Fir Audio Radon 6 (RN6)

Sound Analysis.

I tested and analyzed RN6 sound performance paired up with a neutral LPGT source while playing a variety of test tracks, such as Agnes Obel “The curse”, Sandro Cavazza “So much better” (Avicii remix), C-Bool “Never go away”, Ed Sheeran “Shape of you”, Alan Walker “Darkside”, Galantis “Hunter”, Iggy Azalea “Black widow”, Indila “Boite en argent”, Dua Lipa “Love again”, Counting Crows “Big yellow taxi”, Bob Marley “Jamming”, David Elias “Vision of her”, and Michael Jackson “Dirty Diana”.  I had about 150hrs of burn in time before collected my sound impressions.  Also, I was using stock Symbio eartips and a stock cable.  Below, I will go over the sound description of Universal RN6 with different modules, starting with “black”.


RN6 w/black – W-shaped sound signature with more emphasis on sub-bass. The signature is actually somewhere in between L-shaped and W-shaped, and since the bass is not overwhelming but just more over-emphasized, to my ears it sounds closer to W-shaped tuning with a more natural detailed warmer smoother tonality.  Kinetic Bass DD driver has a deep sub-bass rumble with air vibration you can actually feel.  I mean, it feels like a sub-woofer next to your ears, with more control than in XE6 due to shorter decay of notes and leaner lower mids. Mid-bass is rounded, not too fast or too slow, and has a decent weight, unmistakably DD type of sound performance.  Lower mids are closer to neutral while upper mids have a fuller body and well emphasized (pinna gain) with a natural retrieval of details.  Treble is carefully tuned to give you a natural clarity without any sibilance or extra crunch.  Treble has just enough boost to give the sound its natural clear definition, but it does lack air due to a moderate extension.  You will hear the attack of cymbal crash, but the tail will fade away faster.

The soundstage is relatively wide, oval-shaped, with more width than depth, bringing you closer to the stage while spreading the sound wider left and right.  Layering and separation of the sounds is above average, this is not the analytically tuned micro-detailed iem with “air” between the layers of the sound.  But the sound is not congested like it could get with XE6 in some of the busier tracks.  This is an IEM with a natural rich timbre, elevated rounded bass with a decent control and articulation, organic warmish mids/vocals with good clarity and natural retrieval of details, and a natural detailed treble with a smoother tuning.

RN6 w/red – due to less isolation which should affect the bass, I expected RN6 with this module to have bass with less weight and scaled down impact.  To my surprise, the impact of the bass remained the same as with black module, and sub-bass got even a bit elevated with more textured rumble.  Upper mids sound more open, also being a touch more forward and with a bit more air, and I can even hear vocals spreading a little wider.  The changes I’m hearing in upper mids are probably due to lesser isolation introduced by this module.  The bass change is probably due to more contrast between low end and upper mids, accentuating the bass with more texture and the same level of impact.

RN6 w/silver – I hear bass to be a little more intense with a deeper rumble that adds more weight to the low end.  As a result, upper mids/vocals sound a little warmer and a touch more distant in comparison to red and black modules, making silver module to narrow down the soundstage just a bit.

RN6 w/gold – the bass has a more noticeable lift in sub-bass region and mid-bass impact, scaling both up. Everything else remains the same, but the lift in bass does have the effect on upper mids sounding a bit smoother and as distant as with a silver module.  It feels like with silver and gold the soundstage is a little narrower, while with black it expands, and with red it is noticeably wider.

Personally, I enjoyed red and black modules the most, going back and forth, and at the end decided to settle down on black module.  I do like how red module opens up the mids, gives them extra width and more airiness, but it also creates a bit more contrast with bass.  Black module doesn’t lift the bass as much as silver and gold, which to my ears creates a better balance with mids.  So, I’m leaning a bit more toward black module, but enjoy red one as well.


Eartips Selection.

The selection of eartips is crucial to any universal in-ear monitors and will affect the sound, especially the bass impact depending on the seal.  Due to a large opening of my earcanals, I usually go for the largest size eartips to get a better seal.  Also, please keep in mind, eartips impressions are subjective and will be based on anatomy of your ears.  Here, I’m just describing what I’m hearing with mine (ears) while comparing RN6 stock eartips and other aftermarket alternatives.

w/stock Foam – W-shaped sound sig with elevated bass and more emphasis on sub-bass, natural detailed smoother mids, and clean and clear treble with a moderate extension

w/stock Symbio – similar tuning to stock foamies with a little change in mids having more clarity, a little less warmth, and soundstage gaining a bit more depth.

Azla Crystal – W-shaped sound sig with elevated bass and more emphasis on sub-bass, natural detailed smoother mids that pulled slightly back (in comparison to stock Foamies), and clean and clear treble with a moderate extension.

Symbio F foam – similar to stock foamies and stock Symbio, but I do hear mids being slightly more forward, and also soundstage gaining a bit more depth.  I personally prefer Symbio F since I get a more secure fit with these in comparison to a regular Symbio.  But either one is good.

SpinFit W1 – the sound changed a bit; I hear upper mids being a little brighter and thinner and bass hitting harder.  Not sure I liked this particular pair up, unless you want to raise the bass impact without changing the module.  Actually, it kind of reminded me of switch to red atom module.

Final Type-E – mids became a bit more congested and narrower, also losing some clarity.  To my ears, these eartips didn’t work well with RN6.


Page 3 – Cable pair up and Source Pair up.
Page 4 – Comparison and Conclusion.


7 thoughts on “Fir Audio Radon 6 (RN6)

  1. Hi Alex, I notice you made a comparison with the Ext. Would you say its sound signature is closer to the Phoenix? or maybe even the Phoenix LE?


    1. Dean, if you are referring to RN6 vs Phoenix or Phoenix LE, I would say RN6 mids/treble are closer to Phoenix OG, though RN6 kinetic dd bass slam and texture is the biggest difference, more elevated. BA bass can’t match it. At the same time, Phoenix mids have more clarity and better layering and separation of the instruments because its “BA” bass has a better separation from mids.


  2. how much time of burn in did you use for this IEM?
    my unit is more neutral and bright than your description
    I use “not your father’s” cable and N8ll, P6pro and SP3000


    1. If anything, burn in will only make bass settle in, to clean up a bit of a bloat out of the box. What you are describing sounds like you might want to play with different eartips to make sure iem sits tight and secure in your earcanal. If you are breaking the seal or it’s not secure, kinetic bass will be leaking more sound causing them to be more neutral and brighter.


      1. Maybe…i’ll try more eartips when my burn in period is over, but it’s a very good IEM indeed, only need a bit of finetuning for my tastes.
        I loved the Kr5, but i sold it in favor of this one, i needed a more technical version of the Kr5…but for now this is another thing, more balanced and with a tighter bass…


    1. ciao man, just replied to you on head-fi 😉 “Mids get warmer and soundstage is narrower, giving the sound a more intimate feeling with a smoother tonality. With or without atom xs module, it’s just another finetuning option.”


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