First Look Sunday: FiR Audio M4

FiR Audio M4

In this preview post we check out the FiR Audio M4, a tubeless In Ear Monitor priced at $1,899 US.



Disclaimer: This is a post of our First Look series. A full review of the FiR Audio M4 will come in due course. Here are just short impressions of it.

FiR Audio

I’m quite confident that you’ve run into the name FiR Audio in the last months. FiR introduced themselves into the market with gadgets for the Pro Audio user. First it was IEM vacuum cleaners, then a cable tester and after some more accessory categorized products, they showed the world their take on IEMs.

FiR Audio’s engineers have a long history in the industry. The founder, Bogdan Belonozhko, is the ex-CEO of none other than 64 Audio. A company that is getting bigger and bigger. Bogdan left 64 Audio to follow his own route and was joined by his brother, Alexander. Together they have continuously worked on improving their products and at CanJam 2019 FiR Audio introduced their line-up of tubeless universal and custom IEMs.

Yes, that’s right. Tubeless custom IEMs. We have seen tubeless UIEMs from 64 Audio since the introduction of the Tia Fourté. But a CIEM without tubes and dampers has never been done before. We will check out the custom M5 for you too, but today we’ll quickly take a look at the universal M4.

The FiR Audio M4

The M4 is FiR Audio’s second highest IEM in their line-up, right after the flagship M5. It uses a dynamic driver for lows and three balanced armatures for mids, high mids and highs. The high driver of the M4 sits right at the nozzle, and when you hold the IEM right, you can look at it. FiR’s treble drivers are spout-less, which means the sound does not go through a small spout, but a bigger opening in front of the drivers. It’s not the first time we’ve seen such a driver implemented, as Noble Audio used a similar one for their Savant. Although it was a bass BA driver.

FiR Audio M4

FiR Audio M4

FiR also included their Atom vent system in the M4. Atom stands for Air Transferring Open Module. If you’re wondering, yes, it’s a system in the likes of Adel and Apex. It reduces pneumatic pressure and serves as a secondary eardrum, relieving the user from fatigue. The M4 also features a linear impedance curve, which makes it more resistant to varying output impedance. Its rated nominal impedance is 6.4 ohms.

The M4 is a very well built universal IEM, where face plate and body just seamlessly integrate with each other. When I move my finger from the face plate to the shell, I don’t feel any difference. Overall the M4 is regular sized and I haven’t had any issues with comfort or fit with them. The universal M4 does have one key difference to the custom version. And that’s the use of MMCX connectors instead of FiR’s proprietary RCX connection. The reason behind that is, that the universal is aiming for the audiophile market. A market of people who want to use different cables with their monitors. The RCX connectors on the custom version are a lot more robust, and hence perfect for the professional musician who gives their IEMs a harder time. Personally, I am not a big fan of MMCX as the only sockets that broke down on me where MMCX. A 2-pin never failed me.

FiR Audio M4

FiR Audio M4

First impressions

I started using the M4 with a desktop setup before I moved to a DAP. First time I heard them, they were hooked up to my Chord Hugo2 and XI Audio Broadway S amplifier. What I heard really impressed me. The M4 sounded open, detailed and very natural. The bass is more forward and knows how to punch like Mike Tyson, the mids are organic and full and the treble has good detail and articulation.

I kept listening to the M4 for the entire work-day, and it had quickly won me over. Afterwards I took it with me on a walk to a lake nearby my apartment. And it didn’t sound like before. The Lotoo PAW Gold Touch didn’t quite get it where the Hugo2 and Broadway S pairing went with it. It didn’t sound as open and airy, it still kept its overall warm and full signature, but there was a clear step down in quality to me. Which tells me, that the M4 scales with higher end equipment a lot. Since then I’ve used the M4 in a range of different set-ups, but the most impressive remains the Chord x XI Audio combination.

These are of course just short impressions, and I still have to get a lot more ear-time with the M4. It sure looks like a promising monitor to me. So keep your eyes open for the full review of the FiR Audio M4!

4.8/5 - (17 votes)

A daytime code monkey with a passion for audio and his kids, Linus tends to look at gear with a technical approach, trying to understand why certain things sound the way they do. When there is no music around, Linus goes the extra mile and annoys the hell out of his colleagues with low level beatboxing.


  • Reply May 10, 2020


    Even though the LPGT is a well-engineered DAP, I can’t help wondering if the difference in sound quality might be partly due to the M4 having a crazily low impedance.

    • Reply May 10, 2020


      Hi there,
      thanks for your comment.
      Could be, but it also doesn’t go all the way with my Chord Mojo, which has a very low output impedance. Some IEMs just scale more than others. The M4 is one of those that scales incredibly. 🙂

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