Trio/Fourte can attest, even if it's a single BA driver, tubeless mids truly sound magical. I would describe the M4's mids as slightly recessed though not as much as the u12t. They're not as full as some would like, but the ease with which the M4 provides separation,clarity and accuracy without losing musical coherency is something that needs to be emphasized. As a result of the tuning, the lower mids have a slight recession, but the slight warmth and body of the mids more than makes up for that. For those of you that have been disliking the upper mids bias tunings, the M4 is a good choice, it's very similar to the u12t and tastefully done. At the same time it more than satisfies the needs of an upper mids manaic like myself. Vocals male and female both come across clear and balanced and are treated equally with no bias. Some may find the vocals too recessed if forward mids are your thing. I normally prefer to enjoy my songs as a cohesive singular presentation rather a bias towards one of the ranges, but the M4 is prefectly capable of having the vocals carry the entire song, in fact I find myself getting lost in the vocals often during my sessions with the M4.

Fir tops off this iteration of Firry with a very well extended treble, overall treble is natural and airy. Sparkle is well executed and balanced, I never had an issue with too much sparkle even when dialing up a Galaxy Supernova. With the exception of a lower treble peak that may bother some of you (No issues here with Firry myself), I really can't find fault with what is essentially Tia treble. It's not as smooth and dark as the u12t and injects some excitment and air into the presentation in comparison making for a much more enjoyable listen in terms of musicality.

PWA Monile Pairing:
With most comprehensve reviews of the Monile only surfacing recently (@Dezeel 's dropped a day after I bought mine from Musicteck), I bought the Monile on a whim based on the limited feedback available in hopes of tweaking my "biggest" concern of the M4: the forwardness of the mids. With the Monile as the permanent cable on my M4, it's safe to say that worked out. The bass and treble have remained relatively the same, with the mids being bought more forward it brought a bit more of musicality. I actually found the M4 being more prone to volume adjustments between tracks than with the Scorpion C. A concern I had with the extruded mmcx sockets on the M4 was actually not an issue. Compared to extruded 2 pin sockets, the difference is miniscule and I had no issues with looping the Monile over my ears.

Bonus Round (Stole this from Cinema Sins)U12t Comparison:
If anyone watches CinemaSins on Youtube, they do a bonus around every now and then. So I figured it was appropriate to nab this for this specific section. Like many a(n) u12t fan (probably all of them), after discovering DD bass desired a hybrid with the mids and treble of the u12t. @Wyville drew a lot of similarities and @twister6 teased that with his infamous picture. So naturally when I did get my hands on the M4, it would be u12t comparisons all around. When you take look at the FRs of the M4 and the u12t, they're eerily similar, but when it comes to actual listenig, the differentiation becomes more clear. So the million dollar question: Is the M4 a combination of the u12t's mids and treble? Yes.... and no. It comes eerily close in the bass and mids, but draws a bit apart in the treble. The M4 is more like a DD with the u12t's mids and treble tuned for musicality. It compliments the more technical and professional sound of the u12t rather than be a hybrid version.

The M4 is an interesting proposal: A setup like the 64 Audio Fourte but at half the price. Having never heard the Fourte (I hope to one day), I can't say how the 2 compare, but it speaks for how far fully tubeless designs have progress with the trickle down to "lower" priced models. Granted it took a spinoff from the company not called Sony (M9 is tubeless iirc?) for this to finally happen. It's a U shape signature without that notorious lower mid recession that plagues iems with this tuning allowing it to be a contender for the elusive all-rounder category that I've been seeking myself (KuroKitsu, you have the Odin and A12t though? Yeah but....). I'll let some other respected gents in the community speak for me here:

@Wyville said " I can’t really fault the M4. Contenders in the category “desert island IEMs” (if you can only bring one set)? I think so."

@Deezel177 also adds "...FiR’s M4 is a strong all-rounder that leans towards articulation and clarity, but remains largely, impressively colourless as well."

I'm inclined to strongly agree with both of them The M4 has a strong technical foundation that shows but with a mind for fun compared to other technically inclined iems. It doesn't strike a compromised or a "balanced" tuning, it has an excellent technical chops AND it sounds musical. The fact that I've considered the M4 to be the "endgame" before circumstances got me in my current "predicament" with the Odin and others speaks monumentally to this. And for FiR to drop something like this as part of their debut setup? Bravo FiR, chasing this wascally wabbit has been fun and not fatiguing in the slightest. Looking forward to the other Firrys joining your stable in the future!
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New Head-Fier
FIR Audio M4: the sound hyperrealism
Pros: Sound, ergonomics, design, workmanship
Cons: MMCX connectors are not the best solution in my opinion.
FIR Audio M4: the sound hyperrealism

Hi friends!

I am glad to inform you that today we continue our acquaintance with the line of in-ear monitors from the American brand FIR Audio! Today our guest is the second oldest model, if you count from top to bottom from “M5”, which has already caused noise in the audiophile environment - FIR M4.

Like all IEM / CIEMs of the FIR brand, the M4 has a hybrid design: here, as you might guess from the model name, there are four drivers (1DD + 3BA). In addition, there is an integrated Atom-X module inside and a unique "Tubeless Design" enclosure design. This is a patented FIR Audio technology in which they have managed to eliminate acoustic tubes as well as separate driver chambers. In such solutions, the most accurate calculation is necessary for the correct location of all audio components inside the IEM / CIEM, otherwise re-reflections and resonances cannot be avoided. But the FIR company with honor bypassed all the "pitfalls" and gave an excellent result, and for that it has a special respect.

I understand that with the current, not quite healthy pursuit, organized by a number of brands and their marketers, for the number of drivers in IEMs and the desire to "stick more inside a small box", in a small IEM case, the number four may seem modest, but I assure you , do not jump to conclusions. After all, the recipe for good sound is not in the number of drivers, but in quality, skill, technical literacy, implementation and, which is very important, taste and understanding, the feeling of sound by the manufacturer himself. And the FIR M4 proves it convincingly!

Well, if after this review you will be interested in other FIR Audio developments, then on our website you can also get acquainted with their M5 and VxV models.


3D-printed metal shells
4-driver tubeless system (1 x dynamic driver, 3 x balanced armature drivers)
Range: 10Hz to 20kHz
Impedance: 6.4ohms
Сable 1,2m, with MMCX connectors

Unlimited Sound: CIEM or IEM?

Before starting the review itself, it is worthwhile to dwell on the fact that in-ear monitors of the FIR Audio brand can be ordered in both universal (IEM) and custom (CIEM) versions - the choice is up to the buyer. The exception is the VxV model, which is produced exclusively in the IEM body.

Well, for those who have not yet encountered CIEM, I can assure you that the procedure for ordering individual CIEM is not at all difficult. You need to go to the website, register, go to the "Designer" menu, select the desired model, its design (appearance, connectors, cable length) and pay for the purchase. Then you go to the hearing center, make impressions of the ears there and send them to the manufacturer. After that, look forward to the arrival of your exclusive CIEMs.


In our case, the M4 model is made in a universal design. And now it's time for us to go directly to the acquaintance with this four-driver miracle!

Appearance kit and ergonomics

M4 comes in a small black cardboard box. On its front side, in gold embossing, the FIR Audio company logo is depicted in the form of protruding bunny ears, from which sparkling sun rays scatter in all directions. Nice, perky and tasteful, well done!



In the box we find IEM encrusted in a foam base with a removable cable (MMCX / 3.5 mm) already installed, a stylish black leather case-washer with an embossed brand logo, intended for storing and carrying in-ear monitors, instructions, a warranty card and interesting colorful stickers ...

Inside the case neatly fit 4 pairs of silicone and one pair of foam tips, as well as a brush for cleaning sound pipes.




In general, the kit is from the category "everything is here and a little more."

The elegant black M4 IEM shells, including the aesthetic champagne faceplates, are made of aluminum. On the left faceplate, we again see perky protruding bunny ears, on the right - the name of the model "M4".

Everything looks very nice and stylish - this approach in design is very close to me personally.

The elegant teardrop-shaped IEM housing is lightweight, durable and extremely comfortable. It is smooth and tactile to the touch. The straight sound pipe is covered with a metal mesh that protects the IEM from moisture and sulfur. On the upper side of the shell there is a connector for a removable cable. Next to the connector are two tiny holes: an integrated Atom "Air Transfering Open Module" and a compensation hole for setting up a dynamic driver. It is pertinent to recall here that the M4 uses "Tubeless Design" technology: there are no acoustic tubes and separate chambers for drivers.
The ergonomics of the headphones are great. Wearing expected behind the ear.



Coffee-colored braided cable made of silver-plated copper litz wire. It is glossy, elastic, MMCX connectors, with a 3.5mm TRS jack and a splitter in the same style. The cable length is 1.2 meters. If you wish, you can replace the cable with any other with MMCX connectors, although personally I find it very pleasant.


As I mentioned earlier, the M4 has a hybrid design and is built around four emitters: three (BA) and one (DD) with an integrated Atom module. Here it is necessary to clarify what the Atom-X is - it is a metal cylinder-valve that acts as an acoustic filter for fine-tuning the sound of headphones. It also releases the air lock that forms between the earpiece and the eardrum. This way, the pressure on the eardrum is reduced and our hearing is not exposed to any risks. In the universal IEM shell, the valve is built into the headphone structure. We have the same case.

Perhaps the only thing I would find fault with is the MMCX connector. In my experience, such a decision often caused disconnections, although, of course, I understand that the company wanted to please many audiophiles who like to play with their collection of cables. But then why wasn't the more reliable 2-pin connector chosen? Moreover, FIR Audio has its own wonderful RCX connector / connector that they install in their CIEMs, and personally I really like it. I think that soon the universal version of their in-ear monitors will move completely to the new RCX. However, these are just my quibbles and it is worth seeing how the MMCX connection behaves this time.


Well, the kit, appearance, workmanship and ergonomics of these IEMs evoke extremely positive emotions in me, but, of course, we gathered together mainly to experience the main magic of the FIR M4 - let's move on to the sound!

Sound impressions

The listening was carried out on the equipment: MyST DAC 1866OCU V.2, Lotoo paw Gold, iBasso DX220 (AMP7), iBasso 220 MAX, QLS QA-361, iFI micro iDSD BL and iFi ZEN DAC + ZEN CAN.

Initially, FIR M4s were burn-in for 40-50 hours.

With all sound sources the M4 sounded good, their "voice" varied slightly depending on the sound source and the tips used.



I highly recommend choosing tips responsibly, as they make a significant contribution to the sound image of the M4.

There is another important feature of the M4. The sound of these IEMs is decisively dependent on the power of the sound source. The better the audio path and the more solid the amplifier, the more M4 is able to show itself in all its glory.


The sound of the FIR M4 is clear, well-balanced, open and unusually melodic. This is a light U-shaped frequency response, with a neatly accentuated subbass area, and light, elegant emphasis in the high-frequency register. These IEMs demonstrate excellent dynamic range and stunningly convey volume, and in it the localization of apparent sound sources in space: higher-lower, further-closer - clearly and scrupulously building a virtual "sound stage".

This is realized so skillfully and at the same time artistically that you no longer just listen to music, but begin to see every sound in the enchanting three-dimensional image that appears in your head. The immersive effect is such that at times it seems that you can touch this or that musical instrument and even the sound itself flowing from the instrument.

I called this sound magic the M4s do "sound visualization!" When musical images are built, as if in a picture of hyperrealists, with crazy detail, amazing volume, extreme harmony, layering, giving out excellent melody at the output. This is somewhat reminiscent of the sound of a studio monitor with an AMT tweeter. Precise, clean and neutral, with a slight elegant coloration in the lowest and highest registers. Moreover, the Highs here in some places are served by a "spectacular spark", which, like a sparkler, flares up, illuminating the space around itself, and scattering into small specks-stars, sharply fades away, falling into the darkness. Incredible beauty!



Low frequencies are transmitted tightly, accurately and quickly, with good texture and excellent articulation. There is a crisp clap, a tight, biting beat, and a textured nimble bass. It should be borne in mind that the lower case is not very forced, it takes more quality than quantity. The rolls of the drum set blows, like artillery shots, scatter on both sides of the listener, accurately conveying the force of the blow. The density and speed with which the M4 is working out lowercase is simply amazing.

The bass is fast, punchy and extremely naturalistic. It is presented in a lively and temperamental manner in a neutral manner. There is not even a hint of rumble and booming, but there is precision in the reproduction of timbres combined with excellent balance.

The mids are clear, like a mountain stream, neutral and smooth, with excellent texture and excellent resolution. The M4s showcase excellent detail and astounding visualization of sound images in a space with detailed, holographic sound delivery, where no detail escapes the listener.
This is a well-balanced and at the same time emotional performance, where all the elements of the composition are presented with extraordinary precision, large and versatile, with amazing smoothness and informational content. Strings and wind instruments sound clean and distinct, and the vocal parts are transmitted smoothly, naturalistic, very beautifully and moderately expressive. This is a fairly harmonious, spacious and very musical manner of performance.

And here it is simply necessary to return to one of the most important advantages of the M4 - the transfer of the volume of virtual space. Sounds, as if by the wave of a magic wand, as in a three-dimensional image, are scaled and lined up, both in the head and beyond, into a multifaceted harmonious canvas, on which, with the help of sound and imagination, we can build our idea of the spatial form of a sound wave. so to speak, to revive what was heard. And this is just an amazing quality - aerobatics!

High frequencies sound quite clear and intelligible, refined, with good articulation and enviable correctness. This manner of HF processing is a bit like the transfer of this register by an isodynamic or AMT driver. There is a slight accent in the form of a light crumbly spark with a slight brightness.
On the one hand, in this case there are no exquisite after-sounds, on the other hand, it is this manner that gives the overall sound of originality, expression and charm. It is worth noting the fact that with a generally rather comfortable manner, in some poorly mixed and overly bright compositions, such a feature can lead to minor problems and unobtrusive sibilants. Although, in all honesty, I want to say that it still sounds effective, beautiful and comfortable.

In fact, I noticed that this property of the M4 directly depends on the quality of the sound source. If we take a better path and a more powerful amplifier, everything is flawless with the Highs, only the advantages of this frequency range are audible: its peculiar, euphoric manner, which definitely catches me.

By the way, the selection of the sound source also has the most direct impact on the transfer of volume, width and depth of the virtual "sound stage".



In terms of genre preferences, in my opinion, FIR M4s are quite tactful: they play interestingly as classical music, instrumental, jazz, electronics and rock. In principle, things are also pretty good with brutal genres, but it depends more on the quality of the mastering of the compositions. Well, these IEMs play classical music and jazz just great!


M4 - amazing in-ear monitors! FIR Audio mixed in one cauldron exceptional technical competence, impeccable taste and brilliant ideas, and on top they also clearly seasoned it all with a miracle potion. As a result, we have before us “TOTAL IEM” - a model that, in my opinion, deserves the closest attention of all who dream of an exceptional sound.
Such an exquisite audio signature, in my opinion, is able to satisfy the needs of the most demanding music lovers and audiophiles.

You can order the FIR M4, like any model in both (CIEM) and universal (IEM) versions, on the official website for $ 1899.
Yes, the price is not small, but that is how much the sound costs, from which it takes your breath away, and the imagination is turned on to the fullest.

As you probably already understood, I recommend these earphones for purchase without the slightest hesitation.
Thanks my friends 🖐️
A great review, very informative, I would like to get a pair of these IEM'S
If I had to choose one of the four, and even though the M5 is SO good, I'd probably opt for the M4 due to the "cost savings." Such a good sound.


100+ Head-Fier
Pros: Bass, treble, comfort, look, cable
Cons: Detail retrieval, speed, price, vocals are a bit laid back
I had the chance to demo this IEM for about 2 weeks by participating in a loan tour, organized by a member of the community. I would like to thank him for the opportunity !

As a disclaimer, the sources used with the FiR Audio M4 are the iFi Micro Black Label and Sony NW-WM1A. I found the M4 to be fairly resistant to hissing, which makes it quite versatile with sources (big bonus if you're not sure your DAP or DAC/AMP is quiet enough). I also found the comfort to be quite good for long periods, as I did not get any pressure build up whatsoever. Stock cable is quite good. It is pliable, but not the softest. Feels good on the ears, it doesn’t itch or anything.

The music I listen to tends to be quite vast, but it mostly revolves around metal, rock, instrumental and soundtracks. Here is a non-exhaustive list of the bands I used to gather my thoughts : Dream Theater, Haken, Jinjer, Opeth, Tool, Gojira, Killswitch Engage, Lamb of God, Breaking Benjamin, Chevelle, Soen, Karnivool, Andy Timmons, Marco Sfoli, Anup Sastry, Intervals, Plini, Animals as Leaders, Hans Zimmer and Ramin Djawadi. I feel like rock and metal are the best genres for this specific IEM, but the somewhat "relaxed" treble response might not work with everyone.

As far as sound goes, some things sound amazing, some things don’t sound really good. I'm not sure I would say it's a great all-rounder, simply because it does not go well with every genre. Sound signature was fairly pleasant (not harsh) overall, with excellent bass (sub bass is excellent, mid bass is good). Probably one of the better performer in that frequency range. The lower mids have a nice texture and timbre to them. Distorted guitars sounded great ! Vocals are definitely a bit laid back, they sit a bit at the back when compared to everything else in the mix. Not the best detail out there, can lack definition on more complex and complicated tracks. Some instruments just aren’t well reproduced (piano, bass guitar), due to speed mostly. Seems like the drivers can’t keep up. Much better at higher volume, but performance is not that great if you keep the volume fairly low.

Recommended for the price? If you really just want to relax while drinking some whiskey, then sure. The bass response is impressive. But, if you prefer to do some critical listening, then no. A bit on the pricier side of things, would be more competitive at a lower price point (something around 1.3k-1.5k usd), because I would probably take the Solaris or U12t over the M4.
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1000+ Head-Fier
Pros: Sound, extension both low and high, full midrange, craftsmanship, good fit for a universal
Cons: Bass may be strong for some, narrow soundstage (perhaps)

1. Disclaimer: I am not affiliated with FiR. I received the pair of M4 I listened to as part of the FiR tour.

2. Introduction: Abbreviated version: I’ve only had IEMs for a few years. Here I am, looking for an upgrade. My current long-term reference for in-ears is the Campfire Audio Lyra II. I like the overall balance of the Lyra II, but enjoyed the bigger bass of the Vega, though I only got to listen to those for one evening. I have been looking for an upgrade ever since discovering I’m an emerging bass-head.

3. Design: The M4 is a four- way design: dynamic woofer and balanced armature midrange, mid/high and tweeter drivers. I’ve been intrigued by these hybrid designs ever since I bought my Campfire Lyra II. I really like the sound from that single dynamic driver IEM, especially the bass slam (though I now want more depth than the Lyra II can provide). I’ve heard deep rumble from various designs which employ balanced armatures, but those I’ve heard don’t have visceral impact. What I’m hoping to hear from the M4 (as with the M3) is bass physicality from the dynamic driver plus the speed and finesse of the balanced armatures. I hope to hear good cohesiveness in the presentation since only four drivers are used since my current leaning is for fewer drivers.
The housings are generally triangular, and fairly deep. The sound pipes are fairly long. Both of these traits are good for me. Triangular housings seem to fit my ears pretty well and the long sound pipes will let me get deep insertion. I’ve worn ear plugs at work for years, so I am used to jamming things as far in my ear as possible. Shallow insertion feels unstable to me. The housings are nicely made: smooth with rounded edges. They might be die-cast, but I’ll bet they are milled. I don’t see any fasteners holding the face plate to the housing. The outside looks powder coated: satin black for the body, light gold for the face plates. There appear to be vents below the RCX connector (you can see them if you hold your monitor just right).
FiR M3 vents.jpg
OK, you caught me, that’s a photo of the M3, but the M4 vents look the same.

Meze Penta shells.jpg

Lyra shells.jpg The M4 housings are well crafted and understated, like an English luxury car. They are not so sculpted as the Meze Rai Penta I also have (more Italian looking), and cleaner than the Campfire Audio Lyra II.

4. Packaging: I can’t make a comment about the “retail” packaging from FiR as I received my set as part of a tour. Truth be told, I don’t much care about packaging anyway. Sure, it’s nice to see a fancy box, but I’d rather have my money put toward the IEMs themselves; or at least good tips. Honestly, after I put the box in the closet, the next time I’ll see it is if I wrap it up to mail it to the new owner.

5. What’s in the box? What came in the box sent to me was a large (for IEMs) metal can with a screw-top lid containing the M4 a TRRS cable. Also in the box was plastic baggie with some extra tips. The metal can is lined with foam, and has a cleaning brush in the lid. But, it’s too big for daily traveling.
M4 can small.jpg

6. RTFM: No literature came with the tour pair of M4. That’s good, I’d have to spend audition time to read it, anyway.

7. Physicals:

7.1. IEM Connector: FiR Audio use their RCX connector. I won’t quibble about whether it’s mechanically superior to an MMCX. What I do know is I have a few cables with MMCX connectors I can’t use with these IEMs, and I’ve never worn out an MMCX connector. Perhaps musicians do. I hope FiR will offer MMCX as an option for those of us who aren’t hard on their gear. The cable provided came with “RCX angled black” connectors at the IEM end. I didn’t like them at first: they didn’t fit my ears or with my glasses well. I did get used to them, though. Still, if I were to order a pair of IEMs from FIR, I’d try their “RCX Barrel” connector instead. Perhaps a minimalist strain relief and no memory wire that allows the wire to be wrapped over my ear as closely as possible? I’ve also seen some FiR IEMs provided with RCX and clear over-molding that looked smaller than the black connectors…
7.2. Cable: The FiR cable provided with my tour pair is really thin and flexible. It comprises four wires, twisted, not braided. Microphonics weren’t a problem for me. No microphone is offered, which is fine by me.


7.3. Source connector: The tour M4 cable was supplied with a right angle 2.5mm TRRS balanced connector. The 2.5mm plug itself has surprising heft for something so small. The barrel hiding the cable strain relief is surprisingly big. I don’t know yet if it’s actually a big deal, but my initial impression is I wish the barrel was smaller.

20200113_192714.jpg 20200113_192747.jpg

7.4. Tips: I skipped the tips provided with the tour M4. The short version is: I tried Comply 400 foamies, but they created a treble-free zone in my head. I tried JVC Spiral Dots, but they didn’t seal well. I tried the Spin Fit 240 and RHA dual flanges. Initially I didn’t like the Spin Fits and used the RHA for a while, but then changed my mind. I’m glad the tips aren’t borrowed, so I can change them as my whim changes.

M4 inserted.jpg

8. Fit, Comfort, Isolation: I like the shape of the M4 housings. I’ve found, in my limited experience with IEMs, the triangle shaped housings fit my outer ear reliably. I had all kinds of trouble with the Campfire Atlas. Try as I might, I could never get them seated just right, so I hardly ever heard what they are capable of, unless I held them in place. Surprisingly, I had some difficulty with the fit of the left ear piece. It wouldn’t seal reliably with the RHA tips, so I often lost bass response. Holding the ear piece lightly solved the problem for critical listening. I can’t explain that, since the M4 look identical to the M3 on the outside and I had no trouble with the M3. But then I changed back to the Spin Fit and the left stayed in place better. Weird.

9. What I Listened to: I like simple and compact, so I used my AK70 MkII. As far as music, I kept the SD card from my M3 audition, so I listened to the same songs.

10. Soundstage: I am not a soundstaging aficionado, at least not when it comes to head phones. I was surprised by the M4. I had my first, true “out of my head experience”. Listening to the foot steps at the beginning of Chris Rea’s “Auberge”: they started way outside my left ear, crossed the stage and stopped outside my right ear. Also, “Sea Wall” from the Blade Runner 2049 soundtrack filled my entire head with sound. Most other recordings I listened to weren’t quite so dramatic. The like the M3, the M4 soundstage struck me as narrow, it rarely extends past the face plates. They present decent separation across the width of the stage: with orchestral music, violins are on the left, wood winds left of center, brass to the right, celli and basses to the right but in front of the brass The bass drum in Night on Bald Mountain (Mussorgsky, Reiner on RCA Living Stereo) still came from the left. While I don’t notice much differentiation in height or depth, big orchestral pieces sound similar to what I hear from my normal seat at our concert hall: 20th row center. It could be I am not good with spatial cues. I won’t argue with anyone who tells me I’m full of it here. I was surprised to find “Chicago” (Tom Waits, As Bad As Me) to be a mess. Things were more organized through the M3, but still kind of messy through the Trio. Tom Waits’ voice had better separation, but less weight and growl with the Trio (and who wants Tom W. to sound polite?).

11. Highs: Since I have had the M3 in my house already, I was able to listen to the M4 a little more holistically, rather than focusing on the bass first. I’m impressed by the high frequencies of the M4, perhaps more so than the M3 treble. Like the M3, they are smooth and mellow, but there is a bit more energy and sparkle. Plus one for the M4. However; with some of my audition songs, the treble, especially cymbals, sounded tizzy and uncontrolled. I especially noticed when a pair of 64Audio Trio arrived. If the U18t are more detailed than these Trio, I don’t know how U18t fans can stand it. I spent a lot of time comparing the treble of the Trio and the M4. I came to this conclusion: the Trio are sweet. By that I mean extended, airy, light, never sibilant, delicate. The M4 are also extended and retrieve much detail. I can’t call them sweet, though. They are too energetic for that adjective. Thank goodness they aren’t hot.

I liked the added extension and energy of the M4 treble as compared to the M3. That triangle I listened to with the M3 is still pinging away behind the rest of the orchestra in “Siegfried’s Funeral” in Gotterdamerung. Even with the orchestra swelling toward full power, I could still hear the decay of the bell-like tone, at least sometimes. And just like with the M3, the cymbals in the Allman Brothers’ “Jessica” (Brothers and Sisters) sounded splashy and disorganized.

20200113_205050.jpg Transient response is at a high level. I’ll again cite The Doctor by Doc Powell and New Levels New Devils by Polyphia. Sharp attacks and definite stops to each note. Cymbals on The Doctor are much cleaner than on Brother and Sisters, and the M4 also allowed me to hear that with a bit of added oomph compared to the M3. I think the leading edge of the strikes on the cymbals were more distinct, too. All the weird snaps, stops and starts in Polyphia’s “Drown” were there, too. Fun stuff when you’re listening to an articulate transducer.

12. Mids: I spent more time focusing on midrange sound with the M4 than I did when I had the M3. I was pleased to hear more detail in vocals than I remember hearing with the M3. Emmylou Harris’ voice on “Deeper Well” was even more worn and rough than with the M3. That’s a good thing for the character she’s portraying. Emmylou’s voice was also more on the same level with the rest of the music than with the M3. While the M3 bass didn’t mask vocals, with the M4 bass and vocals were more co-equal branches of the music. As far as vocals are concerned, I listened to a few tracks specifically for vocals. Julia Fordham’s voice during “Genius” provides a good contrast to Emmylou: so much smoother than “Deeper Well”. For my first comment about the M4 presentation as a whole I’ll look to “Pusherman” by Curtis Mayfield. Mary Poppins said it best: Practically Perfect in Every Way. Mayfield’s voice is smooth and soulful, the electric bass provides a deep, heavy groove, the bongos are sharp (almost painful when listening loud). Ooh. No, oooh.

I listen to a lot of guitar- based rock and jazz. Jeff Beck, Fleetwood Mac, Boogaloo Joe Jones, Pat Metheny, Wes Montgomery, Rush, Joe Satriani, Steve Vai, and others all made it through the rotation. Actually, I kept my SD card exactly the same for the M4 as for the M3. I loved listening to my favorite guitar players with the M4, too.

Back to the smaller scale tunes I listened to with the M3: while I found string bass in Miles Davis’ “Half Nelson” (Workin’) to be boomy through the M3, it is more controlled with the M4 (cymbals are muted, though). I’ve really enjoyed listening to Henry Brant’s Ice Field. Mr. Brant throws everything at the listener, from organ to triangle. I’ve not heard this piece live, unfortunately, but I think I can hear it all. Rosin on the bows of the bassists? Check. Clinky piano right-hand during the jazzy bit near the end? Check. The celli in Bach’s Brandenberg Concerto 1, were at a non-shocking level, in balance with expectations.

OK, back to mids. For microdynamics and detail retrieval I’d like to hear to nylon-stringed guitar, but I’m not sure I have any in my collection… Pat Metheny provides a good demonstration in “The Sound of Silence” (What It’s All About), steel stringed though his instrument is. As Pat M. plays I can hear the sharp start of each plucked note, resonant decay, but now tremolo in the decay, also. As if the notes are trembling as they rush off. To keep with the parallels of my time with the M3, I listened to “Evolution” by Roy Ayers for that wonderful vibraphone solo. Over the top of a funky bass riff, the vibes dance with quickly struck notes. Sure, the attack is emphasized, but during the slightly sustained notes I can hear the decay of the tubular bells under the keys. One more: the M4 did a good job of recovering details from Keith Jarret’s piano (“Part II C”, The Koln Concert) the M3 left on the table. I could hear the sound board. Imaging was better, too. Keith’s hands ran from ear to ear as he played keys all along his key board. There was distinct separation between left-hand notes and right-hand notes.

13. Lows: There are a couple of characteristics about bass response important to me. The first: Pink Floyd must sound good. One of my favorite things about Dark Side of the Moon, Wish You Were Here, The Wall, et cetera is the bass wraps its arms around you and holds you close. It’s warm and smooth and wonderful. The other is: I would love to find a head phone able to reproduce “It’s For You” by Pat Metheny Group (As Falls Wichita, So Falls Wichita Falls) properly. I am beginning to think this is a fool’s errand, there just isn’t enough volume inside ears to allow Steve Rodby’s bass the room it needs to bloom.

M4 bass is deep and powerful, obviously from the same family as the M3. But here is the only aspect of the contest where the M3 bests the M4: bass impact. Both IEMs shake the foundations of music, but the M3 can make a song implode, while the M4 will merely make it crumble and fall. As during the M3’s stay, “Deeper Well” (Emmylou Harris), “Digging in the Dirt” (Peter Gabriel) and “Dirty” (Earth, Wind and Fire) were my litmus tests. “Deeper Well” failed to make me shiver. The driving thumps in “Dirty” didn’t make my ear drums rattle.
OK, that’s the disappointment. For every door closed, a window is opened, as the saying goes. The lack of startling impact must be weighed against the finesse the M4 brings. Yes, finesse in the bone crushing bass. The synthesized bass notes in “Digging in the Dirt” vibrated rather than simply rumbling. There’s this weird sustained low note in Bob Schneider’s “Ready, Let’s Roll” (King Kong, Volume III), my favorite of all Bob Schneider songs. More King Kong projects please, Mr. Schneider. There’s low-level vibrato that wasn’t as apparent with the M3. At the beginning of “Limelight” (Rush, Moving Pictures), Geddy Lee’s bass is rolling along underneath Neal Peart’s drums. Through most of my head phones, it’s hard to separate the bass from the drums, it’s kind of a muddy jumbled mess. The M4 do an admirable job of sorting that out. As I noted with the M3, added volume helps in sorting things out.

A friend of mine listened for a little while as well. He’s currently a metal-head and prefers his bass leaner and faster than I do. He was not a fan of other well- known bass cannons like the Vega and Atlas. I thought for sure he’d like the Trio better than the M4; he thought the M3 too thick. But, surprise, he liked the M4 low end and didn’t really express a preference, only acknowledged a difference.

Oh, “It’s For You”? Nope, I still need a subwoofer in the living room. But a little less with the M4 (it is a smooth rumbling bass riff, after all).
Before I move on to the next section, let me say a quick word about dynamics. The M4 are. I am, right at this minute, listening to “Take Five” by Dave Brubeck. The snare drum, solidly in my left ear, is painfully sharp. The leading edge of Paul Desmond’s alto notes are sharp and immediate. Both are in stark contrast to that fabulous rolling piano of Mr. Brubeck. A wonderful microcosm of the M4 sound, bolstering what I’ve already touched on when name dropping Polyphia, Pat Metheny and the others.

14. Gestalt, Zeitgeist, Fahrvergnugen (and other German words meaning “the whole enchilada”): Some of this belongs with the conclusions, but here we go anyway. I’ve already noted my disappointment the M4 doesn’t carry the M3’s amazing, addicting bass energy with it. I won’t belabor that point any more. On to some revelations:
  • The M4, like the M3 encouraged me to turn the volume up. I found myself listening at higher volumes than I’m used to. Strangely I wasn’t punished for this with ringing ears or fatigue. The Trios, too. All of them liked power, and rewarded it.
  • The M4 were not relentless like the M3 (or LCD-X). Both the M4 and Trio are better balanced than my memory of the M3, but lacked the undeniable energy the M3 offer.
  • J. Gordon Holt said every song has a “best volume”. That is very apparent with the M4. I found myself constantly turning the volume up and down as songs played. I am left with the impression the M4 frequency response may not be linear with volume? A good example of this is “Red Label” by Danny Gatton (88 Elmira St., genius). Listening at moderate volume bass is recessed and indistinct, as you’d expect. So; however, were the horns. Danny’s guitar, the drums and the cymbals were all up-front for all to hear. Goosing the volume, though, brought out horns (when playing accompaniment, not soloing) and the drums. It is weird that not everything was perceived as louder to me. Another piece I noticed this with was “Lincoln Portrait” by Aaron Copeland. At the same volume I listened to the previous several songs in my audition rotation this piece was piercing and I had to turn it down.
  • The M4 are revealing enough to expose many of my favorite songs for what they are: badly recorded ‘70s and ‘80s rock. Damn them.
15. Comparisons:

64Audio Trio: This time I have a pair of Trio, but am missing the U12t. I’ve already tipped my hand some: the Trio has beautiful treble. The Trio also presents a bit more detail at the top end than do the M4. Skipping the midrange for a moment, the treble difference must be taken at the same time as the bass: here, in my opinion, the M4 wins. The difference is energy level. Even though the M4 doesn’t have the energy of the M3, the Trio doesn’t have the energy of the M4. It’s not like the Trio presents bass as if the musicians are off stage, but they are playing at a lower level than the rest of the band. Detail retrieval is excellent with both contestants, but I had to dig deeper to get it with the Trio than the M4. Back to middle: I’m not going to pick nits: both the M4 and Trio have wonderful midrange.
I’m going to spend a bit more time with the M4 vs. Trio comparison because I spent a whole day’s listening going back and forth. The single-song-litmus-test was a bit of serendipity, it just came up in the mix when I switched SD cards. “Chitlins Con Carne” by Stevie Ray Vaughn (The Sky is Crying) is now one of my favorite audition songs. Bass is deep, full and up in level, Stevie’s guitar tone makes me weep and is nigh isolated in the mids, and the cymbals and rim strikes are made-to-order for treble and transient response. This song single handedly cemented my impression of the differences between the M4 and Trio. When I hear the treble of the Trio I want them and no other. But then I put the M4 back in place and the bass makes me think, “I can live with these highs, and man, this bass digs deep”. There you go.
Meze Rai Penta: What I said about the Rai Penta in comparison with the M3 still stands. They don’t go as low, and lack the force of the M4, let alone the M3. Still a relief for those put off by the Vega, Atlas, or Legend X. Since the M4 are more balanced than the M3, they are easier to groove with, but I’m not sure if they best the Rai Penta in this department. I think that is the prevue of a long-term review. Only when I find myself reaching for one over the other unconsciously at certain times would I know which one is has the more mellow vibe. The Rai Penta’s tweeter is extended and delicate like the Trio’s, but not sweet. It also lacks the razor- sharp transients of the M4. As I said, mellow, grooving. Sitting on the front porch after work and chilling.

Campfire Audio Lyra II: Likewise, what I said about my Lyra II goes when comparing them to the M4 as well. They hold their own quite well in a number of ways with the M4. I still like my Lyra for all the reasons I bought them: bass, smoothness, the cohesiveness of a single driver, a bit of sparkle on top. Oh, and fit. Who wouldn’t love a little bitty IEM that just nestles in like this? They just don’t plumb as deep or soar as high. Small details are missing. The Lyra II simplify the music in comparison to the other IEMs I listened to. The lowest bass is one-notey in comparison. There isn’t quite as much body or expressiveness in Emmylou Harris’ voice, nor Julia Fordham’s. There isn’t as much air around the instruments, as much room sound. Highs are a bit muddier or splashier, less defined. The soundstage is a bit wider, extending out past the cover plates a bit, though not holographic or all-encompassing.
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Here’s how I know the U12t, oops, Trio this time, Penta and Lyra II are all satisfying like the M3 in their own ways: soon after putting any of the four in and plugging them into my DAP, I’d forget about the differences and just listen unless I made a conscious effort to remember I have a review to write.

16. Conclusion: As with the FiR Audio M3, I am impressed with the M4. Sure, the M4 brings a bass rumble rather than the bass power of M3. But in exchange, the M4 brings a more complete portrayal of the sound: nuance the M3 bass doesn’t have, details in the midrange and treble the M3 is missing, and extension and air the M3 lacks. Through it all, they are coherent. Perhaps that’s a good trade. Compared with the Rai Penta, the M4 are harder to groove with, they are more immediate, more insistent. But boy the Rai Penta are soothing. Where I have the most trouble is with the Trio. They are so good at details in the mids and highs I don’t know if I could bear to let that go. Choices, choices. Now where is that lottery ticket?

In the review of the M3 I posted here I said, “Here’s how I know the U12t, Penta and Lyra II are all satisfying like the M3 in their own ways: soon after putting any of the four in and plugging them into my DAP, I’d forget about the differences and just listen unless I made a conscious effort to remember I have a review to write.” That wasn’t the case with the M4: I couldn’t stop listening for the differences between them and the Rai Penta, the Trio and my memory of the M3. I think that may actually be a good thing, since this is a fairly short review period. As I said, I’m looking for an upgrade: a long-game choice (I am not naïve enough to call anything end-game). Which set of strengths can I be happy with? With these, it’s hard to tell. It’s going to take critical listening, dissecting the sound, on and on. It might even take loaners after the tour.

The only thing that bugs me about the M4 is that unreliable fit, and only with the left side. If only FiR offered custom IEMs. Oh, wait.