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AK Zero1 IEM sitting on a sink handle in Black and White

Review: Astell & Kern Zero1 Earphone/IEM

Disclaimer: I would like to formally thank Eileen from Astell & Kern (Dreamus Company) for graciously providing us with the Zero1 for review. I am not affiliated with Astell & Kern, and the views shared below reflect my honest thoughts surrounding the product.


  • Excellent industrial aesthetics and design
  • Impeccable build quality outclassing counterparts in a similar price point
  • Greatly-extended highs with exceptional microdynamic detail retrieval
  • Class-leading bass control with little to no audible distortion
  • Strong sound staging and imaging capabilities


  • Angular design can result in long-term discomfort in the concha
  • Midrange scoop results in aberrant timbre with a metallic artificiality
  • Unforgiving of poorly-mastered tracks
  • Over-excitable presentation in treble exaggerates harsh peaks


The Early Daze

Astell & Kern’s (endearingly known as AK) historical pedigree for luxury audio, especially to millennial audiophiles, needs no further introduction. For readers unacquainted with the AK trademark, Astell & Kern was one of the earliest progenitors forging the unforeseen path forward in the audiophile niche.

Formerly known as IRiver, the South-Korean company opened its doors in 1999 as Dreamus Company’s consumer-electronics division for a domestic audience. IRiver’s heydays were established on the constant research and development of early Flash and MP3 players nascent in the dawn of portable media devices. In 2013, IRiver made the radical decision to form Astell & Kern, a subsidiary brand paving the way for the fiercely competitive luxury digital audio player market we hold near and dear.

Courtesy: Astell & Kern

My memorable first encounter with Astell & Kern was with the universally lauded AK100 DAP in 2014. At the time, the audiophile hobby was still finding its mojo, and balanced audio topologies were exclusive to a few audio purveyors like Astell & Kern and IBasso. And the AK100 was the proverbial gateway drug to the promising DAP scene and its measurable (and perceivable) influence in the signal path. Granted, the AK100 was priced close to $799, which was unheard of. The same can’t be said about today! Balanced DAPs are plentiful as the DAP arms race to the bottom (and the top).

But it would be callous of me not to acknowledge the over-the-top premium craftsmanship and intelligible design the AK100 had going for it. If the iPod Classic was considered a luxury creation, the AK100 is what I would classify as hyper-luxury. The AK100 is finished to a degree comparable to a luxury car, with bold edges tracing the sleek silhouette of the DAP with an aluminium-finished chassis with parallel brush marks. Every facet of the DAP was an aesthetic match made in nirvana, and the navigational knob was an absolute joy to use.

Astell & Kern spared no expense from the drawing board to the factory floor. And that philosophy hasn’t changed.

Where Astell And Kern Are Today

Leapfrog a decade later, and Astell & Kern remains a steadfast pillar in the audiophile scene, releasing designated lineups of DAPs in different price segments for discerning audiophiles to pick from. From the Kann to the Norma ranges, there’s a player for everybody. Interestingly enough, Astell & Kern started to pivot into the IEMs and headphone arena, selectively collaborating with star-studded companies such as Campfire Audio (Solaris X, Pathfinder), Jerry Harvey Audio (Billie Jean, Diana), and Beyerdynamic (T8IE, T9IE). Leveraging their combined, Astell & Kern has gained invaluable first-hand experience in the meat-and-bones of IEM design and manufacture.

That was when Astell & Kern’s Eureka moment came to fruition. The incalculable years of knowledge gained culminated in the birth of the Zero1: Astell & Kern’s first official IEM. With no input from external vendors or brand heavyweights, the Zero1 is proudly theirs and theirs alone. Priced at $699, the Zero1 is a watershed step towards complete autonomy and independence in IEM design. The Zero1 comes in two colourways: Silver and Black.

Today, we examine Zero1 Special Edition Black (with a 4.4mm terminated cable) and see if it stacks ups to the merits espoused by the South-Korean brand. The Zero1 can be purchased from Astell & Kern’s official store.


Usually, I don’t dive deeply into the driver configurations or topologies under the hood of an IEM or headphone. In this instance, the Zero1 boasts an unorthodox tribrid configuration warranting further discussion.

Courtesy: Astell & Kern

In the above break-down view of the Zero1, we can see that the Zero1’s driver array consists of one micro square panel (or planar magnetic driver) the size of a standard balanced armature, followed by two custom coiled balanced armatures tuned and manufactured to Astell & Kern’s rigorous specifications, and one 5.6mm dynamic-driver. By tuning each driver to fit Astell & Kern’s parameters, they can effectively tune and implement a crossover network that best optimises overall sonic performance.

All four drivers are mounted in a 3D-printed acoustic chamber — reminiscent of Campfire Audio’s acoustic chamber tuning methodologies. According to Astell & Kern, doing this circumvents unnecessary resonances, distortion and unwanted audible artefacts.

To my knowledge, there aren’t many tribrid IEMs in the market, save for the enigmatic QDC Folk. But given the Zero1’s earlier release date, the Zero1 was (probably) the revolutionary attempt at a tribrid configuration.

Onto the next page for details on build quality



Kevin Goh

Kevin Goh

Raised in Southeast Asia’s largest portable-audio market, Kevin’s interest in high-end audio has grown alongside it as the industry flourishes. His pursuit of “perfect sound” began in the heydays of Jaben in Singapore at the age of just 10 years old. Kevin believes that we live in a golden age of readily accessible, quality audio.


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