There is now a custom version of the Model E12, which I tested some time ago in the universal version, with a special feature that I came across after my Bellos X4 review. It is the design of the nozzle itself. In normal custom IEMs, these tend to be longer and ultimately sit very deep in the ear canal. This is different with the Bellos IEMs and also with the E12 Custom. This unique FlexFit Canals technology from Fir Audio uses a shorter nozzle that does not sit so deep in the ear canal. This is achieved by an attached silicone ring that adapts to the shape of the ear canal and thus ensures an even and comfortable seal. Matching silicone tips, as with Bellos IN-AIR-CANAL Technology, are not necessary with the E12 Custom.
After sending my ear impressions as STL files, it only took 6 weeks until I held my E12 Custom in my hands. For an extra charge, you can also reduce the production time to 3-7 days. Having already had very good experiences with my other two custom IEMs (Bellos X4 and CraftEars Omnium), I have to say that the E12 Custom also fits my ears like a glove. But before I go into the comfort and sound, a few things about the technologies used in the E12.
Instead of many different drivers and complex crossover networks, the Fir Audio E12 uses just one dynamic driver that covers the entire frequency range. For the first time with the E12 model, Fir Audio introduces SwapX technology, which makes it possible to replace the faceplates quickly and easily. Using magnets on the faceplates and an included tool that works like a suction cup, the faceplates can be changed in seconds. There is a designer on the Fir Audio website that allows you to order ready-made faceplates in various designs or upload your own image files.
Fir Audio has also improved the durability and maintainability of the E12. The entire shell can be removed with screws under the faceplate. The 2-pin connectors, which are also used in the Frontier Series, are very stable and designed for up to 1000 mating cycles. Even if the connectors break after many insertions, they can be easily replaced with a set screw. If you want even more stability, you can choose the RCX connector for the E12 Custom, which is even specified for up to 5000 mating operations! I opted for 2-pin, as all my after-market cables are also designed as 2-pin.
The E12 uses Tactile Bass Technology, where the entire cabinet is coupled to the dynamic driver and acts as a secondary transducer, resulting in a more intense bass. One advantage of this technology is that, unlike Kinetic Bass technology, no sound escapes to the outside. As a result, the E12 provides better isolation from the outside.
In addition, the E12 is equipped with the ATOM Venting System, which ensures more relaxed listening through pressure relief, reduces listening fatigue, enlarges the soundstage and enables a more natural sound reproduction. While the ATOM module is permanently installed in the E12 Universal, the E12 Custom has interchangeable ATOM modules. The fixed module in the E12 Universal corresponds approximately to the gold ATOM module and offers the strongest bass range with maximum isolation. The silver ATOM module corresponds to the standard tuning of the E12 Custom and has slightly less bass (-2dB) than the gold module. The black module in turn has slightly less bass (-2dB) than the silver module. This means that only the E12 Custom allows you to tune the sound through the modules. These modules are already available on the Frontier Series, but previously an additional tool was always needed to change them and the modules are really tiny, so this always means a bit of fiddling around. Not so with the E12 Custom. They are slightly larger here and can be pulled out with the help of fingernails and then simply pushed back in. This makes it as easy as with the APEX modules from 64 Audio.
As with the E12 Universal, the build quality of the E12 Custom is once again typically Fir superb. Instead of a metal housing, a non-slip and very scratch-resistant material is used here. This ensures that the E12 Custom always sits comfortably and firmly in the ear canal. The comfort is really top notch and you don't have to worry about the E12 Custom slipping or coming loose during sudden movements. The seal is also maintained during normal chewing movements, just like with the Bellos X4. For all those who have problems with the longer nozzles on custom IEMs, the FlexFit Canals technology could be the solution. After some time with the E12 Custom, you no longer notice that you are wearing an IEM in your ear. I only know this from the Bellos X4. I can always feel my Omnium, which sits much deeper in the ear canal. For me personally, however, this is not unpleasant as it is not a pressing feeling. But I know that some people can't cope with a "normal" custom IEM.
For the E12 Custom, I opted for faceplates in a dark design and also for a Hardshell Plus, which incidentally costs no extra. This Hardshell Plus has enough space for all the accessories as well as the E12 Custom and cable. I find these round leather cases simply too small. The scope of delivery includes the Fir patch, a letter from CEO Bogdan Belonozhko, a cleaning brush, a suction cup for the faceplates, replacement silicone rings and two additional pairs of ATOM modules. The cable in 4.4mm termination is the same as the E12 Universal and Radon6. An 8-strand pure silver cable with a copper shield. As I already wrote in my E12 Universal review, this cable is really good in terms of sound quality and in the price range up to 1799 USD certainly one of the best that is supplied with IEMs.
For the sound test this time I not only use my iBasso DX320 MAX Ti, but also my FiiO M15s and the iBasso PB5 korg tube based amplifier that I use together with the DX320 MAX Ti. With an impedance of 16 ohms, the E12 Custom is very easy to drive and I find myself almost exclusively in the first gain stage of all the devices I use.
In terms of tuning, the E12 doesn't have much in common with a specific Frontier Series model. Tonally, it fits somewhere between them. On the one hand, it produces a brilliantly strong bass range with its 12 mm dynamic driver, which plays quantitatively at XE-6 level with the golden module, while the treble is boosted more and the mids don't sound quite as full as with the XE-6. Overall, the Custom E12 sounds a little smoother to me than the Universal, which is even more energetic in the treble than the E12 Custom with the golden module. With the golden ATOM module, the E12 Custom sounds slightly warm tonally with a V-shape tuning with a very strong bass range. However, if you then gradually go down with the modules, i.e. silver and black modules, the audibility, airiness and separation improve. For me, the E12 Custom actually sounds most balanced with the silver ATOM module. But even with the black ATOM module, the E12 Custom still has sufficient reserves in the bass range and the treble never becomes unpleasant or sharp. I can imagine that many would even prefer the E12 Custom with the black module. Here it works very coherently with a tuning that most reflects the technical finesse of the E12 in terms of resolution, bass quality and separation. As I said, my personal favorite is the silver module. I reach for the gold module when I want to listen to EDM or hip hop and punch and slam are most important to me.
When I use the golden module, the combination of M15s and E12 Custom plays best for me. The slightly brighter basic tuning of the FiiO M15s is advantageous here compared to the more earthy basic tone of the DX320 Max Ti. However, when I use one of the other two modules, the DX320 MAX Ti + E12 Custom clearly plays in a higher league. The more natural reproduction, bass quality and stage presentation clearly trumps the M15s. Coupling the PB5 to the DX320 MAX Ti results in an even more gripping sound image, but then it loses some of the very wide soundstage. That's why the silver module in direct operation with the DX320 MAX Ti is clearly my favorite!
The greater comfort and the possibility of sound tuning with the ATOM modules makes the E12 Custom my first choice over the Universal model, especially as the price is identical for both models. With the FlexFit Canals technology, Fir Audio has something in its portfolio that no other manufacturer offers with the exception of Bellos Audio, which was also created by the Bellos brothers. So it's no coincidence. At the moment, only the E12 Custom is officially equipped with FlexFit Canals technology. But I'm sure this will change in the future and this technology may also be offered as an option for the Frontier Series.
While the E12 Universal with its fixed ATOM module will make every bass lover happy and is certainly a first choice for modern genres such as EDM, hip hop, metal and rock, the tuning options of the E12 Custom make it easy and quick to adapt the repertoire to other tastes with a level of comfort that is unparalleled in the IEM sector anyway.
