64 Audio Adel U6

A worthy sidekick to a true flagship!

PROS: resolving, detailed, natural sound, ADEL module, slim design, accessories (the case!!!), great pair up with many sources.

CONS: additional cost of MAM/S1/B1 modules, not for those craving revealing/analytical sound, benefits from cable upgrade (subjective).

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

Manufacturer website: 64 Audio, some models available for Sale on Amazon.



It’s never easy to work on a review of another in-ear monitor model after doing in depth coverage of the flagship from the same manufacturer.  I was very impressed with a sound tuning and ADEL technology behind 64 Audio U12/A12 flagship which I covered in my other review, but afterwards received a number of questions asking how it compares to one of their mid-tier models featuring half of the driver count.  The price/performance ratio topic always gets a lot of attention, and I’m starting to notice that more people, who previously got caught up in a tangled web of driver number wars, are now taking a step back to re-evaluate their priorities.

You also have to be realistic about the law of diminishing returns, but in case of the latest 64 Audio A-/U-series models, regardless of the number of drivers or the price or the custom vs universal fit, they all feature innovative ADEL technology that acts as a secondary eardrum to absorb the harmful pneumatic pressure and to reassure a safer listening while avoiding the risk of hearing damage.  Since I already covered about 64 Audio and Asius Technology (creators of ADEL) in my original U12/A12 review, please use it as a reference for addition info.  The intent of this review is to focus on their 6-driver U6 model, and to go into more details about its performance, comparison, and pair up.

As a spoiler, I want to say ahead of my write up that if you are expecting a conclusion with “Don’t waste your money on U12 because U6 is almost as good” – it’s not going to happen because no matter how you look at it, the U12 is still a flagship in its full glory.  But U6 sounds great as well, and got one important trick up its sleeve where some might even consider it instead (or maybe in addition to) of U12.  Want to find out more?  Then, let’s move on to the review!

Unboxing and Accessories.

Even so I wasn’t planning to cover the info already mentioned in my original U12/A12 review since the packaging is identical, I can’t help myself but to gush over it again.  Regardless of the model or the paid price, everybody is treated like VIP with a compact packaging box that has just enough room for a 64 Audio custom travel/organize case, portable dehumidifier container (goes inside of the case), and 64 Audio sticker.  If you are receiving Universal series version, you will also get a pair of Comply foam eartips in S/M/L sizes and a pair of medium double-flange silicone tips.

The cover of the packaging sleeve features a company logo with a picture of monitors corresponding to either Universal or Custom fit design.  When you slide a sleeve off, you will see a flap with a picture of a performer and “Hear Everything” underneath – what to expect when using 64 Audio monitors.  Where it gets more interesting, once you lift the cover flap up you will find a Quick Start Guide with a lot of great pointers about headphone listening safety, volume advisory and proper way to put in-ear monitors in your ears.  Right from the start you get a sense of 64 Audio and Asius Tech really caring about your ear health, one of the main benefits behind the featured ADEL module.

I did mention that everybody is treated like VIP, but don’t expect champagne and caviar – instead you will get one cool custom case.  Everything from a wide easy to handle latch to an air valve eliminating build-up of inner case pressure when you close it, from an individual earpiece storage areas with removable rubber lining to a custom built-in cable winder, and including a place to plug right angled headphone jack and to place a round dehumidifier container, as well as a cover with a built in organize to hold securely a shirt clip (included), a cleaning tool (included), and up to 2 sets of ADEL modules – everything is custom tailored and well thought of.  There is even enough room for a thicker replacement cable, though a straight jack will not fit into right angled storage pocket so keep it along with a cable.

When you placing the order, you can also specify to etch your name on top of the storage box to personalize it.  While everybody uses an off the shelf Pelican or Otterbox storage cases with a pre-cut foam insert, 64 Audio went one step ahead with their own custom designed case which protects your headphone investment and keeps everything organized inside of it.






All 64 Audio IEMs/CIEMs feature a replaceable cable with a standard universal 2pin connector, reassuring you can use different after market cables to customize the appearance and to upgrade the sound.

If I’m not mistaken, the bundled stock cable was actually updated and now features a more durable design.  The cable utilizes a regular OFC wires in a tight soft black rubbery jacket, with 4 separate twisted conductors keeping L/R ground connection separate going into the right angled gold plated headphone jack with a nice rubbery housing and a decent strain relief.  The y-splitter is just a piece of a shrink wrapped tube and chin slider is a clear short piece of the tube as well.  This chin slider has a good friction and doesn’t feel loose.

Next to the 2pin connector you have a piece of flexible memory wire in a soft shrink wrapped tube, and the connector itself has a red/blue dot to indicate Right/Left designation.  With a pre-shaped memory wire, there is no worry about mixing the polarity of 2pin connectors between earpieces since it has the same orientation, but when dealing with replacement cables – polarity of the connector has to be consistent, both pins facing the same way especially when you don’t have a memory wire.  Also keep in mind, universal series models only have a surface mount socket because there is not enough room for a recessed one.

The stock wire does its job and seems to be built ok.  But in case of U6 with replacement cables the sound change was noticeable enough for me to switch and never look back.  As my usual disclaimer, not everybody believes or hears the audio benefit of replacement cables.  I’m not trying to convince anybody, but rather sharing with you my personal experience.

U6 has a very impressive sound tuning, but with a stock cable and even some silver plated (SPC) replacement cables I felt that performance was held back, especially when it comes to mids.  I went back’n’forth numerous times, listening from different sources, even at different times of the day just to make sure my mind is not playing tricks on me, and I consistently came to the same conclusion that a stock cable makes mids sound flat and a bit dull.  But once I replaced the cable with pure silver wires – not only did bass become more articulate and tighter, but also mids came to life with more sparkle and better dynamics.

I actually hear the improvement in audio performance not only with pure silver, using Whiplash latest TWag v3 T (Teflon) series, but also with pure copper (TWcu) cable where it added a little more texture to the low end.  Trying it with Litz SPC (Linum) or regular SPC (Noble cables) had a more subtle effect, but not as noticeable as with other two cables.  Just keep in mind, as much as I enjoyed the sound improvement with TWcu – it’s 8-conductor braided cable where you are dealing with extra weight and reduced cable flexibility.  With TWag v3 T-series, the silver wires are thinner and more flexible, and it’s not an issue that Whiplash doubled the number of conductors to 8.  But be prepared to deal with some serious microphonics effect, especially amplified by ADEL module due to reduced isolation.  I’m actually found that TWag v3 T-series sounded better than TWag v3 and TWau when paired with U6, but I had to use an electric tape wrapped around R/L sides of the cable between the memory wire and the wooden chin slider.  That reduced microphonics significantly since the cable was no longer rubbing against my chin.

Cable replacement is not a must have upgrade, and I don’t expect everybody to hear the same level of improvement as I have.  But for me personally, after trying U6 with different cables and settling on the one with pure silver conductors – I didn’t want to go back to a stock cable.

Whiplash (TWcu and TWag v3 T-series).



My U12/A12 review covered Custom IEM experience where I used 64 Audio on-line Designer to customize A12 and then enjoyed on-line tracker which keeps you up to date with every single step of the design/manufacturing process as you wait for CIEM.  With Universal IEM the ordering process is a lot simpler since everything is already preconfigured and you don’t need to customize anything.  It’s not exactly an instant gratification since you still have to wait a few weeks, but typically the wait time is based on the current queue of orders rather than delays associated with a custom model build.

All Universal series models have a similar design shape and use hypoallergenic hard acrylic material.  They all have a non-transparent solid piano black finish with “ADEL” printed on the right earpiece and “64 Audio” emblem on the left earpiece.  The faceplate is flat, and the overall shape kind of reminds me of a guitar pick with one trimmed side.  While the faceplate side of the shell has a more defined edge, inner side of the shell is more rounded and smoother.  The nozzle is quite extended and at 8mm probably the longest among my other IEMs, but that reassures a deeper insertion and a more secure fit, at least for my ears.  Also, the nozzle has a slightly thicker part in the middle where 64 Audio etches a number corresponding to a driver count, plus this thicker part helps in keeping eartips from sliding off.

The nozzle has a quad bore symmetric design where 3 of the bore openings go to sound tubes connected to corresponding clusters of 2-low, 2-mid, and 2-high balanced armature drivers, and the 4th bore opening goes to ADEL module cavity which is aligned opposite of the nozzle on the faceplate.  Even so nozzle is extended, it feels pretty sturdy.  Obviously, the internal design of each shell has 6 balanced armature drivers partitioned in 3 groups of 2, and also an integrated 3-way passive crossover.  The impedance of 22 ohms reassures compatibility with many different sources, but sensitivity of 115dB means that some low level of hissing to be expected with more powerful sources.

Though the thickness of universal series shell is relatively slim, it still sticks out a bit out of my ear meaning no luck with falling asleep while wearing these.  Another thing to keep in mind, even so all universal series models have the same exterior shape and finish, U12 is thicker in comparison to accommodate twice as many drivers, but we are only talking about a few extra millimeter of thickness.



U12 vs U6.


The fit.

Page 2: ADEL modules, Sound analysis, Comparison, and Conclusion.

One thought on “64 Audio Adel U6

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