Fir Audio Radon 6 (RN6)


The sound comparison was done using RN6 with a stock cable, stock Symbio eartips, black atom module and LPGT source; volume matched in every comparison.

RN6 vs XE6 – due to more clarity in mids, the perception of RN6 soundstage expansion is wider, including more accurate imaging of the sound placement.  RN6 also has more control and better articulation of bass due to shorter decay of notes without spilling into lower mids.  RN6 also has more sub-bass rumble.  In contrast, XE6 bass notes are more rounded, more relaxed, with a sound being more laidback.  While upper mids and treble here are very close, the lower mids are noticeably different with XE6 being thicker and fuller, while RN6 being leaner, closer to neutral level.  As a result, mids/vocals have a very noticeable contrast where RN6 has a lot more clarity and resolution, while XE6 has a lot more body and laidback musicality.  To my ears, the tuning is different and complementary in nature.  If you want tighter bass with more clarity and higher resolution in mids, RN6 is the way to go.

vs XE6 CIEM – one of the differences I found between XE6 uni and ciem, relative to my ear anatomy, was ciem having more clarity in mids due to a better fit.  XE6 uni has a bit more heft, and due to its extra weight combined with an open grill design of kinetic DD driver, the seal was looser.  XE6 ciem improved that, but RN6 takes it to the next level due to the updated tuning and lighter shells which result in better fit, for my ears.  When comparing XE6 custom to RN6, they are closer in tuning then XE6 uni vs RN6.  The biggest difference is still in mids where RN6 lower mids are more neutral which gives bass a better control and opens uppers mids with more clarity and higher resolution.  Also, deeper insertion of customs usually producers a wider soundstage perception to my ears.

RN6 vs KR5 – in comparison, the soundstage expansion between these two is not too far off.  KR5 sounds a bit wider due to its more revealing mid-forward tuning, but RN6 is not too far off.  RN6 bass goes deeper and hits harder, while KR5 bass quantity is scaled down.  It has a similar quality, being tighter, faster, and more articulate, but the quantity of KR5 bass is noticeably less.  As a result, KR5 mids are more forward than RN6, but they both have a natural detailed tonality, just a little more coloring in RN6.  Treble tonality, extension, and resolution is very similar between these two.  As a result, I find RN6 to be in between of XE6 and KR5, having more powerful impact and deeper low end extension like XE6 and more clarity and higher resolution of upper frequencies like KR5.


RN6 vs Empire LX – as soon as you start talking about any IEM with a noticeable bass impact, LX always comes up in a conversation.  Bass quality between these IEMs is not too far off, just scaled down a little in RN6, enough to keep LX in L-shaped tuning bracket and bring RN6 down to W-shaped with “extra bass emphasis”.  The mids of LX is somewhere between XE6 and RN6, having more body than RN6, but not being as thick as XE6.  Both have upper mids with natural detailed tonality.  Treble is also very close, clear and natural without any exaggerated peaks and a rather moderate extension.  Leaner nature of RN6 mids also contributes to a slightly wider perception of the soundstage in RN6.

RN6 vs Vision Ears EXT – right away a noticed a different soundstage expansion where RN6 is more oval shaped, spreading wider left/right while EXT is narrower in width but has more depth, bringing vocals further out of your head.  EXT bass slams harder, more elevated, also sounds a little faster, while RN6 bass has a deeper sub-bass, more laidback mid-bass, fuller body and smoother mids, and also smoother treble.  The difference in mids gives EXT a more revealing and slightly colder tonality while RN6 sounds smoother, warmer, laidback, and more relaxed.


RN6 vs UM Mentor Multiverse – I had someone asking me about RN6 vs MM comparison, figure to give it a listen.  MM is tuned with a more expanded soundstage and more holographic imaging.  RN6 soundstage is wide, but doesn’t have the same depth to give it a holographic feeling.  Also, MM mids are leaner and a little more revealing toward the upper side.  But the biggest difference here is in bass which is very different.  The powerful slam/extension of RN6 Kinetic DD driver feels more physical while Mentor bass is more relaxed and softer and more polite and accurate in comparison.

RN6 vs Aroma Jewel – these two have a similar soundstage expansion, but the rest is completely different.  This example was also by request, something I wouldn’t even consider using in comparison with RN6.  Despite having DD bass, the weight and the impact of Jewel’s bass is noticeably scaled down.  Jewel bass has a nice texture, but it’s nowhere near the RN6 bass level.  Mids are leaner and more revealing in Jewel, while RN6 has smoother, warmer, fuller body sound.  Overall, Jewel is noticeably leaner and less colored in comparison to bassier fuller body sound of RN6.  If anything, you get both due to their complementary tuning which is quite different.



In the conclusion of my original Frontier Series review, I talked about how manufacturers are trying to stand out from the crowd in today’s competitive market, trying to differentiate themselves, even attempting to reinvent the wheel which is not an easy task.  Fir Audio gave it a shot and they did come up with something quite original because I still don’t recall seeing any other similar open back bass driver design along with replaceable venting modules, tubeless drivers, etc.  And after a year of using XE6 and now RN6, in my opinion, it is not a visual eye candy or a marketing gimmick because it actually works as advertised where you both hear and feel the bass.

So, is RN6 a retuned version of either XE6 or KR5 or a new design?   That’s the first question I was asked after I started sharing my impressions.  And once people realized that RN6 has the same driver config as XE6, I was also asked if switching atom modules, especially to red, can bring XE6 tuning closer to RN6 or the other way around with RN6 and gold module.  To my ears, RN6 sounds like a retuned version of XE6 and no module or eartips change alone can bring these iems to the same level.  Lower mids retuning in RN6 made a world of difference to my ears, bringing more clarity and resolution to mids and more control and better articulation to bass.  As result, the tuning between RN6 and XE6 is noticeably different and quite complementary rather than one being the improvement of the other.

I still find XE6 to have the warmest tonality with the bigger bass impact and thicker fuller body analog sound tuning.  KR5 is the most revealing with a faster bass, more detailed and less colored mids, and crisper treble.  NE4 takes from both of these IEMs, with a bass that is not as elevated as XE6, but still having a stronger mid-bass impact, not as thick lower mids, and smoother and less extended treble which results in a less resolving organic tonality.  RN6 takes the best of all 3 under the umbrella of one all-rounder tuning that has a powerful bass impact which is still under control without spilling into mids, more detailed yet still naturally colored mids, and well-defined smooth treble response.  As usual, opinions are subjective, but to my ears RN6 hit the sweet spot at a cheaper price than XE6.


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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