64 Audio supplied me with these modules for my opinion. I want to thank them for their patience as they have been waiting quite a while for my thoughts. Thank you 64 Audio for your great customer service, quality products and patience.

Apex Modules
-MRSP: M15 $99 a set / M20 $99 a set

https://www.64audio.com/store/accessories

I truly love my 64 Audio U12 it is a kick ass IEM. I can tell you it wasn’t love at first listen. It has taken a lot of brain burn-in, cable swapping and trial and error including Apex or Adel. This review is primarily about the Apex module as it is the latest technology utilized by 64 Audio. I wrote a review of the 64 Audio U12(see below) and at that time the review was done with the S1/B1 Adel modules, I didn’t have the Apex at that time. During the review the Adel B1 module was my favorite choice because it opened up the sound a lot more than the S1, which is the one that came with the U12 I purchased. I will say that the M15 Apex has replaced the B1 as my go to module because it opens up the sound that much more than the B1. 64 Audio utilized Adel in collaboration with Asius Technologies and as is the case with many a relationship it ended in divorce so 64 Audio developed their own module…The Apex.

https://www.head-fi.org/f/showcase/64-audio-u12-universal-in-ear-monitor.21832/reviews#review-17865

All of this talk of the S1, B1, M15 and M20 I know it sounds rather confusing, it makes me sound like a Quarterback calling signals behind center. Allow me to simplify it for you and for me as well. We will talk about the M15 and the M20 Apex modules and the effect they have on the sound of my U12. I am not the most scientific guy, you won’t find me discussing the technology behind all of these modules but I will include a link (see below) to the information behind the technology. In a nutshell, it is technology designed to relieve trapped air pressure inside your ears when you are listening to IEM’s. The pressure and vibrations can cause hearing loss, ear fatigue and really screw with US folks that have tinnitus.

http://www.64audio.com/technology

ADEL = Ambrose Diaphonic Ear Lens (B1- S1)

APEX = Air Pressure Exchange (M15 – M20)

If you can notice from the above picture the S1/B1 modules use a tiny hole in the end of the module and the M15/M20 utilize a vent port. The Adel has an internal membrane that kind of represents a second eardrum and the Apex has the vent port. Two different approaches, both designed to relieve the inner ear pressure. I encourage you to do your own search to gather any and all scientific data and knowledge you can regarding Adel and Apex. Again, I stress I am not stating an opinion of the scientific side of either technology I can only tell you my experience with the Apex modules.

My specific tinnitus manifests itself in a low-grade almost constant static that if agitated becomes a louder more annoying static. I am not sure when my tinnitus started but I noticed it, at first, in the still of the night. It was similar to the sound of outdoors late at night where you may hear a slight ambiance as opposed to complete silence. I regularly tolerate a persistent white noise in my ears that I feared would ultimately impede my audiophile hobby. I have learned to concentrate and listen past the static to hear a silent noise floor in a DAP or if hiss exists when connecting an IEM to any given source, anyway, enough about my condition. I will say that I have two different IEM’s that utilize this technology, the 64 Audio U12 and the Zeus XRA. I have become a fan of the Apex/ Adel signature and yes it does give me some relief. It is not a cure but it simply does not aggravate or cause the tinnitus to flare up. I cannot in good faith say that you will have the same results so I would rather stick to the audio benefits of the modules and what you can expect to hear. After all, I consider myself an audiophile or at least someone that enjoys great sounding music.

The sound benefits, shall we?

The sound will ultimately come down to a matter of taste and what strikes your fancy. I will be giving my comparison using the 64 Audio U12. The U12 is a warm, bass powerhouse. I have swapped cables and sources and modules until I found a sound signature that is difficult to match at the TOTL IEM level. My U12 setup of choice is the U12 w/ M15 module and the Ref. 8 cable while using the Opus #2 DAP. It is a SUBLIME setup. It is so different from the U12 I first heard when I opened the box, it has been an incredible transformation.

The apex-m20 module has been made to provide -20dB of noise isolation, the ultimate choice for those seeking the highest level of isolation. The apex-m15 module features a combination of dual ambient ports (that are larger than the single hole in the m20) and modified internals to achieve -15dB isolation.

The M20 is a basshead wet dream. To my ears, it is a really fun and incredible sound. Unfortunately, it is a short-lived experience for me. Paired with the already bassy and warm U12 it is a bass overload to me rendering extended listening sessions difficult. I find it narrows the stage and doesn’t allow the details or clarity shine through. Fun yes, but not my cup of tea. I could see where it would be perfect for the person that is the consummate basshead.

The M15 is the module I use as my daily driver. It has aided in making the U12 the awesome IEM experience I enjoy. The M15 creates an air, a spaciousness if you will and allows the details to shine through with a confidence I didn’t know the U12 possessed. The M15 presents itself with a crispness and bite and I like what it does for the U12.

In closing, there is only so much I can say relative to sound since I am only speaking of a module and not a complete IEM package. Do your research if you are interested in the science involved here. If you are looking for Apex technology and want a bassy signature the M20 will more than satisfy you. If you want more airy openness choose the M15, it truly is a personal decision. I am happy with the fact that there are IEM companies that are trying to deal with the issue of hearing loss, and fatigue. I know my tinnitus and I both appreciate it.