Astell & Kern UW 100: high fidelity sound and effective passive isolation


Mis à jour le 12 May 2022.

It’s Astell&Kern’s turn to enter the very prolific market of wireless in-ear monitors. Following KEF and B&W who made their debut in 2021, the South Korean brand is entering the market with the Astell&Kern AK UW100 True wireless IEMs . Sold at €299, these aptX Adaptive compatible IEMs feature a Knowles balanced armature driver and an AK4332 DAC per earbud. Will these IEMs designed for portable hi-fi listening stand out among an extensive competition?

Astell&Kern AK UW100 close up
The Astell&Kern AK UW100 feature the typical aesthetics of the brand and include an AKM AK4332 DAC per earbud.

Packaging and accessories

The AK UW100 come in a compact box adorned with a reproduction of the back of the IEMs. The main specs of the IEMs are listed on the side of the box. The Astell&Kern AK UW100 come with:

  • the charging case
  • the USB-C to USB-A cable
  • five pairs of silicone tips in different sizes
  • the warranty card
  • the user manual


The AK UW100 are the first True Wireless IEMs (Bluetooth with no wire) from the Korean brand primarily known for its audiophile DAPs such as the Astell&Kern A&norma SR25 MKII , Astell&Kern KANN Alpha , Astell&Kern A&Futura SE180 or the Astell&Kern A&ultima SP2000T . So this is not the manufacturer’s trial run when it comes to combining high fidelity and portable audio. The typical Astell&Kern aesthetic catches the eye at first glance with an angular design and the combination of black and anthracite gray. A strong visual identity that can of course be found on the brand’s portable audio players, but also with the Astell&Kern Zero 1 wired in-ear monitors and the Astell&Kern Acro Be100 connected speaker. The charging case also features this design. Relatively bulky compared to the average size of True Wireless cases, this case allows three charges for a total battery life of 24 hours.

Astell&Kern AK UW100 earbuds and case
The Astell&Kern AK UW100 have a battery life of 6 hours and can be fully charged 3 times with the case, for a total battery life of 24 hours.

The AK UW100 IEMs are devoid of active noise cancelation by choice. The manufacturer has clearly announced its decision to override this function to avoid any alteration of the signal and to provide quality passive isolation instead. Passive isolation largely relies on the choice of the most appropriate eartips for the user’s morphology, which is why the Astell&Kern AK UW100 come with five pairs of silicone eartips of different sizes.

Bluetooth aptX Adaptive

The Astell&Kern AK UW100 True Wireless in-ear monitors feature a Bluetooth 5.2 chip compatible with SBC, AAC and aptX Adaptive codecs. The aptX adaptive codec combiens the benefits of the aptX HD and aptX Low Latency codecs to ensure excellent audio and video synchronization as well as high-resolution signal transmission up to 24-bit/48kHz. It automatically optimizes the sound quality and dynamically scale the bit rate to adapt to the tranmission quality to ensure the best possible wireless transmission.

aptX Adaptive Screen Capture
The True Wireless Astell&Kern AK UW100 IEMs automatically connect in aptX Adaptive mode with compatible devices.

Multipoint Bluetooth connection

The AK UW100 are compatible with the multipoint Bluetooth function, which means they can be paired with several devices simultaneously. This feature not only makes it easy to switch between devices, but you can also listen to music streamed from a tablet while receiving notifications and phone calls from your smartphone.

Astell&Kern AK UW100 Multipoint Bluetooth
Thanks to their multipoint Bluetooth function, the Astell&Kern AK UW100 can be connected to multiple devices simultaneously. It is thus possible to easily switch from one device to another, or to watch a video on a tablet while receiving notifications from a phone.

Touch interface, voice assistants and control app

The AK UW100 True Wireless IEMs feature a touch control interface to enable or disable transparency mode, activate the vocal assistant of the paired device, adjust the sound and control playback (play, pause, next track, previous track). Two built-in microphones also allow you to take an incoming call or reject it with a single or double tap on the right earbud. The AK TWS app is an excellent control and customization tool. Not only does it allow you to choose between four levels of transparency when this mode is activated, but it also has an equalization function (four pre-adjusted modes: bass, high, vocal, game), and allows you to change the touch controls on each earbud. The functions ensure a fully personalized and user-friendly experience.

The AK TWS application allows you to adjust the transparency mode, choose a preset EQ and modify the touch controls.

AKM AK4332 DAC and Knowles Balanced Armature driver

The objective of the Korean manufacturer for the Astell&Kern AK UW100 True Wireless IEMs was to prioritize sound quality above all else. In addition to the aptX Adaptive transmission, this is manifested by the integration of a dedicated DAC in each earbud. The majority of True Wireless IEMs use the converter built into the Bluetooth chip. However, these DACs are often developed to be energy efficient, not to ensure the best sound quality possible. The Astell&Kern AK UW 100 use a 32-bit AKM AK4332 DAC per earbud to ensure perfect signal conversion and high-precision sound restitution.

The AK UW100 stand out from their competitors by using a single wideband Knowles balanced armature driver per earbud instead of a traditional dynamic driver. Designed to achieve great precision in the high-mids and high frequency range, this type of transducer is generally a bit more shy when it comes to the low end.

Inside view AK UW100

Key specs

  • Closed-back in-ear monitors
  • Excellent passive isolation
  • Knowles Balanced Armature drivers
  • Touch control interface
  • Control app
  • 4-level transparency mode
  • Compatible with voice assistants
  • Compatible codecs: SBC, AAC and aptX Adaptive
  • Battery life of the IEMs: 6 hours
  • Battery life of the charging case: 18 hours

testing conditions

During our test of the Astell&Kern AK UW100 True Wireless IEMs, we paired them with an aptX Adaptive-compatible Android smartphone. We used our Qobuz Studio Sublime subscription to listen to Hi-Res tracks as well as albums in CD quality downloaded from our Bandcamp collection. In order to test the passive isolation and the transparency function, we used these IEMs in an office, while walking in a busy street and in a store.

While the earbuds are fairly easy to place once the insertion/rotation gesture is acquired, we found that the AK UW100 were not the most comfortable IEMs after a while. Because of their imposing size and their angular design, the earbuds can cause some discomfort, espacially for people with smaller ears. This is not an absolute deal breaker if you’re using them during a one to two hour commute, but it can affect the overall listening comfort for some people when using these IEMs throughout the day or on a long plane ride.

AK UW100 detail
The Astell&Kern UW100 True Wireless in-ear monitors are quite imposing and stand out from their competitors at first glance.

Listening impressions

The AK UW100 True Wireless IEMs quickly won us over with their clarity and spacious sound stage. These qualities which are typically found with balanced armature driver are however not tarnished by a lack of bass as one might think due to the use of a single balanced armature driver per earpiece. While it doesn’t have tremendous weight and impact, the low end tight and audible even when the EQ function is deactivated. Once the “bass emphasis mode” activated, we found that the lows were surprisingly textured and deep without being excessive. Using a dedicated converter per earbud clearly pays off. With a spacious and well layered soundstage, the AK UW100 sound very natural. We really felt like we were immersed in the heart of the music, surrounded by the rich tone of the various instruments. The first guitar chords of the track Zero Day (Qobuz 24-bit/88.2kHz) by the band Nothing sounded strikingly natural. When the rest of the band joins in, the soundstage filled up without giving the impression of narrowing down while vocals sat on top of the instruments without losing the slightest detail. The two guitars, placed on either side of the soundstage, were delivered with a precision that brought this track to life.

Astell&Kern AK UW100 Qobuz - Nothing
Thanks to their support for the aptX Adaptive codec, the Astell&Kern AK UW100 guarantee optimal wireless transmission quality.

On the track Freddie Freeloader (Qobuz 24/192) from Miles Davis’ Kind of Blue, the UW100s brought up their A game when it comes to sound placement. As Davis’ trumpet travelled from side to side, we could clearly hear the drums to our right, the piano to the left and the double bass right in the center. Each element was surrounded with all the space necessary to hear the faintest of nuances.

Mission accomplished for the manufacturer who wanted to do without an active noise cancellation function. The passive isolation is excellent and the association with the very effective transparency mode makes these True Wireless IEMs very versatile travelling companions as they can be used in noisy environement or a quiet office alike.

Astell&Kern AK UW100 Qobuz - Miles Davis
The wide sound stage and precise sound placement of the Astell&Kern AK UW100 allow the listener to dive straight in the heart of the music.

The equalization modes fulfill their role perfectly. They skillfully complement the performance of IEMs which are already comfortable with all the styles of music we listened to. A customizable EQ mode for even more versatility would have been the icing on the cake. We noticed no latency with videos, which mean they can be used to watch movies and series on a compatible, smartphone, tablet or computer.

Compared to…

B&W PI5 : sold for €249, the PI5s are heavier than the Astell&Kern AK IEMs. However, the B&Ws are more comfortable thanks to a design that sits better in the ear. They are also marketed as True Wireless IEMs designed for hi-fi listening and benefit from a noise cancellation function as well as a proprietary DSP, but they fail to match the AK UW 100’s precision and impression of spaciousness. The B&W PI7 earphones are the real rivals of the AK UW100s, but the 100 euro difference between the two models is an argument that will tip the scales in favor of the AK UW100s for many people.

Klipsch T5 II True Wireless ANC : the Klipsch IEMs have longer battery life and feature an ANC function. They will more easily appeal to users with longer commutes. In terms of sound performance, the Astell&Kerns undeniably have the upper hand. With their separated DAC, wideband Knowles drivers and aptX Adaptive Bluetooth support, the AK UW100s rank among the best in their class when it comes to sound quality.

AK UW 100 lifestyle 002
Like the brand’s portable audio players, the Astell&Kern AK UW100 are among the best True Wireless IEMs in this price range when it comes to musical performance.

Who is it for?

The Astell&Kern AK UW100 in-ear monitors are intended for music lovers looking for quality listening while being completely free of wired connection. However, users who find it difficult to fit relatively large earbuds in their ears should ensure that prolonged listening does not cause discomfort. Particularly recommended with a source compatible with the aptX Adaptive codec, the AK UW100 manage to hold their own by placing themselves among the best True Wireless hi-fi IEMs in this price range.

AK UW 100 lifestyle 003
With the AK UW100, Astell&Kern decided to replace active noise cancelation with an top-notch passive sound isolation and clearly made the right choice.


While we found the ergonomics perfectible, it is far from being a deal breaker. The The Astell&Kern AK UW100 rich, balanced and detailed sound as well as their sense of scale are strong arguments in their favor. We never felt like the ANC function was lacking as their passive insulation is effective. Musically speaking, the manufacturer has achieved a real feat by combining an AKM DAC with a balanced armature driver in each earbud.

What we liked

  • The spacious soundstage
  • The balanced and natural sound
  • The very effective transparency function
  • aptX Adaptive support
  • The passive isolation

We would have liked

  • A more compact and less angular design
  • A band equalizer function in the app
  • An active noise reduction function would have been a plus considering the price

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Amateur de disques vinyle et passionné d'obscurs sous-genres musicaux, mes préférences cinématographiques s'orientent vers les films d'horreur, des classiques Universal aux slashers et films fantastiques des années 80, ainsi que vers la période américaine d'Alfred Hitchcock. Côté matériel je privilégie une installation hi-fi épurée et sobre pour l'écoute de supports physiques et l'utilisation d'un ensemble DAC / écouteurs intra-auriculaires pour les plateformes de musique dématérialisée telles que Qobuz et Bandcamp.

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