Astell&Kern AK Zero1 Review

Astell&Kern AK Zero1 Review

While their name is almost synonymous with high-end portable audio – and they’ve collaborated with other brands on several IEMs and headphones – Astell&Kern had yet to create their own original IEM…until now. The AK Zero1 is Astell&Kern’s first IEM, and it looks to take Astell&Kern’s reputation for incredible, premium DAP designs and translate it into an earphone. While they certainly captured their signature look in the AK Zero1, can it deliver the sound?

Build and Design

AK Zero1’s aluminum shells look like they could have been cut right off of an Astell&Kern DAP. Crafted in Japan, they have an excellent build quality and feel. The MMCX cable has similarly machined aluminum hardware that matches the IEM shell nicely, and the construction is silver-plated oxygen free copper. Also included is a selection of silicone eartips, and a leather case. The cable, shells, and the overall package could honestly be for an IEM that’s 3x the price and gives a very strong first impression.

Astell&Kern AK Zero1

In terms of fit, the nozzles are fairly long, and with both the provided eartips I ran into some trouble getting the right balance for a comfortable, stable fit, and a good seal. If you don’t like the deeper insertion depth for a seal, you can use a larger sized ear tip, but I found that you sacrificed some stability with that method. You can definitely get a good seal, but it may take a  little bit of tweaking to find a comfortable fit for your ears.


Astell&Kern has been describing Zero1 as a hybrid, but it’s technically a tribrid, featuring three driver types: one dynamic, two balanced armature, and a planar driver (in a pear tree). Zero1 makes good use of all three driver types with a sound that is nimble, dynamic, and highly detailed.

The dynamic driver is on the smaller side at 5.6mm, but it delivers a sort of “best of both worlds” sound that captures some of the speed and accuracy of balanced armature bass along with the impact and timbre that only a dynamic driver can provide. The bass also has good extension into the lower regions, and an overall balanced feeling that gives you depth, dynamics, and detail all in good measure.

Astell&Kern AK Zero1

The lower mids provide some texture to the bass, and as you move up the frequency band, there’s a slight recession, but still strong vocal presence and good clarity. The treble has smooth presentation but with the strong resolution in the highs typical of high-end planar magnetic headphones.

In terms of the 3D image, the soundstage is moderately sized for an IEM, with a good sense of depth and width, but not particularly large. The imaging is very strong, and definitely a highlight at this price point, along with the resolution.

Listening to “Roundabout” by Yes, you get a great “pluck” effect with the acoustic guitar in the intro. When the full band comes it, everything is strongly separated, with loads of details being presented, from the pick noise on the guitar harmonics to an extra bit of grit on the bass. The vocals are well placed and balanced, if not strongly highlighted. Zero1 provides the speed, resolution, and definition to appreciate Yes’s intricate arrangements and deft playing. 

Zero1 captures the almost lo-fi throwback vibe of twenty one pilots “Good Day” in a way that both makes the song feel like it’s right out of the 70s while subtly revealing the modern production values behind the curtain. The textures and sounds feel like they’re pulled off an ELO album, but the presentation of the 3D image and positioning showcases the 21st studio century production. The analog warmth of the organs and synthesizers envelops the listener, while a tight, snappy drum kit sits right behind the singer. The piano is full-bodied with just a touch of honky-tonk twang. Zero1 also shows you new textures and sounds you missed on subsequent playthroughs, revealing how densely packed and produced the song is.

Astell&Kern AK Zero1

B.B. King’s “Same Old Story (Same Old Song)” is brilliantly detailed and crisp. Flanked by acoustic guitars, bass, and backing vocals, the King of Blues and his guitar are dead center. The guitar licks are clean and smooth with a touch of bite. King’s vocals are detailed, but set a little bit back from the guitar. The drums add punctuation, and are further back in the mix. Again, the key here is the strong separation, and clean delivery without any congestion as the various parts weave in and out of each other.

On “Shake it Off” by Florence + The Machine, the lead vocal is up close and intimate – loaded with feeling and texture. The thick textures in the bass and lower mids make this a song prone to muddiness, but Zero1 continues to demonstrate strong separation, delivering a warm low end and big, emotional vocals without losing its coherence. The production of the song provides a somewhat heightened feeling of width and size which pushes against the limits of Zero1’s soundstage at times, but overall the presentation of size and scope is strong.

Mini-Review: Astell&Kern SR25 MKII

Astell&Kern accompanied the launch of the AK Zero1 with an update to their budget friendly SR25 DAP: the SR25 MKII. The MKII gives you the same basic design, with some hardware updates as well as some very important software updates that follow-up new features from the launch of the SP2000T earlier this year.

SR25 has always been a small form factor, and along with that, it has a smaller screen. In terms of the basic usability of the SR25 MKII, the operation feels generally responsive. This isn’t going to be a flagship smartphone type experience, but it doesn’t feel sluggish. The main drawback is just that the screen is small, so if you have large hands, you’re probably going to fat-finger a bit when using the keyboard. The hardware controls and buttons are up to Astell&Kern’s high standards, with a good feel and solid design. The volume wheel has just the right level of resistance and a nice clicky feedback.

Astell&Kern AK Zero1 SR25 MKII

While all of that is mostly the same, the big update is the addition of a few key features. One new feature is ReplayGain, which normalizes the volume across your collection for playback, and the addition of a 4.4mm output, which expands your headphone options. The really big deal – for me at least – is the addition of direct downloads for supported apps, just like on the SP2000T. That means you can purchase the DAP and immediately download the full version of select streaming apps, like Qobuz, Spotify, and Amazon Music, without having to go through the old song and dance of copying APK files from your computer to the player.

In terms of the output, MKII refines aspects of SR25’s sound, but doesn’t stray too far from the original tuning. There’s a touch more presence in the highs, along with a tighter feeling bass, and maybe an overall sense of slightly stronger resolution.

While there are improvements all around, the real standouts in the SR25 MKII are the addition of the 4.4mm output (which is becoming the standard for balanced mobile headphones) and the availability of streaming apps for direct download onto the player. If you’re in the market for a premium DAP experience on a budget, the SR25 MKII delivers some of the best of Astell&Kern at a great price.

Comparison: Final B1, Campfire Andromeda

For comparisons, the most obvious was the Final B1, which shares a number of attributes with AK Zero1, ranging from its metal finish and silver cable to aspects of its tuning. As AK Zero1 clearly has some IEMs in the next price bracket up in its sights, the Campfire Andromeda seems like the perfect representative for IEMs from the next tier up.

In terms of packaging and accessories, I’m a little bit partial to Campfire’s presentation (and their very high eartip count), but all three have some nice features. B1’s case is slimmer and more pocketable than the others, and AK Zero1 just has the A&K luxurious feel to the experience. The build is also quite close between the three, with aluminum and stainless steel being the metals of choice. AK Zero1 has perhaps the best look and feel on the cable, but all three provide a very high-end look and feel from top to bottom.

The sound is where things get interesting. Andromeda has excellent bass extension, and a fast tight response, but not quite the same level of physical punch as the other two. B1 is the most suited for bassheads, with its wide, thick bass with plenty of dynamic driver punch. Zero1 splits the difference with the speed and depth of Andromeda, but some of B1’s dynamic, physical impact.

Astell&Kern AK Zero1 Final B1

Andromeda’s mids can’t really be beaten, with a well balanced, detailed presentation that shines with a wide-range of instruments and vocal styles. B1 has strong detail, but also has a bit of bleed in from the bass that can muddle the lower mids. Zero1 doesn’t have any notable negatives in the mids, it just doesn’t reach the same heights as Andromeda.

In the treble, B1 has good definition, but not quite the same extension as Andromeda, and Zero1’s planar driver gives it very strong resolution, but it’s not as resolving as Andromeda. The soundstage and imaging on B1 or Zero1 are also just a couple steps behind Andromeda’s holographic presentation.

While Andromeda has hardly found itself unseated, B1 and Zero1 are no slouches, with Zero1 in particular demonstrating a strong, balanced performance that helps secure its status as a strong contender with excellent value for the price.

The Bottom Line

With a sound that balances tight, deep bass with a liquidy treble that’s both smooth and resolving, AK Zero1 demonstrates that Astell&Kern’s expertise in tuning DAPs has clear applications in tuning IEMs as well. When you put the whole package together, you get a beautiful material and sound design that lives up to the legacy of products like the SP2000 while providing incredible value in an IEM.