FIR Audio M5


PROS: neutral natural resolving tonality, strong bass impact, tubeless hybrid design (DD/3BA/ESTAT), ATOM module (internal or removable), RCX connector (2pin optional), 3yr warranty.

CONS: price, bass impact controlled by tip rolling.

The product was provided to me free of charge for the review purpose in exchange for my honest opinion.

Manufacturer website: FIR Audio.  Available for sale directly from FIR Audio or Music Sanctuary.


Making its debut at CanJam SGP ’19, FIR Audio unveiled a brand-new addition to their product line, custom IEMs in various multi-driver (balanced armature, dynamic, and electrostatic) configurations:

  • M2 – hybrid DD/BA: DD low-mid, BA hi-mid ($799)
  • M3 – hybrid DD/2BA: DD low, BA hi-mid, BA high ($1,199)
  • M4 – hybrid DD/3BA: DD low, BA mid, BA hi-mid, BA high ($1,899)
  • M5 – hybrid DD/3BA/ESTAT: DD low, BA mid, BA hi-mid, BA high, ESTAT-high ($2,799)

When I reviewed their headphone VAC last year and then had a chance to test their custom cables, I didn’t realize those audio accessories and other tools introduced under FIR Audio brand were just teasers while Bogdan Belonozhko (CEO, founder) and his team were cooking something bigger in their lab.  And for those who are not yet familiar with FIR Audio, I’m sure many will recognize “Belonozhko” family name and their very driven band of brothers who have been involved in designing and manufacturing of IEMs for the last decade under 1964 Ears turned later into 64 Audio.

FIR Audio was founded last year (2018) by Bogdan as a separate company, and the name comes from Fir Trees, a type of evergreens common to Pacific Northwest region of Washington state, not a coincidence since the company is located in Vancouver, WA.  If you look closer at their logo, the “I” in FIR is shaped like a fir tree, though there is also a logo of rabbit eating a corn on their headphone VACs which I believe has its own story behind it.  But regardless of the name, the logo, or the legacy, the focus of this review is on FIR Audio brand new flagship M5 hybrid IEM I had a chance to test over the last few weeks.  So, let’s find out more!

Unboxing and Accessories.

M5 arrived inside of an aluminum round jar with a twist off lid and a replaceable dehumidifier container attached to it.  The jar has a removable soft foam lining to protect IEMs during shipping, while the dehumidifier pellets container is intended to remove the moisture from IEMs.  It’s not exactly a pocket friendly travel case, but quite functional for luggage storage while traveling and using it as a portable dehumidifier.  The top of the jar lid had FIR Audio logo/label and my “Twister6” name which could be customized in a Designer when placing the order.

The provided accessories include a set of foam marshmallow eartips, a cleaning tool, and a small leather strap with a snap-on button to organize the cable.  Keep in mind, this is a universal 3D printed demo of their Custom IEM, thus a reason why eartips were included.  Obviously, don’t expect to see it with your CIEMs.

Another optional accessory I received was RCX to 2pin adapters.  It will certainly come in handy if you order FIR Audio monitors with RCX connector and would like to use it with your 2pin cables.  The pigtail adaptor was long enough to comfortably fit over my ear.  Just remember that many aftermarket cables have a pre-shaped flexible earhook, so it won’t attach straight, unless your cable has a memory wire or no earhook.

Later, FIR Audio sent me a new version of their ultra-short angled RCX adapter which is more compact.  If you have a large collection of 2pin aftermarket cables, both of these adapters will be quite useful.


While I didn’t have to go through FIR Audio IEM designer when I received my M5 demo unit, this tool now incorporates their Custom Cable designer found on FIR Audio cables page.  In there you will be able to select from a variety of 13 different termination plugs, 4 different wires (in 2 color jackets), customize the wire length, pick slider/splitter color (black or white), and select RCX connector.  2pin is available upon request when you contact FIR Audio directly, or you can order a separate adapter for your 2pin cable.

My review unit arrived with 8-conductor matte black SPC (scorpion wire) cable, terminated with 4.4mm BAL plug, black custom y-split and a matching chin-slider.  At the IEM connector side, no memory wire was used, only a flexible pre-shaped shrinkwrap going to the housing of angled RCX connector with R/L marking.  The wires are very supple, with a soft rubbery black jacket, inner twisted in 4-conductor bunches for Left/Right sides going above y-split, and each bunch twisted again going down to the gold-plated 4.4mm balanced plug with aluminum housing and carbon fiber insert.  Overall, the cable felt very strong and durable, and non-microphonic.

I’m sure many will be curious what is this RCX connector all about.  It’s a new type of IEM connector which kind of reminds me of mmcx since you are not dealing with two separate pins and don’t have to worry about the polarity.  But at the same time, it’s different from mmcx, especially since the base of the connector is squared, interlocking when mated to prevent rotation.  The mating parts of the connector seem to be durable and feel secure when snapped together, and according to FIR Audio those are rated up to 5000 insertions.  In theory, you will get less wear and less room for dirt to get inside.

2pin connectors are still dominating IEM industry and they are considered to be more reliable than mmcx since the cable doesn’t rotate, causing to lose contact or to get specks of dirt inside.  But 2pins and their sockets could have tolerance issues when dealing with aftermarket cables, can loosen up after a while, and you have to pay attention to polarity.  RCX, like mmcx, just snaps in without worrying about pin polarity and its square locking design prevents it from rotation.

Just my personal opinion, but I think audiophiles who enjoy cable-rolling and already invested into many 2pin premium cables will probably go for 2pin connector option.  Or maybe they will try RCX to 2pin adapters.  It’s hard to change audio industry “standards” overnight, but I do want to give FIR Audio credit, at least for trying, and I think musicians who want a more reliable cable connection will appreciate this change from the get-go.  Otherwise, only time will tell.

Aftermarket cables.

Having RCX to 2pin adapters allowed me to try a few different cables, just to compare the effect of cable rolling with M5.  Here is an example of what I found using the latest Effect Audio Vogue series while comparing it to FIR Audio Scorpion cable.

  • EA Maestro (copper) cable – very similar tonality, just a touch more sub-bass rumble.
  • EA Virtuoso (SPC) cable – nearly identical, I don’t hear much difference in tonality.
  • EA Grandioso (copper/silver hybrid) cable – also a similar tonality, just a little more sub-bass rumble and a touch more sparkle in treble.

In this comparison, cables didn’t offer too much of a change in sound, instead I found more drastic changes when switching between different eartips which I’m going to describe in Sound Analysis section of the review.


Page 2 – Design.
Page 3 – Sound analysis.
Page 4 – Comparison, Pair up, and Conclusion.

One thought on “FIR Audio M5

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