Portable Rock Concert: Fir Radon 6 Review

Video Review:

What can Radon 6 do that others can’t? Today we will look at what is so special about this TOTL from Fir Audio.

Specs

• 6 Driver IEM, 5 way crossover 
  • 1 DD
  • 4 BA
  • 1 Est 

• Impedance: 28 ohms
• Frequency Response: 20Hz – 20kHz
• Connection: 0.78mm 2 Pin (non recessed)

Rating

• Tonality: 9.5/10
• Technicality: 9.5/10
• Enjoyment: 9/10
• Build: 4.5/5
• Comfort: 4.5/5
• Total: 37/40

Note:
This IEM is purchased for myself directly from JABENSG. I did try it multiple times before purchasing.

Introduction:

Fir Audio has been in the market for about 6 years. The Radon 6 was designed to be a limited edition of 300 sets utilizing technologies from their different line ups as a way to celebrate their 5th year anniversary. The IEM, unlike the rest in the market at this point, do not have a ridiculous amount of drivers with large shells, and instead have a complex 5 way but with only 6 drives. The question is what did it deliver that made me buy it and why should you consider it.

Build Quality

The Radon 6 build quality is good. Made out of metal, it feels solid and built to last. The IEM is on the smaller side, very similar to Audio64 style IEM but just a little thicker. The two pins are the non recessed style so you have access to a wide variety of cables. Fir claims their “Rigid” build for the 2 pin connector is both durable and replaceable. The Radon 6 comes with Symbio W and Foam Tips. I personally didn’t like either for Radon 6 which I will go more in depth later before the sound sections. The cable is a silver cable with a balance connector. It is of pretty good quality, doesn’t get tangled easily and not too tough to bend around. I do not have any negative things to say about the Radon 6 built quality.

Comfort:

Radon 6 is a comfortable IEM to wear. The small build and relatively long nozzle allows good insertion into the ear with just a little protruding out. It is possible to lie on the bed with these IEMs though directly lying on the ear piece itself is likely not very comfortable on the long run.  

Sound Quality

Tracks Used

• Backlight by ADO
• Backlight Replica by Vaundy
• Yuusha by Yoasobi
• Ibara by ADO
• Eien no Akuruhi by ADO
• Inside You by Milet
• The Witch from Mercury by Takashi Ohmama
• One Winged Angel by  Nobou Uematsu

Equipment Used

• Shanling M9+
• AK SE300
• Enleum HPA 23 RM
• Mass Kobo 475

Compared with

• A64 U12T
• FatFreq Maestro SE
• UM  Multiverse Mentor
• FatFreq Scarlet Mini

ATOM Modules:

For this review, I will use mainly the ATOM Silver Module (Neutral). The module will change the soundstage, bass and isolation. 

In general, red is the least seal, most open and the least bass, followed by black, silver and gold. I do think the bass difference is not so much of the elevation, but the increased isolation that makes the lower frequency more prominent. The silver to me is my preferred balance, with good bass, good isolation and still maintaining a good soundstage size. The black is the alternative for me if I want a slightly more open sound with trade off to bass and power. 

Kinetic Bass & Tips:

Due to the kinetic bass design, where there is an open vent in the Radon 6, placing the IEM as close and as deep in the ear produces a more impactful bass. Just note that most of the bass is still about your seal as the tip is where the sound comes out from into your ears. The exterior firing gives a nice kick to the impact which is the biggest reason I got this IEM. Just note, sound will leak from the IEM through the kinetic bass port, you may not be able to hear others but others standing close enough can hear you!

Tonality

Overall Tonality is W Shaped. With Bass, Vocals and Highs emphasis. The sound is on the neutral warm side, warmer than U12T. A very balanced sound that is easy to hear and appreciate, with all the energy but not the vocals sounding far behind.

Soundstage

Mid – Large Size Soundstage depending on which ATOM module you use. On the silver module, its more of a slightly bigger than midsize stage, where most of the music is at the edge or slightly outside the head. If you compare, it sits between the U12T (Mid) and the Maestro SE (Large). Tracks like backlight fills the entire width of the head and a little more. Listening to Eien no Akuruhi extends the vocal and its “Air” beyond the years slightly. Layering is pretty good, similar to most good IEM. The only IEM with a better layering from memory is the Onyx, which has a distinct front back depth when it comes to instruments. 

Clarity and Separation

The Radon 6 excels in this, with only the Maestro SE being comparable for clarity and separation. Listening to the Backlight Replica, you can hear the softest electric guitar easily. In tracks like the Witch from Mercury, there is clear separation between all the instruments, allowing one to appreciate the various percussion instruments that can go really subtle in the mix while still getting the grand vocals and mid instruments playing. 

Energy

Over time I notice different IEM have different energy levels in their rendition, which is a combination of multiple factors. The Radon has the energy and speed of the U12T, making it an exciting listen in most ADO songs. This is likely attributed to the forward powerful mids of the Radon.

Bass

This is where Radon 6 is special. There are many IEM with good bass, FatFreq Maestro SE is one such example. But most bass are a trade off, between impact and extension into the sub bass where most of it is feeling rather sound. Fir Audio utilises Kinetic Bass, which is an exposed bass driver that vents the energy into the ear in addition to producing sound into the canal. It operates on a very similar thought process of a Bone Conductor, but rather than vibrate, it ejects the pressure onto your ear to give you the effect of the “feel of the bass”. What this translates into is even though the exact listened amount of bass may not be huge and rumbles your canal, the venting pressure onto the ear produces the feeling of impact and deep bass texture. This works when you use tips that are small and snug, so that the IEM is as close to your ear as possible. The outcome is a bass that has a lot of perceived impact, rumble and texture, making it sound very similar to a headphone style bass. To prove a point, I compared it to the Scarlet Mini which has 30 DB of Bass elevation. The Radon 6 actually sounds rather close in most situations unless it is some song with really low bass tones, that’s when you hear more bass in the Scarlet but the amount of feeling you get and the texture is still similar to the Radon 6 which also has way more punch. To sum up, the bass on the Radon 6 is phenomenal, the best I ever heard on any known IEM in the year of 2024. 

Mids

Mids on the Radon 6 is powerful and forward sounding. It is clear and well separated, never sounding confusing unless at really really high volume. Vocals are relatively full bodied and smooth, though the U12T and Multiverse Mentor have a more body to the sound with the Mentor having a really smooth mids. That said works male vocals really well, with the Vaundy voice in Backlight being superbly rendered with power and relatively forward. For female vocals, I do feel they can at times sound slightly further.  I did notice when listening to Yuusha, Ikura’s voice may seem a little more distant but clarity and air in the voice is still very well retained. It does make songs like Eien no Akuruhi feel super smoother. Instruments that sit in the mids however are well rendered, especially picked guitars, which the pick attack sounds really precise on the Radon 6.

Treble

Treble has the sort of energy, clarity and extension that is quite unique. Now its not as much as what I remember of the annihilator, but it’s definitely ahead of the Maestro SE in terms of quantity. I do think that the Radon 6 sits on the fine line of going overboard for some tracks, but it makes cymbal crashes sound really high in energy with the extension and decay being top notch. The only issue is for me, it can get a little too sparkly at times, which I will have to lower the volume a little. Swapping between this and the U12T makes the U12T sound dull. This extended treble does make string instruments also sound really good. 

Overall:

To me the sound signature is right up my alley. High clarity with a balanced signature that has a good amount of soundstage and one of the most engaging bass without the bloom and roundness associated with high bass elevation. 

Source and Amplification

Radon 6 is easy to drive , however it does benefit from good amplifications. In general it tightens the bass and opens the sound stage slightly while giving better clarity. The difference is slight but going from cheap wireless hooks like BT20pro to high end DAP output such as Shanling M9, the difference is pretty apparent. However the amps do not change the characteristics of the Radon 6. 

Shanling M9+ built in amp: This gives a little more depth to the bass but rounds it slightly. Mids have a touch more body. If you prefer a smooth and wide experience, this is the preferred configuration. 

M9+ with Mass kobo 475: Gives a more punchy bass, a wide sound with slightly more distinct separation. If you prefer more clarity with dynamics, this is better. 

Comparison

A64 U12T

I find the Radon high in energy compared to the U12T. It however does feel a touch less dynamic. The Radon is also overall a smoother listening experience with little harshness in most tracks, allowing for longer listening durations for people who are sensitive to mid high to treble energy. 

FatFreq Maestro SE

Radon 6 has a smaller soundstage, a fully mids and a bass thats punchy with good rumble but doesn’t have as much “bass sound” as the Maestro SE. I also find Maestro SE more airy and smooth, great for songs that are meant to be more soothing like Eien no Akuruhi. Radon does render the music with more energy and punch, which can be really exciting for Rock style songs like backlight. 

Conclusion

The Radon 6 to me is a really good IEM. However in today’s IEM world, good is no longer enough. The Radon 6 niche is its first class bass, the very best between quantity, punch and texture. It may not have the most bass or extended treble, however the energy it conveys is top notch throughout the spectrum. If you are looking for a IEM to rock your time away, the Fir Radon 6 is a great choice.