Snapshot: FIR Audio ATOM XL modules


PROS: cost effective fine-tuning of your 64 Audio and FIR Audio IEMs, customizes the look of the faceplate.

CONS: not always easy to remove the module (depending on a socket of IEM model).

The product was provided to me free of charge for the review purpose in exchange for my honest opinion.

Manufacturer website: FIR Audio.  Priced at $149 for a set of 3 pairs.


As I already covered in my review of FIR Audio pre-production m5 IEM, their new line of monitors introduced ATOM module (Air Transferring Open Module) which is basically a controlled leak valve intended to relief the air pressure.  While the ATOM used in FIR Audio IEMs is smaller in size, they also made XL version to be compatible with Apex modules, allowing them to be used with 64 Audio IEMs.

The following is going to be a brief review, part of my new Snapshot Series with shorter write-ups and the focus on the design and the sound analysis.  Not gonna spend too much time on other aspects, though I have to say that packaging presentation was unique.  A small custom wooden round case with a company name/logo on the cover, description of each colorful module pair on the back, and sockets to secure modules inside.

With the cover off, it almost looks like one of those wooden peg games.  Btw, these are not as easy to remove from the case, and I had to use a chip extractor (the one you can get for a couple of dollars off eBay) which also comes in handy when removing modules from IEMs.  I do completely understand, keeping them secure inside will prevent modules from flying out once you remove the top.  Just be careful and pull these out with a twist when removing it.



As already mentioned, ATOM name is an acronym for Air Transferring Open Module, allowing front venting of the drivers directly into the shell.  Basically, it’s a controlled leak valve intended to relief the air pressure which results in non-fatigue open sound listening even at higher volume.  Many will probably recognize ATOM XL to be similar in functionality to Apex module, but they do differ in the method of how this leak is created and controlled.  I don’t know enough design details to explain the difference, but I can confirm that I was able to raise the volume beyond my normal listening level and experienced neither sound fatigue nor ear pressure discomfort with IEMs I tested.


The module uses a precise medical grade machined tubing and comes in 3 colors (anodized) to distinguish each pair.  It also supposed to be resistant to shock, if you drop it.  The colors correspond to gray (N, neutral baseline), black (-, reduced bass), and golden (+, increased bass).  The baseline N has 15dB isolation and correlates to M15 Apex module.  The (-) has lower 13dB isolation which yields a reduced bass, while the (+) has higher 17dB isolation which helps to lift the bass.


Sound Analysis.

Each pair of the modules were tested on 64 Audio U18t IEM and 64 Audio N8 CIEM, using LPGT as my source, and making sure everything is volume matched.


First, I started by comparing N module to Apex M15 (gunmetal) and Apex M20 (silver).  With both U18t and N8, I was able to confirm that N module sounds very similar to M15, just with a touch more sub-bass rumble using N.  Switching to M20 resulted in a more noticeable sound change.  When comparing N vs M20, I found M20 to have a little less airiness, soundstage being not as wide/deep, and M20 having a beefier low end with a little more sub-bass and stronger mid-bass.


Next, using the same U18t and N8, I compared all three ATOM XL pairs.  With N module being my baseline and having characteristics closer to M15, when going to (-) I heard a reduced sub-bass, making the bass a little leaner which gave mids/vocals more focus.  Going to (+) module extended and lifted sub-bass, enhancing the bottom end without exaggerating it too much.  Seems that going between + and – pairs had a bigger effect on the sub-bass without changing mids/treble.



Similar to Apex M15 and M20 modules, the intent of ATOM XL is to give you another set of tools to fine-tune the sound of your IEMs.  And we are not talking about changing the sound signature or having a more drastic effect like an EQ.  Depending on the original signature of IEM, now you can fine-tune the low end response to your liking.  We all have a personal sound preference.  For example, with N8 I preferred a black ATOM XL (-) which gave vocals more focus and made bass a little more balanced.  And with U18t, I preferred a golden ATOM XL (+) which gave the bass more weight.

2 thoughts on “Snapshot: FIR Audio ATOM XL modules

  1. I know you use the U18t a lot. For fun, non-review listening, what module do you like the best out of the 64 and Fir options?


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