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64 Audio U12 IEMs

06-26-2016 | By Smit Patel | Issue 79

Recently, there has been an emergence of innovation and unprecedented technologies which have overhauled the headphone and IEM industry from a stagnant industry to one which is exciting and rapidly ever-changing. Redefining standards within the audio industry is a hard feat to accomplish and so when a company finally does so, it signifies progression; a venture into the next best thing, so to speak.

Enter the 64 Audio U12 - an IEM built over 7 long years of research & design and featuring the revolutionary ADELTM technology. This technology stands for "Ambrose Diaphonic Ear Lens" and comes in the form of a small module which acts as a secondary ear-drum within the ear-canal. The artificial ear-drum touted the ADEL module aims to absorb pneumatic pressures within the ear to relieve the natural ear drums of all the hard work. This not only has the potential to save hearing losses in the future but the module has the added benefit of creating a much wider stereo image amidst a fuller and richer sound. A video of the technology can be seen HERE

The founder of the ADEL technology, Stephen Ambrose, challenged himself in finding a way to preserve human hearing having learnt that personal listening devices could increase the risk of hearing loss by 77%. With a wealth of experience at his disposal, Mr. Ambrose birthed Asius Technologies in an attempt to bring his invention into the marketplace. The company then went onto partner with 64 Audio to create one of the world's best custom and universal in-ear monitors; the U12 and A12 IEMs.

This review shall be focusing on the universal variant of 64 Audio's flagship IEM which sells at a starting price of $1599. The U12 features 12 precision balanced-armature drivers (4 low, 4 mid, and 4 high) in a 3-way cross-over design with 16 Ohm resistance and 117 dB sensitivity. Though the U12 represents a significant investment in the world of personal audio, it is certainly one worth considering owing to its top of the range sound as well as its implementation of ADEL technology.

The Box & Accessories

The packaging of the 64 Audio is quite minimalist with a slide out box depicting stage musician Thomas Miller. The cardboard insert opens up to reveal a hard travel case with all of 64 Audio's accessories inside. These include a cleaning tool, dehumidifier, Comply eartips, shirt-clip, round sticker, and of course the IEMs themselves.

Overall, there is a sufficient amount of accessories to keep an audiophile entertained. However, it would have been good to have included several other silicone eartips alongside their stock double-flange ones to provide even more variety.  


The Design & Build

The housings of the U12 are relatively small for the number of drivers they are packing inside. This helps to aid in the comfort department ahead of Heir Audio's IEM 8.0 and Earsonics' Velvet IEMs. The hard acrylic shell is ergonomically designed and features the ADEL logo on one housing with the 64 Audio logo on the other. The ADEL module slots into the edges of both housings and sticks out only a few millimetres from the base of the earphones. Although not as sophisticated looking as perhaps the Shure SE846, the U12 targets a no-nonsense approach with its matte black design finish.

The cable comes in a detachable 48 inches which in my opinion is the ideal length for any IEM. It features a quadruple-braided design which is durable and tough enough to last for many commutes. Both the Y-split and L-shaped jack of the cable are robust with strong connections and optimal strain relief.

64 Audio U12 IEMs

The Fit & Isolation

As mentioned, the relatively smaller size of the U12 IEMs allows for a more comforting fit. This, along with the hypoallergenic acrylic shell and Comply foam tips make the whole experience closer to one of a custom build. Perhaps an MMCX connector to allow for a fully rotatable memory cable would not have gone amiss to further support comfort levels as is shown by Shure's SE846 IEM. 

Isolation levels are above average with the U12 blocking out ambient noise. However this does decrease with the removal of the ADEL modules as you are essentially forming an open IEM. One way of improving isolation is with the double-flange tips provided.

64 Audio U12 IEMs

Sound impressions

The Bass

The U12, despite being a balanced-armature set, commands strong authority and punch in its bass notes. Sub-bass extension is magnificent with real great rumbling lows and texturing across tracks which demand for it. Compared to the Heir Audio IEM 8.0, the U12 is faster in decay response and impact with the IEM 8.0 having the habit of lingering notes in its rendition of low-end frequencies. The Earsonics Velvet, however, has an even tighter bass than the U12 despite being less authoritative and leaner in note presentation. One thing that the U12's bass excels in is masterfully captivating upon the balance between bass agility and impact. The low-end sounds extremely natural, warm and well-rounded while still being relatively fast, impactful and textured. Perhaps the SE846's bass is the only worthy competitor of the U12's bottom-end. While the U12 wins here on impact and depth, the SE846 presents a more textured and tauter bass line. In tracks such as Beyoncé's "Video Phone", the complexities of the sub-bass are handled skilfully with minimal bleeding into the low-end of the midrange and without perturbing the overall stereo image. The same can be said for James Blake's "Limit To Your Love", where the sub-bass extends very low with detail and hard-hitting presence.       

The Mids

The midrange of the U12 is smooth and organic in tonal character. It is very reminiscent of HiFiMAN's Edition X with this section of the frequency spectrum being ever-so-slightly recessed and laidback. Unlike other IEMs, however, where this type of tonality goes hand in hand with lower detail levels, the U12 manages to retrieve micro-details to make it precise as well as natural sounding. Next to the SE846, the U12 sounds fuller and less taxing than that of the SE846's slightly harsher and leaner midrange. The Heir Audio IEM 8.0, on the other hand, has a much larger vocal presence with an even more analogue sound compared to that of the U12's. Owing to the smooth quality to its midrange, though, there is very little sibilance or glare heard in compressed tracks which makes the U12 an earphone which can be listened to for hours on end. Coming up to the upper midrange, the U12 does lack a bit of energy to give this part of the spectrum attack. This can be dealt with, however, by a few dB increase in the 8-10k mark to provide the needed energy to tracks hovering around this range.

The Treble

Much like the Shure SE846, the highs of 64 Audio's U12 are subdued a bit in line with the rest of the frequency spectrum. This could be a blessing for those sensitive to treble and strident high notes however it could leave those wishing for endless extension wanting for more. In my opinion, the highs tie in with the non-fatiguing and warm signature that this IEM is going for. Despite the tuning of the treble, 64 Audio have tastefully retained the natural timbre of instruments such that they still sound accurate and resolving. The lack of sibilance allows listeners to have extended periods of listening without discomfort and irritation.  

The Matching

The U12 has a sensible rating of 16 Ohm resistance and 117 dB allowing it to be relatively easily driven.    

Schiit Gungnir Multibit & Mjolnir 2 DAC/Amp

With this combination, the U12's stereo image becomes spatially wider with more of a holographic imaging. Bass becomes slightly more impactful and smoother with the midrange delivering even more body and warmth.

Fiio X7 Digital Audio Player

The Fiio X7 paired with the U12 is a delightful combination. The bass becomes tauter with a more balanced sound signature as opposed to that of several tube amps tested. There is very minimal hiss and the more neutral tonality goes very well with 64 Audio's latest flagship.

Fiio M3 Digital Audio Player

Fiio's budget M3 goes surprising well with the U12 as the signature still retains smoothness and warmth while becoming a little bit leaner in nature. Vocals are brought more into the forefront and much like the X7, the sound is tilted towards neutrality.

64 Audio U12 IEMs

The Soundstage & Imaging

Part of the appeal of the ADEL technology has been its impact on soundstage, and the U12 is no exception to this rule. Sonic cues are projected quite wide and deep with good overall height. Obviously this is not enough to compete with some open-back headphones as a few have suggested but the soundstage is certainly above average. The U12 bests the DN-2000J in width, the Shure SE846 in height and the DN-2000 in depth but succumbs to the IEM 8.0 in all of these dimensions.

Imaging is top quality with there being an excellent separation between vocals and instruments within tracks. Despite the smooth and warm tonality, each instrument can be accurately pinpointed owing to the spacious stereo image.


64 Audio have done a good job in capitalising on ADEL's modular technology which has been proven to be more than just a novelty marketing piece. Along with their own input and fine refinement of the U12's tuning, the company has released a force to be reckoned with in the saturated market of personal audio. At $1599, the U12 is by no means cheap but an investment that could certainly pay off in the long run both in terms of hearing preservation and pure sonic enjoyment. What's more is that Asius Technologies are working on the release of adjustable modules to fine tune the listening experience of the U12 to your own liking. Unlike filters which just change the sound of the signature, these adjustable modules feature the same diaphonic lens of the stock ADEL module and have the ability to alter isolation levels. An exciting time indeed—do stay tuned for more…

64 Audio U12

Retail: $1599

64 Audio