64 Audio U8 – unboxing and initial impressions


I have always been fascinated by bass in music. That’s probably why I always feel a little bit of a fraud when someone calls me an “audiophile”, as my tastes quite often encompass a little more lower end substance than the current fashion for a more lean and mean sound. I can appreciate detail and resolution with the best of them, but for me, it doesn’t mean anything without the ability to make me feel the song. As a result, I’ve always had an interest in picking up some 64 Audio gear and seeing if their famously warm and bassy “house sound” ticked my boxes – taking advantage of the recent end of summer sale, I purchased a set of the U8s after a brief exchange with their very helpful customer service team to try and bottom out which would suit me best out of the 4SE, 6 and 8.

Full disclosure – I wasn’t 100% sure what to expect, as I have tried a few of the current 64 Audio lineup (including the Fourte flagship) at the last two London Canjams. Being honest, I was always left a little underwhelmed by the tuning of everything except the Fourte, and even that didn’t blow me back in my seat with awe. This just goes to show that sometimes a first impression can’t give you all the information you need to really assess whether something will work for you sound-wise (especially in noisy show conditions). Fast forward to the last few weeks spent with the U8, and I can definitely “see” what the 64 Audio team are trying to do with their sound and their pressure relieving APEX technology, and why they have such a loyal fanbase. This is the dictionary definition of a sound that grows on you, slowly realigning your preferences as it does. A full review will follow a few weeks down the line, but I have posted a few brief impressions below from my first month with the U8.


For a $1000 set of IEMs, the 64 Audio experience isn’t the most opulent, but there is an elegant simplicity and economy of form to the packaging. The box is adorned with the usual graphics and product picture on the front, and some explanatory text about the company and their proprietary APEX technology on the back. Inside, along with instructions about how to put them in your ears, you find a sealed bag of tips (6 pairs, split half and half between memory foam and silicon), an anti-moisture pellet, one 64 Audio sticker and their 3D printed custom carry case.

The case takes up most of the interior package space, and is probably the best designed example of an IEM case I have come across. Every square inch is crammed with functional space, each IEM shell having its own small compartment to be placed into, with a gap for the attached cables to exit into the main compartment. In the main compartment, a built in cable winder and four “fencepost” style jack holders sit in the middle, allowing you to wind even a thick custom cable like the Effect Audio series tightly and keep everything neat and unbent.

In the lid of the case are the usual wax cleaning tool and shirt clip, both having their own clipped storage space. Overall, it is well thought out, pretty robust and just looks good.

In fact, the only thing that lets down the 64 Audio unboxing experience is the choice of tips – at this price bracket, 6 sets is pretty slim, and the enclosed silicon and foams aren’t actually the best sounding with the U8 – I have found much better synergy with the usual after market options like SpinFit or the foams that came with my Campfire Audio gear. That being said, this is still a very well thought out loadout, the anti-moisture tab showing the “working musician” target audience for the brand.

Initial thoughts on sound

The U8s are touted as the basshead IEM of the original U-series from 64 Audio, and they don’t disappoint down low. With a whopping 50% of the 8 balanced armatures crammed into the shell casings devoted to either sub or mid bass, the U8 can pump out some seriously meaty bottom end. This is still balanced armature bass, however, so it lacks a little in terms of sheer physical impact, but makes up for it with a rich velvety texture, trading slam for substance. The depth of the bass is quite simply superb, producing a highly detailed and thickly layered sound – if there is lower end detail in a track, the U8 will most likely find it. It gives a nice throb to more sub-bass driven genres, and keeps that nicely balanced with the mid bass to avoid the stereotypical “hump” or “thumb” that a lot of monitors go for, preferring to keep a closer balance between the sub and mid bass ranges.

Despite the bass emphasis, 64 Audio market this as an earphone that is uncompromised in the mids and treble, and for once the marketing hype holds true. The mids are smooth and liquid, and not overshadowed by the prominent bass, standing reasonably forward in the mix. The 64 Audio “house sound” is known for its warm tuning and spacious soundstage, and the U8 doesn’t deviate in either of these aspects. Vocals are warm and smooth, sitting a little more forward than neutral, and providing a nice rich undertone to male vocals due to the heavy weight of the bass notes beneath. There is a body and fullness to lower register singing that can be like slipping into a warm bath sometimes, sounding like the aural equivalent of a hot toddy. Fans of a crystal clear or more “reference” midrange can probably turn away now, as while the U8 doesn’t feel particularly coloured in this area, the overall tuning is a little too warm and musical for fans of a true neutral sort of sound.

In terms of detail and resolution, the U8 is no slouch, but definitely not a detail monster. Mid range instruments (guitars, piano etc) all sound clear and nicely defined, the large stage presentation of the U8 allowing each instrument ample room to breathe. Micro-details are present on tracks like “Coco” by Foy Vance, but are not the clearest or most emphasised, showing hints of what the drivers in the U8 are capable of. The emphasis here is far more on tone and substance, giving each note a fully rounded feel and thick presence. Separation is good considering the warm tone of the monitor – this is due mainly to the size of the staging again, with the APEX module tech allowing the U8 to push music successfully outside of the head in all directions, giving a good 3D representation of better recorded tracks in my collection.

One common criticism I hear of the 64 Audio range is the rolled off treble evident in their models. Personally, I find the treble quite nicely done, with a sweet and clear sound to it and decent enough extension for something so warm. It certainly isn’t for those seeking a crystalline and crunchy top end, and despite the huge soundstage it doesn’t exactly scream “air”, but what is there is strong and smooth as silk. It certainly doesn’t feel overly lacking for me, and balances beautifully with the rest of the sound to give the U8 their uniquely warm and solid character.

Source matching

64 Audio started life making IEMs under the 1964Ears brand, aiming their products at the stage musician market. As a result, it has been noted by more than one reviewer that their early gear was tuned with stage equipment in mind. This means much higher output impedance on a portable headphone rig (5+ Ohms, normally considerably more) than you get with a typical “audiophile” DAP.

Why is this important, you may ask? It’s important because it affects the impedance curve of the drivers, which in turn affects how they sound. Playing the U8s through a source with a higher OI like the Shanling M2S, you get a bassy but balanced sound, with good resolution and clarity. Switching to the highly resolving Opus #3 from TheBit (with a figure under 1 Ohm) and the U8 takes on a darker character, the mid bass gaining a little more quantity and the detailing and clarity taking a slight hit in the mid range and upper end due to the additional warmth.

While the U8 is far from unenjoyable with a little more bass (it really does become a true basshead unit), I personally prefer it through something with a higher impedance (like the M2S or some popular fruit-based mobile phones), as it gives a more enjoyably balanced but still warm and smooth sound.

Apex technology

A few years ago, 64 Audio became the first mainstream IEM manufacturer to partner with Asius Technologies, producing the first set of in-ears with ADEL pressure relieving technology. More recently, the design team at 64 decided to take the same basic principle (reduce the pneumatic pressure generated by the IEMs in the ear canal) and launched their own version, called APEX (Air Pressure EXchange). This takes the form of a small cylindrical plug, inserted into a hold in the IEM hell that sits opposite the sound nozzle. There are currently two different modules (the M15 and M20) available from 64, the numbers relating to the amount of sound the filter blocks out, allowing the end user to tweak the sound signature accordingly depending on which filter is in place.

Not being familiar with the effects of the ADEL system I can’t speak to the differences between the two, but as for relieving pressure, the APEX seems to live up to its billing, allowing the U8 to be worn for multiple hours with no listening fatigue or unpleasantness. The APEX technology is also partly responsible for the vast soundstage the U8 is capable of producing, the additional venting creating a more spacious sound in the listener’s ear, almost like an open-backed headphone but with far less loss of isolation. I haven’t had a chance yet to hear the M15 module (the U8 ships with the M20 as standard), but I am very much looking forward to hearing how the other module is able to tweak the sound signature. This also allows the user to tweak the signature slightly by use of the different module, so may offer further tuning variations if 64 Audio decide to bring any more modules on to the market in future.

Final thoughts

As a first foray into the 64 Audio house sound, the U8 has actually impressed me a lot more than I ever thought it would. It packs a warm, bassy punch, with excellent detailing in the lower frequencies and a clear and musical midrange. Treble is slightly dark but not overly so, with a smooth tilt to the sound that makes for a very musical overall sound. These get tagged quite unfairly in my opinion as a “basshead only” IEM, but with the right source, this is a thick and smooth sonic joyride, giving plenty of low end grunt in a very enjoyable L-shaped signature with a great soundstage. Unless you are looking for a lean, mean detail machine, the U8 are a pretty underrated monitor in the mid-to-high end price range in my opinion. I am looking forward to spending some more time with these over the next month or so – full review to follow!

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