Astell & Kern AK UW100MKII review – lots of promise, squandered

AK UW100MKII Two-minute review

The new AK UW100MKII are a hair’s breadth from being some of the best wireless earbuds on the market right now, but one major issue – and another problem that’d be a major one if the other didn’t exist – stop the right in their tracks.

The latest buds from South Korean premium audio company Astell & Kern, the buds sit alongside other audiophile-friendly products from the company, including DAPs, big-budget speakers and four-figure-price wired headphones. That should give you an impression of where A&K's latest proposition is targeted: these are top-end wireless earbuds.

You can tell when you listen to the AK UW100MKII – they sound absolutely fantastic. Audio is incredibly high-quality, detailed and balanced, enough to automatically place the AK amongst the best. So why only 2.5 out of 5? 

The main issue (and it's a big one) comes from the UW100MKII’s design, as the bulky buds simply refuse to stay in the ear for long periods. That’s true even when you’re sitting still in a seat, but it can be dangerous when you’re out and about, with one ill-timed head turn or jump over a puddle causing these premium buds to fall into the drink or down a street grate, out of view.

I can’t overstate how annoying it was to have the buds constantly plummeting to the ground when I was trying to enjoy music; A&K offers five different silicon tips of different sizes in the box, yet none fixes the issue that these giant earbuds provide.

Even when the earbuds aren’t escaping and sliding to earth, they seem to think that they are. The errant wearer detection would constantly pause music, thinking that the earbuds were no longer in my ear, even when I hadn’t even touched them. The AK UW100MKII really don’t want you to listen to music, apparently!

It’s a great shame, because without those two issues, the AK UW100MKII could be best-in-class contenders. The feature set is rounded out by a fantastic EQ app that lets you fiddle with audio to your pleasure, incredibly responsive touch controls that’ll have your AirPod- or Samsung-bud-toting friends jealous, and an impressive battery life that beats many rivals.

That could all bring the score up to 3 stars, but what stops the AK UW100MKII from getting that round figure is the price of the buds. They’re priced at a level that’d be justifiable for the audio quality you’re getting, but that just seems galling if you can’t listen to music for more than 15 minutes at a time.

I can begrudgingly recommend the UW100MKII if you’re only going to listen at home, and have the money to spend on this pricey home-only pair. But if that’s not you, there are countless preferable rivals.

AK UW100MKII review: Price and release date

• Released in October 2023
• Officially priced at $280 / £269 (roughly AU$340)

The AK UW100MKII are certainly not cheap earbuds. They cost $280 / £269 (roughly AU$340) when they were released in October 2023, and while you can find small discounts from third-party retailers occasionally, that’s generally the price you’ll pay for them.

At that price, the AK buds cost more than the Apple AirPods Pro 2, Sony WF-1000XM4 and, in the UK at least, the Technics EAH-AZ80, which we call the best premium earbuds in our round-up of the best wireless headphones.

AK UW100MKII review: Specs

AK UW100MKII review: Features

• Useful tie-in app
• Responsive touch controls
• Inaccurate wearer detection feature

The AK UW100MKII use Bluetooth 5.2, which isn’t quite the top standard, with 5.3 offering slightly reduced power consumption and lower latency, but the honestly the difference is largely negligible. Not once in our testing period with the AK did they lose connection or drop without reason. Initially the pairing process was a little fiddly, with my phone not recognizing the buds until I restarted both it and them, but afterwards it all worked peachy.

Of course, you can choose to set up the A&K app to gain a few extra features. Using this means you get to change what the touch controls do, play with EQ including creating your own custom set-up, and change the strength of ‘ambient mode’, a transparency mode letting you hear your surroundings.

There’s no active noise cancellation (ANC) here, with Astell & Kern instead opting for traditional passive noise isolation (PNI), which is arguably better at removing high-frequency noises but therefore struggles at the low end and with the constant thrum of everyday life.

The UW100MKII have a feature common in true wireless earbuds: automatic wearer detection, so they can pause music when you remove them and resume it when you put the buds back in your ear. 

That’s how the feature works in theory, but in practice it often erroneously thought I’d removed the buds when I hadn’t. I had to keep manually restarting my music; it only happened every hour or so, but it was still annoying enough that it’s imposible not to flag or to not affect the overall star-rating. I’d suggest it was only an issue with my review unit, however other reviewers have also raised the problem. Thankfully, you can toggle wearer detection off in the app – and I’d strongly advise you do so straight away.

Another common feature in buds is touch controls, but far from it not working well here, these could actually be some of the best-in-class headphones for on-ear touch functionality. You can tap on most parts of the earbuds to pause or resume your music, and not once in testing did they fail to recognize a press. The command is carried out quickly, with a gentle chime to let you know that it’s happening and you don’t need to press so hard that you shove the bud further into your ear. I often avoid earbud touch controls but these had me gleefully using them.

A&K cites a battery life for the buds of 9.5 hours, and in our testing this seemed roughly right. Using the charging case you can boost this up to 29 hours, and overall that figure matches or exceeds quite a few premium rivals in the market. For context, the AirPods Pro 2 have a 6-hour bud life and 30-hour case life. 

The USB-C port in the charging case lets you power up the buds quickly, but you can also use wireless charging to power up these buds too. That can be especially useful if you have a smartphone with reverse wireless powering, which means you can turn the phone into a powering pad to boost other tech.

• Features score: 3/5

AK UW100MKII review: Design

• Large buds are prone to falling out
• Unique appearance for buds and case
• Fairly large charging case

The UW100MKII just look a little different from other earbuds on the market (well, except the inaugural Astell & Kern AK UW100 buds).

This starts with the case: it has a hexagonal body that makes it resemble a futuristic-looking treasure chest more than somewhere you’re meant to store headphones. That’s doubly the case when you lift up the lid, which turns on the cyan LED strip. Weighing in at 65g, it’s a little on the large side, but we’ve seen cases that are a lot bigger too.

The earbuds themselves continue this unique design: they’re large and pentagonal, with a tapered, pointed end that continues the sci-fi theme. If you want earbuds that make it look like you’re living in a cyberpunk future, these fit the brief. However, this large housing contributes to the UW100MKII’s deal-breaking issue. 

In my testing time with the A&K buds, they would frequently fall out of my ears. Most frequently this was when I was walking, bobbing up and down, but they’d even tumble out if I was sitting still or simply moving my head. In an attempt to remedy the issue, I tested each of the five differently-sized replaceable tips that come with the headphones, but none fixed the matter.

If I were to speculate on why the UW100MKII were so keen to test the pull of gravity, I’d say that it’s the fault of the giant earbuds. Despite only weighing 7g, the large size drags the buds down and makes a secure fit impossible.  

Given the tech packed into these second-gen. A&S earbuds, their large size is perhaps justifiable, but it’s hard to enjoy top-quality audio when they are constantly falling out.

• Design score: 2.5/5

AK UW100MKII review: Sound quality

• Fantastic audio quality
• Customization options
• Max volume could be higher

Finally, we can move into ‘praise’ territory for the AK UW100MKII – and it’s well-deserved praise because they sound absolutely great.

The spec sheet is a veritable who’s who of audio-improving features and tools. There’s A&K’s home-brewed AK4332ECB DAC for improved conversion of digital information into music; multiple Bluetooth codecs including AptX Adaptive and AAC, a Qualcomm-made Bluetoooth chipset, a driver made by Knowles and more.

You don’t need to know what any of these individual entries mean, other than the fact that many different companies have contributed their expertise to the buds. And it shows.

The UW100MKII have a surprising level of sound quality for wire-free earbuds. You can hear the squeaks of guitars as players move their hands, individual notes in chords, different parts of harmonies, instruments as they fade instead of just dropping out. It’s really easy to enjoy music when you can hear all of the components separated and celebrated like this.

The bass sounds crisp and impactful, even when you haven’t boosted it using the app's EQ tab, but it never overpowers the treble in music.  The soundstage is also impeccable – if you close your eyes, you can almost imagine a live band performing the music in front of you.

The ability to fiddle with, and customize, the EQ may appeal to particular audiophiles. I didn’t use it to augment my testing other than to test the efficacy of the feature itself, but was impressed by what I heard – some headphone EQs barely affect the music, but there was a palpable change when I fiddled with the bass or treble.

If I’ve one note – and it’s a fairly minor one – it’s that the maximum volume could have been a little higher. It’s fine for when you’re listening in a quiet room – I generally listened one tier below maximum in this setting – but if you’re out in public or somewhere noisy, it’d be nice to be able to bump up the volume a little more, especially with the lack of ANC. 

• Sound quality: 4.5/5

Should you buy the AK UW100MKII?

Buy it if…

Don’t buy it if…

AK UW100MKII review: Also consider

Apple AirPods Pro 2
Apple's top-tier premium headphones may not have world-beating sound quality but they have a longer case battery life, lighter bud weight and lower price than Astell & Kern's newest. They really are Apple-centric, though.

See our full AirPods Pro 2 review

Technics EAH-AZ80
These premium headphones are chock-full of useful features and although they don't quite compare with the A&Ks from an audio perspective, they won't flee from your ears at the slightest provocation either.

See our full Technics EAH-AZ80

How I tested the AK UW100MKII

• Tested for two weeks
• Largely tested at home, though with some excursions

The overall testing period for the AK UW100MKII was two weeks, not including writing time for the review itself.

After first setting up the earbuds, it quickly became apparent that they wouldn't reliably stay in my ear, even after I tried every single one of the other sized silicon tips included with them. For this reason I conducted most of the testing from home, for fear of the buds falling out somewhere – and me not being able to retrieve them. I did take the AK UW100MKII on a few trips around my neighborhood, just to be able to test the passive isolation out in the wild though.

I mainly tested the buds by streaming music from Spotify, but also watched TV shows on Netflix, played a few mobile games and conducted calls through the buds, in order to test them in a variety of circumstances.

I've been testing tech for TechRadar for nearly five years now including earbuds, headphones, smartphones, tablets, ereaders, speakers, smartwatches, even electric scooters; I've got plenty of experience reviewing and comparing products.

• First reviewed in January 2024