FiR Audio Frontier Series (XE6, KR5, NE4) Introduction and Comparison.


Frontier Series introduces three models, each with a unique name and a number corresponding to total drivers.  Xenon 6 (XE6, $3,899) uses 6 drivers: 10mm kinetic DD bass, 1x open BA bass, 2x open BA mids, 1x open BA high w/sound reflector, 1x EST ultra high, and has 28ohm impedance.  Krypton 5 (KR5, $2,999) uses 5 drivers: 10mm kinetic DD bass, 1x open BA bass, 2x open BA mids, 1x open BA high w/sound reflector, and has 22ohm impedance.  Neon 4 (NE4, $2,299) uses 4 drivers: 10mm kinetic DD bass, 1x open BA bass, 1x open BA mids, 1x open BA high w/sound reflector, and has 22ohm impedance.

Regardless of a driver config, the exterior dimensions of these IEMs are the same, only varying in the shell material/finish and faceplate design.  Top of the line XE6 features a machined stainless-steel shell (14g each) with gold plating exterior and sapphire glass faceplate over carbon fiber with infused gold flakes.  The next one, KR5, has an aluminum shell (8g) with a shiny chrome-like plating and a sapphire glass faceplate over carbon fiber with a granite-like pattern.  NE4 also has aluminum shell (6g) with a similar chrome looking plating, sapphire glass faceplate, and unique granite-looking faceplate pattern.  Obviously, SS shell will be the heaviest, and the difference in weight between KR5 and NE4 is probably due to additional BA driver.  Each universal pair has infamous “bunny ears” artwork on the right side and either XE6, KR5, or NE4 logo on the left side.


But one thing will remain common between all Universal and Custom Frontier series models, the main feature of the design, the Kinetic bass.  It refers to 10mm Dynamic Driver that is open and ported under a mesh cover while facing outside through the back of the shell.  By design, it offers a hybrid conduction system, allowing you to hear the low frequencies in two ways.  One is through air-conduction of the sound hitting your eardrums via the nozzle, and the other one is by means of bone-conduction from the back of the driver transmitting directly to the ear cartilage through the bones in your head, converting to kinetic energy as it reaches the inner ear (cochlea).  That is what this Kinetic Bass is about, a hybrid conduction where you can both hear and feel the bass.

One thing I did notice, while the driver size is the same, the actual Kinetic driver opening of XE6 is bigger than KR5/NE4, which probably explains XE6 having a more elevated bass impact relative to KR5/NE4.


Also, every IEM will have Atom (air transferring open module) pressure relief system which reduces ear fatigue during extended listening and at higher volume by venting pressures that build up in a sealed ear canal.  As it was already mentioned, UIEMs use small screw-size Atom XS modules, while CIEMs with removable module option use a regular size Atom X.  XS does require a tool to remove it.  Not going to deny it, it’s a finicky process where you have to be very careful not loose XS module, thus make sure to use a well-lit area and a flat surface.  Furthermore, as you screw the module in, there is no hard stop, it will continue turning once inside, which is OK and expected.  Per FiR Audio, “The thread on the module is only to help back the module out when removing, there is no thread in the receiving pipe.  You can simply press the module in on insertion gently until it stops, no spinning required.  This feature uses what we call a soft thread.  It can’t strip so no worries on that.”

Frontier Series IEMs come with a set of 3 Atom XS/X pairs:

  • + Isolation 16dB: gold
  • N Isolation 15dB: silver
  • – Isolation 14dB: black

Frontier Series also features FiR Audio Open Acoustic system which is part of the tubeless driver design.  The low and mid BA drivers are open with no sound tubes, radiating directly into the sound chamber, referred to as Sound Reactor which uses natural acoustics instead of dampeners and filters for the shaping of the sound before it reaches your ear canal.  The high BA driver, also open, is located inside the nozzle (canal stem) and uses a Sound Reflector instead of Reactor, to direct high frequencies into the ear canal.  Basically, everything is tubeless and all sounds get mixed together naturally while directed to your earcanal.

Another unique feature of Frontier Series is Rigid Technology which improves the reliability and durability of the design, and even allows you to “service” IEM thanks to its modular components which you can replace yourself instead of sending it back to manufacturer.  The universal 2pin shell socket is part of this rigid modular design which you can replace if you ever run into a problem.  Also, you will find a snap screen at the tip of the nozzle which can be replaced by removing a spring ring that holds it securely in place.  And when it comes to CIEMs, the 3D printed shells are 20% thicker than average for a better protection of the internal components.

The fit.

For the reference, relative to FiR Audio M-series and 64 Audio IEMs, the faceplate size/profile is smaller, but shells itself are deeper.

Frontier series universal shells do sit comfortably inside my ears, but they also stick out a little more.

Page 3 – Sound analysis and Conclusion.

4 thoughts on “FiR Audio Frontier Series (XE6, KR5, NE4) Introduction and Comparison.

  1. Out of these 3 FiR Audio IEMs, which one do you prefer? To me, it would be the KR5 w/ Silver Atom XS because it seems to be the least colored IEM.


    1. Quite a few people mentioned to me that since they want less colored, more transparent tuning, KR5 would be the way to go, as an upgrade to M5. I prefer XE6 because it offers something different to complement the rest of the IEMs I have and use daily, but some might find it on a warmer and a smoother side of their preference.

      Liked by 1 person

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