Premium metal shells, MX and M20 apex modules included, Powerful and dynamic bass, Superb organic midrange tonality, Ultra-clean tia driven highs, Easy to drive with linear impedance design
Separation leaves to be desired at times, Could do with more top-octave sparkle
If you enjoy a gorgeous, organic tonality and don’t mind a slightly laid-back midrange, the U6t is an auditory delight and a fully formed high-end IEM experience.
We’ve all heard of 64Audio; their models are some of the most coveted on the market and their flagships especially, are considered some of the best in the world. However, fewer have had the privilege of owning these models that are priced to match their top-level performance. In this sense, I’ve always had a soft spot for their lower-end IEMs that I think are sorely slept on and more rarely discussed in the audiophile community. Perhaps you could even say 64 themselves played a part in this problem as their cheaper universal earphones have never seemed to be as high a priority as their high-end ones. The new tia touting universal line-up turns this mindset on its head. Not only has the technology of their flagships been brought down to their more accessible models, but all aspects of the experience have been enriched to match. The original U6 remains a personal favourite as a warm, coherent earphone with a rich voicing. The U6t is a total refinement, taking very clear inspiration from the U12t’s signature and filtering it down to a significantly more attainable price point – you can see why this has become 64 Audio’s best-selling model. After seeing my colleague’s review of the custom A6t, I was ecstatic to try the new universal variant for myself.
The U6t retails for $1299 USD. You can read all about their range of IEMs and technologies, and treat yourself to a unit of your own on 64 Audio.
I would like to thank Logan and Charlie from 64 Audio very much for their quick communication and for accommodating this review of the U6t. All words are my own and there is no monetary incentive for a positive review. The U6t was provided on a loan basis and is to be returned to 64 Audio following review.
- Drivers: 6x Precision Balanced Armatures
- Configuration: 1x tia high, 1x high-mid, 2x mid, 2x low
- Frequency Response: 10 Hz – 20 kHz
- Sensitivity: 108 dB
- Impedance: 10 Ohms
- Crossover: Integrated 4-way passive
Behind the Design –
tia driver + single bore
You’ve seen tubeless balanced armature drivers and anyone who has heard a good implementation will tell you there are indeed benefits to this approach. 64 Audio take this one step further with tia, considered by many to be an industry-leading innovation in BA tech, by removing the entire roof of the driver. The company reason this provides a lower resonance delivery of sound whilst optimising transient response. The driver is then placed within the single-bore nozzle that 64 posits to act as a sound shaping path. Furthermore, the short sound path to the ear enables them to deliver a more linear and coherent frequency response. Combined with the unique driver, you get an extended, high resolution image. This definitely isn’t just a marketing ploy as anyone who has experienced tia IEMs in person will agree the proof is in the pudding.
There are many challenges when designing in-ear monitors, one that is becoming increasingly spoken about is pressure relief. Increased wearing pressure is an especially large issue with in-ears as they form the tightest seal with the ear canal. This can alter the perception of sound over time via the tympanic reflex (causing tension on the eardrum) that results in decreased sound transmission to the inner ear – effectively reducing the perception of dynamics, bass and treble, and resulting in a much less resolving sound. Standing for air pressure exchange, apex is a similar style of technology as ADEL and ATOM. It alleviates pressure on the ear canal via pneumatic venting controlled by the size of the aperture and the composition of the viscoelastic foam inside. 64 Audio carry 4 modules, MX (-10dB), M15 (-15dB), M20 (-20dB) and the closed M26 module intended for the company’s custom earplugs. These permit varying levels of openness and sound tuning. Sonically, the company state that apex aids soundstage and bass perception.
Another challenge of IEMs is that the popular and efficient BA transducer has a limited bandwidth, so multiple drivers are often utilised to deliver a full-range sound. This opens up impedance variation between the drivers meaning each will respond differently to elevated source output impedance – the rule of thumb being that output impedance should be no higher than 1/8th of the impedance of the earphone, any higher and the frequency response will be altered. Linear impedance design (LID) is as it sounds, a circuit that equalises the non-linear impedance of the multiple drivers in the IEM. This means the U6t has a flat impedance curve and will deliver the same sound signature regardless of source output impedance, an invaluable feature for professionals especially who require that consistent sound reproduction. This does not mean the U6t will sound identical from all sources of course, as each can be coloured and showcase different resolving power.
Exclusive Premium Cable
No longer are generic cables accepted as a worthy complement to high-end IEMs and 64 Audio has fully commit to providing a premium experience at every price tier, the U6t is no different. It comes bundled with a new premium cable with a low 0.23 ohm impedance, 7x7x4 multi-twist construction and silver-plated OCC copper wire conductors. It has 26AWG wires making it feel almost like a custom cable in terms of size and sturdiness. Compared to the generic cables of old, the look and feel is in another league.
64 Audio has hugely improved the unboxing experience this generation. You get a large box with outer sleeve adorned with high quality print. The hard box inside opens with a magnetic latch, the inner face of the lid revealing the company’s design ethos with Vitaly’s signature below. Inside lies the earphones and carrying case within a foam inlet. The company have cleverly packaged a card cable winder that means the wires don’t get kinked during storage and unravel easily out of the box. The case is made from genuine leather and features a debossed 64 Audio logo. It’s well-sized and has a soft, non-scratch suede interior. Within lies a 3D printed ear tip holder with 3 pairs of 64 Audio TrueFidelity memory foam ear tips, 3 pairs of SpinFit 155 tips and 3 pairs of generic silicone ear tips. I found the long nozzles of the IEMs would protrude from the aperture of the provided silicone tips and prevent the SpinFit tips from articulating unless only partially placed onto the nozzle. In future, long-stemmed tips such as Azla’s Sednafit range would be a more appropriate complement, but the included options do get the listener started. A separate holder contains the apex modules, two MX and two M20 modules, with the M15 modules being pre-installed onto the U6t themselves. A 64 Audio sticker is another fun addition.
While Custom IEMs offer unmatched fit and comfort, this form factor can be intimidating for newcomers just getting serious about the hobby. However, there have always been significant trade-offs when picking a universal 64 Audio IEM as their shell designs didn’t exhibit the quality of many competitors. This changes with their new generation line-up with all universal models resembling their metal-clad flagships. The U6t specifically is a fantastic looking and feeling IEM, being all-metal with a highly tactile mechanical finish. The gunmetal coat, grey apex modules and gloss embossed faceplates easily contribute to one of the company’s most attractive designs, especially with the new premium cable. I enjoy the aggressive rounding of each edge that optimises ergonomics. Altogether, this forms a refined, premium and aesthetically appealing experience that is an evolution over their past designs.
This is compounded upon with the new cable. As before, 64 are using highly homogenised 0.78mm 2-pin connectors and they are non-recessed, maximising compatibility with aftermarket options. The stock cable is a huge improvement over the dainty, stiff cables of old. It feels more akin to a custom cable in terms of size whilst avoiding becoming cumbersome in terms of weight due to its use of lightweight aluminium connectors. The jacket has minimal microphonic noise transmission or memory but does have a slightly tacky texture and isn’t the most supple I’ve come across. Still, this isn’t something that would garner complaint with most users. I found the pre-moulded ear guides to be well-formed, aiding a stable and comfortable fit. This completes a convincing, high-end IEM experience, joining market leaders from both in BOM and the refinement of their finish.
Fit & Isolation –
If you’re familiar with 64 Audio’s IEMs, you’ll have a similar experience here. Compared to their acrylic shells of old, the new housings have undergone a slight adjustment. With a slightly more aggressive rear taper leading to a more vertically orientated fit, the new shells effectively mitigate my issues with hotspot formation at the back of my ears that I experienced on their original universal shells. The tear-drop shaped shells are reasonably compact and no longer contact much of the outer ear. Their simplistic styling doesn’t provide the locked-in sensation provided by more aggressively sculpted faux-custom shells, but in so doing, they achieve wider compatibility with different ear shapes. I also didn’t find fit stability to be an issue due to their well-angled, elongated nozzles that provide a deeper fit and position the shells in a stable, comfortable position.
The shells aren’t too heavy despite the metal construction and achieved both excellent stability and comfort long-term in my medium-sized ears. That said, I wouldn’t recommend them explicitly for smaller eared listeners due to their height, but they may do with a shallower fit. Seal was not an issue for me but, as above, isn’t especially apparent in terms of sensation. This is because the apex modules vent all wearing pressure, which will be an asset for those sensitive to such. I find this greatly enhances wearing comfort long-term and does indeed alleviate listening fatigue, especially aiding the perception of bass. In addition, added cable noise and the thump of footsteps during commute are significantly dampened by the pressure relief system which makes this a fantastic IEM to use day to day, even for cardio should you be so daring.
Passive noise isolation is good and varies with the apex module installed. The stock M15 modules were fine for daily commute, less attenuating than a sealed monitor but better than most vented hybrid or dynamic driver IEMs. I do think the M20 modules are well-considered for louder environments as you also get a bump in bass which can help to combat ambient noise. Fully sealed modules are available separately but weren’t intended for use with 64 Audio’s IEMs so I cannot comment on these here.