Astell&Kern Zero 2 Review: Sugar-free Sweetness

Astell&Kern Zero 2 Review: Sugar-free Sweetness

If you’re into portable audio, Astell & Kern is one of those major brands you’ve most likely heard of. Although they’re known for manufacturing portable audio players, Astell & Kern has been continuously co-developing earphones with different in-ear brands. JH Layla Aion, Campfire Audio Pathfinder, and the most recent Vision Ears Aura are some of the many examples.


While these in-ears were manufactured by different brands and countries, they all share the same fact that they are tuned and designed by Astell & Kern. However, we can’t call these Astell & Kern earphones because they are after all collaboration projects. 


In recent years, Astell & Kern finally began to fully tune and manufacture the IEMs by themselves and created a true AK IEM: the Zero Series. The first AK IEM is called the Zero 1 and recently they’ve announced Zero 2 which we’ll be reviewing today. Let’s test the sound as well as compare it with Zero 1.



Just like most other AK products the packaging is quite simplistic. With a monochrome color theme and clean presentation, the package box includes the Zero 2 IEMs, 2 stock cables, 6 pairs of silicone tips, and a leather case.      


Four different types of driver

Zero 2 is a quad-brid IEM that boasts a complicated combination of different drivers, using a 10mm dynamic driver, a piezoelectric transducer, 4 custom BA drivers, and a planar-dynamic driver. The internals are precisely built with 3D-printed sound chambers that hold the driver in place. Below are the specific drivers that comprise the inside of these earphones. 


Lows & Ultra-highs: Dynamic driver + Piezoelectric transducer

Zero 2’s driver setup is quite interesting. A dynamic driver and a piezo driver are fused yet each drivers are designed to play different frequency ranges. The 10mm dynamic driver plays the low-frequency while the piezo works as a super tweeter. This combination of drivers moves together to play different frequency ranges.  


Sub-bass & Full-range: 4 Coil Parameter BA drivers

The frequency setup for the BA drivers is also quite unorthodox. Zero 2 uses 4 proprietary Coil Parameter BA drivers which are custom designed by Astell & Kern. These drivers are built to effectively play two different frequency ranges, allowing these 4 BA drivers to cover both sub-bass and full-range.      


Super Tweeter: Micro Rectangular Planar-Dynamic Driver

This long-named driver is one of the newest driver formats that’s been introduced to the earphone industry. Planar drivers are known for having excellent treble performance yet their bulky size has limited its usage for hybrid IEMs.    


To solve this issue, after significant R&D and research, Astell & Kern has presented this new type of driver for the first in the industry. This driver has miniaturized and modified the conventional planar driver, then housed in a rectangular chamber that resembles the shape and size of a balanced armature. The planar diaphragm is applied with polymer and thin metal films, further enhancing the treble extension.   


Earpiece: Light and Shadow

The earpiece design well reflects the design concept of “light and shadow” that Astell & Kern desires. The texture grains, edges, and curves of the earpieces make the light reflect and spread in gradience. The faceplate is finished in grainy silver with an edgy design while the inner side is finished ergonomically with matte black coating.


Zero 2 is fully built with CNC aluminum for durability and prevention of resonance. It uses MMCX connectors which is a slight disappointment as I’d rather use the more popular 2pin connectors. The fitting was questionable by the looks yet the actual fitting experience wasn’t bad. It was better than my expectation at least.


The earpieces are slightly bulky and the nozzle length is on the shorter side, so using a slightly larger eartip would be recommended. If you have smaller outer ears the fitting might come as an issue, yet I expect most to have a decent fit.     


Two stock cables

The IEMs come with two stock cables each terminated in 3.5mm and 4.4mm connectors. Astell & Kern was the leader of 2.5mm connectors though seems like they’ve finally decided to remove the 2.5mm option as the 4.4mm connectors became the mainstream for balanced output. I still enjoy using 2.5mm, so this change is rather unfortunate.


Cables are made of high-purity, silver-plated OFC wires with quality metal parts. The stock cable is quite good in both sound and usability. The connector parts feel sturdy and light in weight. The wires are very pliable and don’t cause microphonics either.    


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