FiR Audio M5 Review

FiR Audio M5

Today we review the FiR Audio M5 custom IEM which is selling for $2799.


Disclaimer: The FiR Audio M5 custom monitor was sent to us free of charge in exchange for this review. FiR audio is not related to Headfonia in any way.


This isn’t the first time we’re looking at FiR Audio, as Linus has already covered their M4 monitor several months ago. As a result you might recognize the chapter on FIR Audio. You can check out his review here:

When I was traveling the US West Coast back in September last year, I happened to be in the neighborhood of the FiR Audio HQ in Portland and I dropped in to say hi and talk about an M5 sample for review. Bogdan and his colleagues were very nice and it was interesting to see how they are doing things in their offices.

Nevertheless, as you can see, it took almost a year to get the sample to me via FiR Audio’s Asian representative. A little warning upfront: this is a very long, multiple page article (mostly because of the many comparisons).

FiR Audio

The company FiR Audio has been in the market since 2018. But their owner and founder has been in the game far longer. Bogdan Belonozhko has been heavily involved with the operations of 64 Audio. Before he left 64 Audio he was their CEO.

In 2018 Bogdan decided to do his own thing and to develop products that fill a niche market in the already niche audiophile segment. He started out building vacuum cleaners for IEMs before he moved on to cables to finally land on IEMs. Which he introduced at 2019’s CanJam Singapore. Here his first creations have been shown to the public.

Unlike the majority of IEMs out there in the wild, his products are completely tube-less. It’s a design that we have already seen with 64 Audio’s Tia Fourté and Tia Trió. However, Bogdan went a step further and announced that his units are also available as tube-less custom IEMs. Something many people, me included, have been requesting from 64 Audio for a long time.

FiR Audio M5

FiR Audio also produces a set of dry cleaners and a cable tester. A complete suite of IEM care and maintenance products to keep your monitors alive and at their best performance. For many weeks FiR Audio also teased a new measurement device to check for faulty drivers. Personally, I’m looking forward to that one myself, but sadly it hasn’t made it past the prototype stage yet.

Aside from IEMs and IEM accessories, FiR Audio also puts very interesting technologies into their own IEMs. Like Atom – Air Transferring Open Module – a module similar to Apex and Adel technologies, where a secondary eardrum is placed within the audio path to prevent the user from listening fatigue. This module helps reduce pneumatic pressure caused by conventional C/IEM designs.

FiR also equips their monitors with a linear impedance curve. This works similar to Custom Art’s FIBAE or 64 Audio’s LID technologies. Usually multi-driver IEMs are prone to partially big impedance swings across the audio spectrum. Here the output impedance of the source can have a massive impact on how a monitor sounds in the end. With a linear impedance curve you can almost guarantee that there won’t be an effect of the output impedance on the signature of the IEM. The sources still have an impact on the sound of the IEM with their own signature, but the output impedance won’t cause for any unusual behavior of the IEM itself. For pro-users this is an important feature, as they often switch production or performance gear with their IEMs. A steady signature across the board is vital for them.

FiR Audio M5



The M5 is FiR Audio’s reference IEM in the lineup and it showcases all of the best tech FiR has to offer.

The M5 monitors features a 10mm dynamic driver for the lows, three BA drivers for the midrange and highs, and one electrostat (EST) driver to assist the treble reproduction.

FiR Audio claims to be the first in the world to implement the electrostatic drivers, in addition to all the other drivers in the M5, in a tubeless design, paired with the 3rd generation atom pressure release system. This to provide the M5 with a cavernous, out of head sound stage and a pressure-free listening experience that is well suited to all professional and audiophile use cases.

These five drivers are set up in a fully tube-less design, which means that each and every driver is performing in its own room in the shell. Room acoustics are a big factor in two channel HiFi, and it has taken very long for IEM manufacturers to adopt this and to make use of that knowledge. Without tubes you don’t have to worry about their own resonances or filters. The driver directly fires into the shell and with that you get more used air space for each driver.

With a nominal impedance of only 6.8 Ohms, the Fir Audio M5 is rather low in resistance. There are no official values for sensitivity. The M5 comes with FiR’s 3 standard Atom modules (grey, black and gold: black 13db, Gray 15db, Gold 17dB).

FiR Audio M5

You can buy the M5 for 2,799$ US directly from FiR Audio’s webshop or through one of their many dealers around the globe. It is available in custom as well as in a universal shape. The M5 comes with a 3 year warranty with the super-reliable RCX connection standard, and unlimited design customization at no extra charge

Package & Accessories

The FiR Audio M5 comes in a very nice qualitative box, which has FiR’s bunny ear logo on the front. Inside the box you first find a document telling you something about the M-series, with on the back a guide on how to insert your custom IEMs.

Under this document you will find a nice foam cut-out with your monitors displayed on top. The cable is hidden under a round FiR Audio sticker. When you lift up this part, you’ll find the FiR warranty card as well as the personalized leather carrying case which holds the 3 Atom sound modules and a cleaning tool.

The M5 comes with FiR’s eight wire SPC cable terminated to a 2.5 mm plug (for my sample anyway). Both the cable and monitor’s feature FiR’s robust version of the RCX connector.

All-in-all the presentation is really nice. The M5 is quite expensive but the box, presentation and accessories are all up to the high-end level.

FiR Audio M5

Build quality, Ergonomics, Customization

Build Quality

The M5’s build quality is excellent and that’s no surprise as the company and the people working there have a lot of experience already with custom monitors.

The faceplate closing is perfect, the RCX connector is very sturdy and the internals neat (though fully packed). The M5 is a rather small monitor and it sports a short nozzle. Inside the nozzle there is a recessed mesh filter but the canals at the end feel soft and rounded, you won’t feel the filter at all.

At the bottom of the face plate you have the Atom modular vent, but it’s all nicely done. It’s also very sturdy and as such I see no issues with multiple module swapping. Just above the RCX connector you can see the vent port for the dynamic driver, but it’s nicely finished.

The only weird thing – but that’s just the way they do things – is the green foam inside the shells. It’s the first monitor in my collection that has it, so it’s quite new to me.

FiR Audio M5

Fit, comfort

The M5 was built based on my reference earmold scans, made by Marcel from Vision Ears. As a result the M5 fits perfectly. The nozzle is short and comfortable but there is a perfect seal. I can wear the M5 for hours without any discomfort at all.


FiR Audio insisted on building the M5 with a smoke shell, so the internals could be inspected and shown in the review. On the inside of the units you have the serial number as well as the first letters of your name and family name.

Originally we were going with a really nice wooden face plate but in the end the M5 sample was built with their special and unique epoxy powder finish. The series is now knows as the Galaxy faceplate collection, and my version is called “Siberian”.

Launching the GalaXy faceplate collection. Siberia, Atlantis and Mars. Available on the designer at #firaudio #galaxycollectoon

Posted by Fir Audio on Thursday, July 23, 2020

On top of the Siberian plates FiR placed their company and M5 logo. It’s a quite nice design and if you want to see more creativities, you can visit their Facebook Page.

You can design your own Fir Audio M5 right here, in FiR’s designer. From what I understand, all customization options are included in the price. This is a very nice extra.

The article continues on page two. You can use the jumps below or click here.

4.3/5 - (91 votes)

Lieven is living in Europe and he's the leader of the gang. He's running Headfonia as a side project next to his full time day job in Digital Marketing & Consultancy. He's a big fan of tube amps and custom inear monitors and has published hundreds of product reviews over the years.

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