FIR Audio Krypton 5 Review

FIR Audio Krypton 5

In this article we review the FIR Audio Krypton 5 (Kr5) IEM, it’s selling for $2,999 USD.


FIR Audio kindly supplied the Krypton 5 for this article. We’re not affiliated to FIR Audio in any way.

FIR Audio

For those that have never heard of the brand FIR Audio, here’s a little introduction. This custom and universal IEM company has a lot of background packed into their short brand-history. Started by Bogdan Belonozkho, former CEO of 64 Audio, FIR has quickly risen to one of the most innovative and sought after brands in the scene.

FIR Audio is the only company – to my knowledge – that produces tube-less custom In Ear Monitors. 64 Audio has been working with tube-less universals, but have never released one of their models as a custom shaped build.

That, however, is not the only thing that makes FIR Audio unique in the field. They also just introduced a new version of bone conduction – called Kinetic Bass. It’s actually a rather simple thought that turned out very well. They just point a dynamic driver right at the concha of your ear, rather than having it fire into it. Thus making you perceive bass vibrations basically coming from the outside. Similar to a speaker performance, but limited to your ears, rather than your whole body. This can also be seen as a sort of bone conduction, where sound vibrations are picked up by your bones and directed to your eardrums. It’s a cool effect and once you get used to it, you develop a kind of crave for it.

FIR Audio’s line-up of products spans from In Ear Monitors (custom and universal) to maintenance gear and other accessories. I have one of their IEM Vac cleaners and think it’s an excellent investment to take care of your monitors. You can find all of our FIR Audio reviews here.

FIR Audio Krypton 5

Kr5 (Krypton 5)

The Krypton 5 is a tube-less, hybrid In Ear Monitor, that uses a dynamic and a Balanced Armature driver for lows. Yes, both of them. A pair of BA’s takes care of the mids, while another BA replicates treble.

What’s interesting about these BA’s is that they are open drivers. Meaning they don’t have a spout out of which the sound comes out of, but have their “doors” open. Those drivers radiate directly into a specially constructed chamber (which FIR calls their Sound Reactor). The mids and dynamic drivers are directly connected to the Sound Reactor, while the treble driver radiates onto a Sound Reflector. Which basically is a surface designed to reflect the sound straight into your ear canals. If you have ever seen 64 Audio’s implementation of the tia drivers, you might have spotted, that it’s directly FIRing into the walls of the nozzle. FIR directs the sound waves at an angle into your canals.

On a tech-spec level the Kr5 has a frequency range of 20Hz-20kHz with a rated impedance of 22 Ohms. I couldn’t find any ratings for sensitivity, but from what I could tell, these are relatively easy to drive, though scale with higher power.

FIR Audio Krypton 5


The package itself is very nice and sturdy. It comes in a compact box that houses your IEMs, an iron-on patch, a warranty card and a leather case. In this case you will find four sets of silicone tips, one of which is double-flanged, one pair of foam tips, two additional ATOM modules (black and gold) as well as a small T2 screwdriver and a cleaning tool. One pair of silicone tips is already installed on the Kr5, making a total of six tips.

I am really digging the leather case and have been using the one from my custom Xe6 ever since I got it.

Build Quality

The build quality of my Kr5 is just excellent. The shells are made silver anodized aluminum with sapphire glass face plates. Underneath the sapphire glass there’s a carbon fibre pattern and the Kr5 as well as the FIR logo in silver. The units themselves are a lot smaller than they seem on pictures. Before I had them in hand, I thought these would be satellites hovering next to my ears, but that’s far from the truth. These are even small enough to fit my girlfriend’s ears. However, the body is a bit bigger than what you might be used to. Especially if you know FIR’s M-series of IEMs, these are noticeably smaller in height than the Kr5.

The Kr5 comes with what FIR calls their rigid 2-pin connector. Any regular 0.78mm 2-pin cable will fit the Kr5, FIR managed to make the connectors themselves more reliable, withstanding thousands of inserts and removals of cables.

The ATOM XS modules are found right below the 2-pin connectors, and with the supplied T2 screwdriver you can change these modules and alter isolation values as well as bass response. The silver (pre-installed) module offers isolation of 15db while the gold adds 2db to isolation and to 20Hz bass response. The black module will give you the lowest levels of isolation (13db) and lowers 20Hz bass by 2db.

The review continues on Page two!

4.1/5 - (131 votes)

Been into music and sound since he was a little brat, but spent his profession in a more binary field making things do what they were supposed to do. Ultimately just another dude on the internet with an opinion, into which you shouldn't put too much thought.

1 Comment

  • Reply February 14, 2023

    Kevin F

    Curious about what ‘waterfall’ means in terms of the Hugo2.

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