Review - Kiwi Ears Allegro

Review - KZ ZST X (sub 50€)

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Also available on YouTube in Spanish: Acho Reviews YouTube 

The KZ ZST X are another update of an older model by KZ. Over the past year or so, KZ has released many of their models in the X form, sporting upgrades to models from yesteryear, or in the case of KZ, yestermonth.

I had the original KZ ZST some time ago but to be totally honest, I can’t remember much about them, therefore I am not going to be making comparisons to the originals in this review. However, at the price point of around 15€, there are various competitors in the same price bracket, some of which are by KZ themselves.


The ZST X arrives in the typical KZ white box, with an image of the IEMs on the front and some specifications on the back. Inside the box is the usual foam insert containing the IEMs, underneath which we find two extra sets of KZ starred silicone tips, a user manual and the usual KZ 2 pin cable.

In my case, I also received an extra plastic bag containing some foam tips, all in the same size but in 4 different colours. This was packed outside the actual KZ box so I am not sure if they are shipped with all ZST X IEMs or just from the seller I chose.

Build and aesthetics…

In my case the IEMs are green but other than that, it is the usual KZ transparent plastic shell. No changes in shape from so many of their other IEMs, very lightweight and sporting the usual KZ two pin connector.

ZST X is written across the IEM in a way that resembles graffitti and in the case of this model, the phrase of choice that KZ has written on the IEMs is “Upgraded Sound Quality”.

Really there is nothing special about these that differentiates them from so many other KZ offerings and if you find one set of KZ (that uses this shape) comfortable, you will find them all comfortable.


Here is where we should be looking for something interesting, as KZ themselves say they are “Upgraded Sound Quality”. 

If I remember correctly, the original ZST was the first hybrid from KZ, something that led to many many more hybrids from the company, seemingly each time with more and more drivers. In the case of the ZST X, it is again a hybrid but is a simple 1x DD plus 1x BA driver. I believe that the original was also a 1+1, so it must be the quality of the drivers, or the tuning, that they have upgraded.

Just before I continue, let me mention that I have been using these with Xelastec tips as they are my preference for tips at the moment and they did not affect the sound in a negative way in comparison to other options.

Starting with the sub-bass, there is quite an extension down to the lowest frequencies and although these IEMs do have a V shaped tuning to them, the lowest frequencies are not as boosted as many other V shaped IEMs at the cheap end of the market. 

The bass is also not of a great quality, and while it is not overly boosted, it ends up feeling quite bloated and out of control at times, this holding true for the entire low end of the ZST X. Songs like “No Sanctuary Here” do not sound clean in the low areas, making the song much less enjoyable.

Unfortunately the lack of cleanliness also rolls over into the lower mids, resulting in the low end of acoustic guitars sounding less than natural. Listening to songs like “Seven Nation Army” by Zella Day, the low end of the guitar seems disconnected from the remaining frequencies, as though it is in the background.

The mids are not bad through the center of the frequencies but as soon as we start hitting the higher mids, it seems that these come across a little harsher than I would like. Voices like Becca Adams in “Pretty Girl” do not sound very natural, with an over emphasis in the higher regions of her voice, lacking clarity in those ranges. Moving to songs like “Don’t You Worry Child” by Beth, whose voice can already come across as harsh on many IEMs, the harshness is very present and makes her voice, and many others, sound fragile.

Moving further up, sibilance is not avoided and makes its presence known on many songs, not just my typical sibilance test tracks. Approaching the top end, there isn’t as much of a roll off as with a single dynamic driver, however, the BA driver does not present a very natural or present sound, coming across as fragile again.

The details presented by the ZST X are a bit of a mixed bag. On one hand, some of the details such as reverb and background images are presented better than I expected, however, some of the foreground details seem to be missing, or at least are not clean. It is a rather weird sensation, being able to notice the decay of a note clearly but the actual note not sounding clear itself.

As far as soundstage and imaging, nothing special to report really. The width is the general width found in most of the IEMs in the budget regions with image placement that is not great but does give you a general feel for placement of instruments.


The ZST X is a set of IEMs that is nothing special and while it would have been a great option for 15€ a year or so ago, now it is against a lot of competition in a similar price range, some of them from KZ themselves. Just to mention a few competitors in a similar price range (at the time of writing this review) I have already reviewed and how the stand against them, we have (click on any model to see the complete review of it):

KZ DQ6 (20€) - A decent set of IEMs from KZ that uses 3x DD and performs very well for the price, which is only 5€ more than the ZST X and is well worth it.

Blon BL-01 (15€) - These don’t really have anything wrong with them in the sound sector. They do have a fixed cable and aren’t really that comfortable (to me) but I still feel they are a better buy than the ZST X at the same price.

KBEAR Lark (20€) - I really wasn’t a fan of the Lark, finding lots of problems in the higher regions but there are supposedly two versions (I got the bad one) and the other one is praised by many.

Tin T1 Plus (20€) - Nice mid range with a non-offensive tuning although details are not their strong point.

KZ EDX (5€) - The ultra-budget king! This is probably the best bang for buck IEM I have ever tried. It is not amazing but it is 5€, also made by KZ, and sounds just as good (if not better) than the ZST X.

KZ ZSN Pro X (15€) - Ok, these were certainly not my favourite set of IEMs but they are also made by KZ, they are the same price, look better (in my opinion) and while I wouldn’t recommend them, I wouldn’t say they are worse than those reviewed today.

Tianderenhe TD02 (15€) - These were the last IEMs I reviewed before the ZST X and while they are by no means perfect, I would choose them way before the ZST X.

I could probably go on with other options but I think you already get the point I am trying to make. While the ZST X are not a terrible set of IEMs for their price, they are by no means anything special and I feel that they have more flaws than many of their competitors, even those from inside their own company.

I don’t think someone looking to spend 15€ on a set of IEMs will find the ZST X offensive but there are many other options out there for the same price.

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