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Astell & Kern AK UW100MKII – 32-Bit aptX Bluetooth IEMs

Astell & Kern AK UW100MKII – 32-Bit aptX Bluetooth IEMs

Astell & Kern AK UW100MKII is a $299 USD pair of Bluetooth TWS or True Wireless IEMs (In-Ear Monitors), with Knowles BA Drivers, up to 29 Hours of Playback, Ambient Mode, and Bluetooth 5.2, sporting a high-end 32-Bit DAC chip inside, and a Premium Qualcomm 5141 BT Chip with aptX Adaptive support. Today we will be reviewing the new bluetooth wireless earphones and compare them to the competition, including HIFIMAN Svanar Wireless (499 USD), Grell TWS 1 (199 USD), and 1More ANC TWS EHD9001TA (199 USD). 



Astell & Kern is a large company from South Korea, best known for their DAPs or Digital Audio Players, being considered one of the best producers of those, especially by those who enjoy high-end music and want to have the most stable user experience, with usually a warmer, more organic sound, and a better resolution than what the competition offers. Astell & Kern did make a few IEMs in the past, and hopefully this year we will get to review every single product that we’ve missed in the past, including the new high-end end DAPs, as well as other Earphones they are working on. There has been an UW100 in the past, since this is the MKII we’re reviewing today, but I have not heard the original, so we will be drawing comparisons with IEMS from other producers. As an Amazon Influencer, I earn from qualifying purchases, and using the purchase links in my reviews helps me maintain this Website and Youtube Channel.

I’d like to thank Astell & Kern for providing the sample for this review, in exchange for my honest opinion. This review is a description of my personal experience.


Product Link

You can grab one from www.amazon.com here – https://amzn.to/47TLdNk

If you’re in the UK, you can grab one from www.amazon.co.uk here – https://amzn.to/49cyB4Z

And if you’re from Europe, you can grab one from www.amazon.de here – https://amzn.to/4bdmdn5


Build Quality/Aesthetics/Fit/Comfort

Astell & Kern always knew how to make a really beautiful looking device and the AK UW100MKII is surely a looker front the moment you open the package. The transport / charging case is super smooth, lightweight, but feels premium and doesn’t have any flex or creaking noise when pressure is applied to it. This is actually an important aspect for any TWS IEM, because you’ll likely use those in a gym setting where you won’t handle them with the utmost care. 

Under the hood, the charging case has about two extra charges above what the IEMs have, but the IEMs have extremely long battery life, being estimated to play for 9 and a half hours, and within my tests being able to easily go beyond 8 hours of playback. The IEM earbuds are also lightweight, at 7 grams, and the case is pretty light too, at 65 grams. 

The DACs inside of each IEM are AKM AK4332ECB, and the whole IEM has a SPL of 94dB. The playback control is touch based, and there are two microphones on each Iem for call quality and for the ambient mode. If you are wearing a cap, it will rub against those microphones and you will hear that amplified when using the Ambient mode, but otherwise you never notice issues with it. The call / voice quality is much better than expected, and my voice came out crisp and clean on the other side, but the microphones pick up wind and noise as well. We have knowles balanced armatures playing inside. We have compatibility with both iOS and Android devices, although only android devices have potentially better bluetooth algorithms, as Apple is still refusing to implement aptX or LDAC in their iPhones. 

Speaking of which, the Bluetooth algorithms supported include SBC, AAC, and aptX Adaptive, with HFP, A2Dp and AVRCP for features. The Bluetooth version is v5.2, but you have to check whether your phone will support those as well, because for example, Samsung S23 Ultra, S24 Ultra, and basically most flagships only support LDAC, and not aptX protocols, which I believe might be part of the reason why the previous version did not receive high praise, as using SBC instead of aptX can heavily gimp the sound you’re hearing. 

Subjectively, the Astell & Kern AK UW100MKII is comfortable, it is lightweight, and the touch control is perfect once you perform the firmware update. It was a bit fiddly before that, but now each touch press is interpreted perfectly. They sit snugly in my ears, and due to the very lightweight design, I can barely feel them. The aesthetic is simply beautiful, and although there is no ANC protocol, the passive noise isolation is pretty high, at around 25 – 35 dB, so you’re fairly well isolated from the outside noise. To be honest, I disable ANC in most IEMs anyways, because for most, it affects the sonic quality, so you will not feel the absence of it, although there is an Ambient mode if you will want to mix some ambient noise with your music, let’s say for hearing something in an office or so. Speaking of office settings, the sound leakage is low, so you don’t have to worry about others hearing your music. There is a separate volume control from the phone, and you use just the right earphone to set the volume, the left being used for setting the Ambient mode. 


Sound Quality

To start the sonic part, I must mention that my main sources for the review have been Samsung S23 Ultra, Huawei P30 PRO, as well as a few other phones, to get the best idea of what the sound is like. aptX Adaptive is great because it allows the IEMS to adapt to how much Bluetooth Bandwidth is available instead of forcing a certain data rate, so the connection is rock solid, but this aptX Adaptive is not available for S23U, so for part of my test I only heard the UW100MKII in SBC mode. The overall sound can be described as smooth, natural, with a deep, warm, but natural bass, natural midrange, and a well extended but natural sounding treble. Everything sounds exactly as if you were not wearing any earphones, the tonality is simply perfect, and it has that Astell Kern house sound that most people rave about, where there is a special smoothness to each musical note. Basically, textures and dynamics are super pleasing, smooth and natural, and the UW100MKII sounds like a really high-end setup with no sonic degradation compared to what you’d expect at a high-end level. If you heard most entry-level Chinese IEMs and TWS Bluetooth Earphones and they all sounded rather V-Shaped or U-Shaped with exaggerated bass and treble, UW100MKII sounds perfectly natural and balanced. There are multiple filter options and those are heavily colored in design, to compensate for the driver and shell peaks and dips in the frequency response. 

While playing with the Astell & Kern App, I noticed that the sound of UW100MKII uses heavy EQ to sound the way it does, and that is okay, no driver is perfect when you consider the fact that those need to put in a DAC, AMP, BT Transmitter and receiver inside a small space, but manages to keep it below 9 grams. The maximum volume is incredibly high, which is pleasing, UW1000MKII reaches 110 dB easily, and it manages to be louder than most TWS IEMs I heard to date, including slightly louder than HIFIMAN Svanar Wireless. I would not make a custom EQ profile, but use one of those available in the AK app for the UW100MKII, they have a bassy profile, balanced and natural profile, with the natural being on by default. For most of the review, I’ve been switching back and forth between natural and balanced, but balanced has been my profile of choice to gauge their sound. 

The bass is clean, goes naturally low in depth, but does not come in a basshead quantity by any means. We have a fairly natural presentation for Pop, and Rock music, maybe some Jazz, but it is too lean and neutral for EDM, Dubstep or Bass Heavy Music in general. The bass has most of the energy between 50 and 100 Hz, which creates a punchy bass but which doesn’t have strong focus on the sub lows. The bass has a bit of warmth, and voices / instruments present a bit of warmth, avoiding a clinical or too sharp presentation / too bright presentation. As Astell & Kern is generally known for a pleasing bass and a smoother sound, it makes sense that their IEMS have a bass that emphasizes those terms. 

The midrange is where most of the magic happens, as it is incredibly natural and voices sound actually realistic, with no pinching or deepening that would make them unnatural. Guitars, violins, all instruments just shine through as if you were sitting in the same room as the singer, and everything just has a magical smoothness, but still with good detail. The soundstage is confined within what I’d consider natural walls, so there is a fair amount of extension in the width and in the depth, but it stays within what I could call natural, not super holographic, but you never feel like it is intimate. A good balance of everything is what UW100MKII has, and that stays true for the instrument separation, which is at the level where instruments are not cut with a surgical precision, but they are still fairly well defined from each other. The upper midrange is at the same level relative to the lower midrange, so UW100MKII will be great for both male and female voices, regardless whether we’re talking about metal like Cannibal Corpse, Adam Levine from Maroon 5, or female voices like Mori Calliope or Takanashi Kiara, or even Jill Tracy. The best instruments played by Astyell & Kern AK UW100MKII are Guitars, Pianos and Violins, where it excels way beyond my expectations, presenting those in a natural, pleasing way, but it was not made for electronic music, synths and the square waves associated with those. 

The reason I am saying it is not great with synthetic music is that the treble is just natural and smooth in amount, although it extends well in the upper treble, but the natural quantity means that square waves and synthetic instruments from literally any EDM or electronic music band will sound a bit too smooth and lean. Naturally, this is a good thing for acoustic music, classical music, and music that’s been recorded in a natural environment as well. It is important to keep in mind that the overall tonal balance is neutral-natural, so you will hear things as if they were played in an open room, with no special over amplification of the low end or the treble, but if you’re coming from a V-Shaped sound or a mid centric sound, UW100MKII can sound either very neutral, linear or a bit bright. 



Astell & Kern AK UW100MKII vs Grell TWS 1 (299 USD vs 199 USD) – Grell TWS1 is one of the very few IEMs that actually implement ANC in such a way that it doesn’t affect the overall sound, and it even costs less than UW100MKII. The comfort is better on the UW100MKII, as they are lighter, smaller and fit better for most ears. We have better passive noise isolation from UW100MKII, but with ANC turned on, TWS1 from Grell can isolate a bit better. The overall sound is more v-Shaped with more bass, and more treble sparkle on the Grell TWS1, which has more depth, while AK UW100MKII sounds more natural in the midrange, has smoother textures and has a bit more detail, but a more intimate soundstage and creates the feeling that you’re closer to the singer. 

Astell & Kern AK UW100MKII vs 1More ANC TWS EHD9001TA (299 USD vs 199 USD) – The build quality is great for both, but the matte plastics used by Astell & Kern give the feeling of premium more than the shiny finish of 1More ANC TWS. Both isolate well from the outside noise, and both have a strong passive noise isolation, but AK UW 100 MKII has a higher degree of passive noise isolation, while 1More has ANC or Active Noise Canceling, which isolates more when you’re in a really noisy environment. The sound of 1More is very traditional for a TWS and Bluetooth IEM, it is sharp, V-Shaped with a strong bass, strong treble, and good detail, but UW 100MKII comes through as having better resolution and actual detail, more refinement, transients are softer and smoother, while the soundstage has about the same width and depth as 1More ANC TWS.

Astell & Kern AK UW100MKII vs HIFIMAN Svanar Wireless (299 USD vs 499 USD) – The only pricier IEM we have in the comparison list is the one that I am actually using the most at the gym, and to be honest I feel better having something with a lot of metal inside for rough usage, but Svanar Wireless is heavier and would often fall out of my ears, so you’d be right to be concerned about the comfort. AK UW100 MKII has a much better passive noise isolation, and with the Svanar I generally just pump the volume to drown out the gym music and replace it with mine. Both are sweat resistant, and I generally don’t take the charging case with me for either, but the sound is very different. Svanar Wireless has more bass and more treble and also supports LDAC, being more compatible with Samsung S24 Ultra, while AK UW100MKII sounds more linear, more natural. I actually prefer Svanar Wireless for the Gym, because the extra bass can get you pumped much better, the extra treble makes them more crisp, and when doing a lot of cardio and physical activity, those are important for your overall experience. On the other hand, AK UW100 MKII is like a proper listening earphone, it is great for music and for a lean, laid back, relaxed experience, it is a great option for those who want to chill and for those who want a portable bluetooth earphone that sounds similar to wired ones. 


Value and Conclusion

The 299 USD price tag may seem a bit high at first, especially considering that most TWS IEMs compete in the 199 USD dollar range, but Astell & Kern manages to provide with a product that is comfortable, has a long battery life, and also sounds natural, which is a rarity in the TWS world. While most go for a U-Shaped or a V-Shaped sound, UW100MKII goes for a natural, clean and relaxed sound that will be easy to listen to regardless how many times you hear it, and which has the resolution, clarity and precision usually expected from the 299 USD price range. 

At the end of the day, if you’re looking for proper resolution, clarity, detail, comfort, and a natural, smooth sound, just as Astell & Kern usually provides, AK UW100MKII is a fully recommended IEM today, which brings a bit of magic in the audiophile world, for those who want to relax, enjoy and have some smooth fun. 


Product Link

You can grab one from www.amazon.com here – https://amzn.to/47TLdNk

If you’re in the UK, you can grab one from www.amazon.co.uk here – https://amzn.to/49cyB4Z

And if you’re from Europe, you can grab one from www.amazon.de here – https://amzn.to/4bdmdn5

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Full Playlist used for this review

We listened to more songs than those named in this playlist, but those are excellent for identifying a sonic signature.  I recommend trying most of the songs from this playlist, especially if you’re searching for new music! The playlists are different for Spotify, Tidal and Youtube, and based on the songs I enjoy and are available on each!




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