Review - Kiwi Ears Allegro

Review - KZ S2 (TWS Sub 50€)

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Also available on YouTube in Spanish: Acho Reviews YouTube 

I ordered the KZ S2 from Indiegogo when they were first launched, for a super early bird price of around 20€. I opted for the white finish as I don’t have any white IEMs (at least I don’t think I do) and they took a while to make it here due to waiting for them to go into production and then shipping issues with the pandemic etc. but they finally made it and after a few weeks of using these true wireless IEMs, here is my review.

Build and comfort…

It has been a while since I received any KZ products but it seems that the packaging and presentation has not changed much since I received the ZS10 Pro and the ZSN Pro last year.

A standard white box with an outline of the IEMs on the outside opens up to find a simple white case in which the IEMs are contained. Under the plastic insert in which the case sits, there is a short USB C charging cable, a couple of set of silicone tips and an instruction booklet.

My first impression is that they look pretty cheap, both the case and the IEMs, in a plain white plastic with “KZACOUSTICS” printed on the case and the drive count printed on the IEMs in silver lettering. After while though, the look of the IEMs has actually grown on me, but I still think the case looks very cheap, then again, to be fair, they are very cheap!

The case is pretty light, mainly because of the plastic build and the fact that it contains a battery of only 500mA. There is no quick charge function, either for the case or the IEMs, and for some reason they have decided to put the USB C connector on the bottom of the case, meaning you need to lay it down to charge it. This is not a huge issue but may mess with some peoples OCD.

Having the case laid on its side to charge also means you need to use both hands to remove the IEMs from the case but I have found this to be true even when not charging, I have not yet managed to master the technique of removing them from their case without using one hand to hold the case and the other to pull out the IEMs.

The spaces in the case are large enough to take the IEMs with foam tips but it is a good idea to make sure they are seated correctly and charging (the red lights are on). I haven’t tried them with anything larger than foam  but my guess is that they wouldn’t fit in the case correctly.

The IEMs themselves are small and light, which makes comfort nice as far as weight goes, although due to the shape of them, the top part rubs against my ear and causes some discomfort after extended use. That is obviously a very personal thing due to my own ear shape, everyone is different and this may not be an issue for your ears (or you may find them very uncomfortable) so each will have to reach their own conclusions on that one.

I have mentioned in basically all of my IEM reviews that I prefer foam tips, however, for some reason I actually prefer silicone tips on the S2, finding them more comfortable.


A drawback about how light the case and the IEMs are is in regards to battery life. As I mentioned above, the case only has a 500mA battery and in the IEMs it is 40mA. This means that playback is not that long. I believe KZ claims up to 4 hours of listening time plus another 14 hours when charging from the case. As they say “Up To”, I don’t know at what volume levels they have tested this but my guess would be closer to 3 hours per charge. This is a long way from the Hifiman TWS600 I reviewed recently which had 5.5 hours per charge plus another 33 hours from the case.

One last gripe about the battery is the charge times. As said, there is no quick charge, they even warn you against using a quick charger, and the IEMs take 2 hours inside their case to reach a full charge (so, 2 hours charging for 3 hours of playback) and the case takes 2 hours to charge also. I feel that quick charge, at least for the IEMs, would have been a huge improvement.

As far as connectivity, they use the AAC codec which is not exactly a highly regarded codec, without and Aptx HD or LDAC. They do use Bluetooth 5.0, which should improve connectivity but I have had a few dropouts and the range is not very good. They claim 20 metres although my experience has been more like 12 and there is no hope of leaving the room your device is in, which after being spoiled by the connectivity of the TWS600, is pretty poor.

The dropouts I mention are not regular but now and again they do suffer from a few weird moments, like the left channel dropping out or them refusing to connect. A quick disconnect and reconnect fixes the issue but it can still be a bit of a pain, especially if you are in the middle of doing something else. There are also instructions in the manual on how to reset the IEMs if you have any issues.

For control, KZ have opted for touch control rather than a physical button, with one tap to play/pause, two taps for next/last track, a 2 second press for activating the assistant and a triple tap to activate what they call “high performance mode” (more on that later). The touch works pretty well, with most of my taps being recognized, as long as the taps aren’t too quick. If you do a quick double tap for next track, it usually only recognizes a single tap and pauses the music. It is also worth noting that there is no volume control capability from the IEMs, so this has to be done on the source device. It is not the end of the world but I would much prefer to be able to increase or lower volume direct from the IEMs themselves.


Please note that all of my impressions regarding sound have been made using the silicone tips. I did try using foam tips (which are usually my preference) but it dropped the overall volume by quite a bit. I played around a bit to see if I could fix the seal issue but due to the shape of the nozzle, it seems to open the foam tips I have too much and I can’t get a correct seal.

The KZ S2 have a very V shaped signature, with an emphasis on bass and treble but with a dip in treble that removes a lot of air. To be honest, the sound signature of them I would class as being fun. I don’t think that they should be considered as reference for anything (nor do they say they are) and should be looked at as an IEM that is for enjoyment rather than detailed listening of music.

In the bass category, there is plenty. In fact, I have not found a single song where I thought it needed more bass, where I have found plenty of songs that had too much. The bass extends pretty low, getting down into sub bass category, and the higher end of the bass rolls over into the lower mids, not so much as a bleed more as an invasion. That is partly due to the recessed mids but also due to the excessive amount of bass at times.

Working through my normal playlist, I found songs like “Royals” by Lorde or “Way Down Deep” by Jennifer Warnes, I found the bass to be excessive and to literally drown out a lot of the rest of the spectrum. On a song with a huge amount of bass, such as “Bury A Friend” by Billie Eilish, it is a wall of uncontrolled bass, but then again, so is the actual song itself.

On songs where the bass guitar is recorded at a more balanced leve, such as “Smooth Operator” or “No Ordinary Love” by Sade, the bass actually has a nice warmth to it and seems to keep itself more under control, although it still overshadows Sade’s voice which could do with being a little more present.

The intro to “Elephants On Ice Skates” by Brian Blomberg is slap bass which actually sounds pretty good until the “real” bass notes kick in, they then overshadow the slap line and make it seem like there are two different basses, one artificial and the other a bass guitar.

Where the bass did perform really well was with instrumental EDM, and even some 80’s Electro, where the bass felt huge and smooth, giving the impression of listening to the tracks on something much bigger than these tiny IEMs.

Moving to the mids, these are recessed, excessively in my opinion. I have nothing against V shaped signatures when listening for fun, but in the case of the S2, I certainly think the dip after the bass is too much. On the instrumental EDM I mentioned, this is not actually an issue, but music that depends on vocals suffer. I mentioned this above with the two Sade tracks, where her voice could certainly use some more presence, but I also found it to be true in many other tracks.

“No One” (the acoustic version) by Alicia Keys is another example, “Hotel California” by the Eagles is another, most of the Dr.Dre tracks I listened to also suffered, and the list could go on.

Reaching up into the treble, the treble is back to being more present than the mids (which is not exactly difficult) but it seems to drop of pretty quickly, which removes some of the airyness that it could have to counteract the bass heaviness.

There also seems to be a dip in the treble tuning that works pretty well to avoid sibilance to some extent. Not all tracks are sibilance free but they are not overly exaggerated like on other offerings (some of which are from KZ themselves). They certainly can’t be considered bright.

In songs that I usually find plenty of sibilance in other, brighter, IEMs, such as “Hope Is a Dangerous Thing” by Lana Del Rey or “Sugar” by Francesco Yates (the acoustic version), the treble is pretty well contained. However, in “The Expert” by Yello and “Rockabye” by The Mayries, it is a little more noticeable but still not enough to be painful (just a little irritating at times).

As far as soundstage and imaging, they are nothing to write home about. Most IEMs (at least in this price range) are not very wide but I would say that the S2 are even less than normal. You still get a good stereo presentation but it is very close. The imaging is also not great, I mean, it is not terrible but as the presentation is pretty narrow, in songs like “Letter” by Yosi  Horikawa, there really isn’t anywhere for the pencil to go.

While on the subject of stereo imaging, I have found something that has struck me on some songs. I sometimes get the sensation that the right channel is ever so slightly ahead of the left channel, causing a fake sensation of reverb on songs that already play with this effect in the recording. It can also sometimes make me feel as though the voices are slightly focused towards the right channel, due to that channel leading. It is difficult to explain and is not always noticeable but it is the equivalent of panning two identical voice tracks to the left and right in a recording and then nudgin the right track a couple of hundred milliseconds in front of the left.

With regards to timbre, I have mixed feelings. Whilst in the lower registries everything seems to be pretty natural (if we ignore the bass boost), in the upper registries some instruments present a slightly metallic sound to them. This was noticeable in songs like “Jack of Speed” by Steely Dan or “No One” by Alicia Keys, where the snares and guitars presented a metallic shine to them in the higher registries.


I want to mention video briefly as the “high performance mode” that is accessed by a triple tap is actually aimed at video consumption. When you turn this mode on it cuts the latency of the IEMs to a point where it is virtually impossible to claim you can see any sync issues of audio vs video. I used these for watching some series and movies on Prime and was pretty impressed by the response.

The recess in mids is not the greatest for making out voices when there are explosions and stuff going on around them, but I feel that the sound quality for video consumption is on a par with the majority of basic 2.1 setups that a lot of people have at home hooked up to their PC (in other words, normal people that aren’t focused on SQ ;) )

This mode does reduce the battery duration though, so you would need a backup if you wanted to watch Lord Of The Rings.


As I mentioned in my review of the Hifiman TWS600, it seems my phone has issues with bluetooth headsets so I couldn’t really test them much. A few calls that I did make, the other side complained that the quality wasn’t great and I ended up switching over to my Koss PortaPro which are my “go to” for most calls.


The KZ S2 has a list of things that could be classed as faults until we put it into perspective, they are a true wireless IEM that cost 20€ (at least when I purchased them) and they do a job that is more than adequate for that price.

The connectivity is not the greatest, the sound signature is overly bassy and lacking in mids with a bit of a metallic ring in the highs, however, they are not an IEM that I hate. In fact, I can think of plenty of occasions when I would be in the mood for them.

If you like plenty of bass and enjoy EDM etc. I think that you would probably enjoy the S2. In fact, if you are not going to sit and analyze the sound, I think you would probably enjoy them when you are listening to music while doing other things, making the most of the TWS commodity. They are IPX5 rated so they are a decent option for the gym and would certainly provide plenty of that bass that so many people enjoy while training.

For video, they are also acceptable with the “high performance mode” on. The sound signature is not the greatest for movies and series but is acceptable.

I would say that the KZ S2, although they are not the greatest in sound quality, are a pretty decent set of TWS IEMs to just throw in a bag to have handy at all times, at least at the price I paid. If they cost double then I think I might try some other models before picking these.

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