The Astell&Kern AK ZERO1 is what I wanted the TinHiFi T5 and T2 Evo to be even knowing they both target a highly specific market. It's exactly the same market here, but A&K got many things rights. This is a set that prioritizes vocals over instruments, and especially caters to treble-heads that live for the likes of Kpop and Jpop among many other music genres. It's arguably even better with male than female vocals, and the mids are complementary to the overall listening experience, which is clearly tilted towards the higher frequencies without making many want to tear off their ears as with the TinHiFi T5. What this also means is that those who prefer a warmer signature may want to look elsewhere, and the AK ZERO1 certainly is not a set for bassheads. There is a dedicated dynamic driver solely for the low frequency range; however, between the tuning and lackluster technical performance, it's nothing to write home about. EQ doesn't help much either, although your mileage may vary.

The AK ZERO1 is also a set I found to scale quite well with sources, with the most substantial improvement going from a laptop output to, say, a decent portable DAC/amp, such as the Qudelix-5K or iFi GO blu. It's one of the harder IEMs to drive courtesy the complex driver configuration and cross-over network, but that is also a result of the impressive engineering with dedicated, specialized 3D-printed acoustic chambers for each driver type placed inside CNC-machined aluminium housings to make for a well-built set both inside and out. It's a set that gets most things right, but falls short of being excellent for the money in a few regards, including shortcomings in both tonality and technicalities, under others an overly emphasized 5 kHz peak that hurts female vocals as much as it limits the scope of the AK ZERO1 for orchestral music. It's also not the most resolving set, especially for the price range it is going for, and I am not sure whether A&K has the same brand recognition factor it does with DAPs when it comes to IEMs.

Ultimately, it's a set for specific use cases you need to be aware of to figure out whether this is indeed the set for you. I highly recommend going through the entire review to make an informed purchasing decision, including with the accessories, fit and finish, how good a seal you can get with it, aesthetics of the set, and the sound signature, of course. With the AK ZERO1, A&K has set down a strong base for future IEMs under its own label, and I am eager to see the engineering display seen here extrapolated further, especially with those micro-rectangular planar drivers in their unique form factor.