APEX

64 Audio’s APEX technology is a complex (and surprisingly political) topic behind a rather simple concept: canal pressure relief.

Ignoring all the studies, health benefit claims and the back and forth between Asius and 64 Audio (that I’ll get to another time, all that honestly has no relevance in this breakdown), what APEX does is to essentially provide an outlet for air pass through like an ambient filter. But it’s also not quite an ambient filter, especially for the M20 modules that don’t really affect isolation significantly. It’s really more for the purpose of equalising canal pressure than decreasing isolation.

Each APEX module is filled with an open celled viscoelastic foam (shown in the diagram on the left as #226), which acts as a medium to regulate the air flow between the IEM and the vent located near the top of the module itself. This results in less low-frequency leakage, retaining bass performance whilst achieving the goal of pneumatic pressure relief. The M20 module only has one vent while the M15 module has two (shown as either #229 or #230 depending), which explains why the M20 (named after how it attenuates 20dBs of ambient noise) should isolate more than the M15 (attenuating 15dBs of noise).

The N8’s APEX system actually differs slightly from the rest of the custom models. For the others from the A2e all the way up to the A18t, the APEX module is connected directly to the canal via tubing, as shown below:

The tubing as shown in the diagram as #454 creates a connection between the canal and the outside environment, with the APEX module regulating airflow ideally to the lowest possible amount without compromising bass performance or pressure relief.

Now considering that the N8 already has a bore that connects the canal to the inner cavity for the dynamic driver’s output, there is no longer a need to have a direct connection between the canal to the outside environment via tubing.. All the APEX module of the N8 has to connect to is the inner cavity.

The implications of this is that now the N8’s APEX module acts as a front volume vent for the dynamic driver (well technically it has always been a front volume vent, but now it’s a little more specific) and thus should be extremely sensitive to any changes in the “filter” used. Which is in a way both good and bad; on one hand if you ever want the absolute maximum bass response out of your N8, you’re probably not going to get it out of an APEX module. On the other hand, there are added possibilities for different sounds and signatures due to the higher reactivity to filter changes, especially with (hint hint) third party modules.

The solid core nickel module is a module I purchased from Music Sanctuary and is custom ordered for their own projects. With the N8, it is very clear that it is a system that basically necessitates the need for APEX (or similar pressure relief mechanisms). Inserting the N8 with a solid core module creates a lot of in-canal pressure, especially with a custom fit where one usually gets a vacuum seal. This actually locks the dynamic driver’s diaphragm (which is also referred to “driver flex”, though there is no audible crinkling effect in this case) and bass response is severely affected, at least until I break the seal to equalise the internal pressures or remove and re-insert the solid core module while I’m wearing my customs. The trouble of going through all that just for a little extra isolation or bass isn’t worth it for me.

The other interesting thing is that the APEX connection port of the N8 isn’t fully open, but rather still has an additional resistive filter film/damper attached to it, unlike the universal demo units that I tried prior to my purchase. With the universal demos the APEX connector is fully open, so “going commando” results in complete bass roll-off due to the leakage. On the customs however, using the N8 without any APEX modules is actually a rather viable option, so viable in fact that I actually prefer not using any modules when I’m in a silent environment.