Review - Fosi Audio SK02

Review - Letshuoer DZ4

English | Español

TLDR version on YouTube: TDLR - Letshuoer DZ4

The Letshuoer DZ4 has been sent to me directly by Letshuoer in exchange for me to try it out and share my impressions in this review. Letshuoer have not made any requests or comments and I will do my best to be as unbiased as humanly possible.

You can find the official page for the DZ4 here: https://letshuoer.net/products/letshuoer-dz4-triple-dynamic-drivers-single-passive-radiator-edc-hifi-in-ear-monitor

As always, this is a non-affiliate link.

To avoid being repetetive in my reviews, you can find all the info about how I create the reviews, equipment used, how I receive the products and how to interpret my reviews by visiting: About my reviews


Intro…

I first heard the DZ4 back in Munich, or at least I think I did, as my current impressions are slightly different to what I remember. This could be due to the fact that I listened to a lot of stuff in Munich and have listened to a lot more since, but I just remember the set being darker when I listened to it back then.

That is not to say that the DZ4 that I have is bright, I will get to my sonic impressions soon, just that it doesn’t seem to be as dark as I remember.

The DZ4 is a set that features 3x 6mm Titanium Dome Dynamic Drivers, along with a 6mm passive radiator. The addition of a passive radiator is an interesting concept, yet it seems to be implemented in a way that is different to what I would expect for a passive radiator. While I do not proclaim to be an engineer, far from it, I have had experience with the implementation of passive radiators in speakers and subwoofers in the past. I even put one together myself for a bass cabinet some time ago, after a lot of trial and error in WinDSD.

Without getting too far into the science behind it, let me briefly mention what a passive radiator is. It is basically a speaker that does not have a voice coil or magnets etc. and does not produce any sound on its own. In other words, you don’t connect cables or an amplifier to it as it is sort of a dummy speaker. This is used, at least in my experience and understanding, instead of a port in a speaker (the hole that lets air in an out) and allows more response in the bass ranges in comparison to a simple sealed cabinet design, although with a steeper roll off. There are obviously a lot more scientific things going on behind this simple explanation but I wanted to just share the basics. 

Why am I saying this? Well, in the case of the DZ4, the passive radiator is not actually in a sealed enclosure (the IEMs are semi open), meaning that the way it is implemented is different to what I have learned about the implementation and functionality of this set up. While I can’t say exactly what the passive radiator is responsible for in the case of the DZ4, it would need to be compared to the same IEMs without the radiator, I will say that there doesn’t seem to be an extra boost in the bass and the roll off is not really steeper, in fact, if anything, it is less than on a lot of other dynamic driver sets.

Anyway, enough rambling on about what should and shouldn’t happen, let’s get on with reality and what my experiences have been with the DZ4.


Presentation…

The packaging and contents of the DZ4 are very respectable for a set of IEMs that cost around 80€. The external packaging is a simple white but elegant box, covered by a white sleeve that has some modern looking designs on it and basic info about the set.

Opening the box we find some paperwork under which the IEMs are sitting in their respective foam cutouts at the top, with a large round storage case below. I say storage case because it is rather large to carry in a pocket (although you can obviously transport the IEMs in it). The case is made of a plastic with a satin finish to it, which feels quite nice. The top screws off which is a nice touch but also takes many turns to open, which is not really a complaint but does mean it takes a little longer to open.

Inside the case we receive the cable, which is a very nice cable at that, along with a circular disc that holds 5 sets of tips, plus the ones installed on the IEMs themselves. The tips are labelled as “Vocal” and “Balanced”, 3 sizes of each. Personally I found I preferred the “Balanced”, as the “Vocals” tend to give a little extra harshness to the upper mids, something I find works against the sound presentation that the DZ4 are going for.


Build and Aesthetics…

The IEMs use a shell that looks like plastic, although it is shown by Letshuoer as being anodized aluminum. The shells are a creamy colour with a bit of a pink hue to them, with a metal face plate which has an aluminum finish to it, also with a hint of pink (matching the hardware of the cable). The face plate features a Z shape cutout with a red grille behind it and I have to say that I am a fan of the aesthetics. They look original and are not too “loud” about being different.

The nozzles are rather large but not large enough to cause any issues, at least for me, and in general I find the IEMs to be nice and comfortable. I spent some long sessions with these IEMs and found no issues with comfort at all but, as always, everyones ears are different.

The cable is reminiscent of the cable I received with the S12, although a little thinner and less bulky, something that I prefer. The IEMs use a normal 2 pin connection and in this case, the cable is terminated in a 3.5mm unbalanced connector. While some will miss the balanced option (which is easy to swap to), I have actually found that, when testing with a balanced cable, I didn’t really find the results to be an improvement over the unbalanced. In fact, as with the “Vocal” tips, the small change moving to balanced I think, again, works against the vibe of these IEMs.

In general they are well built, look good and are comfortable IEMs (all to me personally of course).


Sound…

All tracks mentioned are clickable links that allow you to open the reference track in the streaming service of your choice (YouTube, Tidal, Qobuz, Spotify, etc.)

Let me start off by saying that these IEMs have a vibe to them that I like but in certain contexts. 

I have said many times that a lot of the music I listen to is simple vocal centric music with simple acoustic instruments and I find that the DZ4 give a special flavour to this. These are not the most detailed of IEMs, I don’t find myself focusing on string attack of guitars nor on minute details happening in the percussion section. I find them more relaxed, smooth, with a habit of making simple things sound a little fuller and more “rounded”. They sort of have a warm sound to them when reproducing simple stringed instruments but without the additional presence of bass.

Let’s take a look at the graph in comparison to my usual preference target as a reference:

You can easily see that they are close to my target and that is something that obviously puts them off to a good start for me personally. However, while I have no disagreement with the tuning, nor do I doubt it is very close to my preference target, I do find that the presentation is very different to the usual more clean and neutral response that the majority of IEMs tuned in this way present.

It is difficult to explain with words but to use a reference that I have used sometimes in the past, it is a similar presentation to a set of Sony speakers that I have had for many years. They (the speakers) are not the most detailed nor impressive of presentations, yet they have a relaxed way of making things seem warm and smooth (again, without additional bass presence). It is similar in some ways to that extra vibrance that a tube amplifier adds, where the frequency response may remain the same but the sensation is of more body.

This is something, as I just said, that I find works very well for my usual preference in music. Adding flavour and intimacy but without losing soundstage or presence. In this regard I have enjoyed the DZ4 very much.

However, moving over to my usual detailed listening session and focusing on my list of test tracks (available here as always), these things that are beneficial to certain music I find to be detrimental to others. They can actually make the lower end sound thin and almost as if phase cancellation is occurring. So, to keep things consistent with all my reviews, here is what I experience when putting them through my usual tests.

Subbass is not rolled off but I would say that, for those looking for a bass head presence, these are not going to fit the bill. While I don’t find the subbass to be too weak for my tastes, in fact it is over my reference on the graph, the DZ4 does not give a sensation of a huge presence in the lowest of notes. “Chameleon”, as my usual reference, is not a track that I find to be impressive on the DZ4. There is rumble but it is not the cleanest and I get the sensation of more presence due to that than due to the amount of subbass per se. I would much prefer more presence but cleaner (or the same presence but cleaner).

Midbass is something that goes the same way. As far as the quantity, I find the DZ4 to be leaner than I would have guessed looking at the graph. Again there is some body to the bass on simpler tracks, with that almost pseudo-harmonic sensation, but with “Crazy” as an example, I find the lower end of the guitar to be a little boomy but lacking in presence at the same time. This is a sensation that I have not come across before in IEMs.

Moving to something more electronic, like “No Sanctuary Here”, again I find the bass to seem to lack presence yet still be a little out of control. It is not terrible, by no means would I say that the bass is loose and boomy, but I get a similar sensation to “Crazy”, where the bass seems to fill out but not present itself in a way that impresses those looking for a great bass hit.

The mid range is something that works much better for vocals and acoustic instruments than it does for electronically produced music. With something like “Sun Is Shining”, there is again this pseudo-harmonic response that makes things seem a little unclear and thin, whereas a track like “Happens To The Heart” the vocals get a lovely smooth body to them, the same with vocals by Dominique Fils-Aimé in “Strange Fruit”.

The upper mids depend on the tips used and here is where I found the “Vocal” tips worked to bring vocals forward and provide them with a little more clarity, for example “Whole Lotta Love”, whereas the “Balanced” tips sort of merge the vocals into the lows and mids on that track. While I would say that bringing vocals a step forwards may be beneficial, as I said before, it seems to work against the overall presentation of the DZ4. I find that when vocals are brought forwards, it makes them stand out against that smooth bodied signature, making them seem harsher than they actually are.

As we get into the upper ranges, the treble is quite tame and again smooth but with a slightly “off” sounding timbre. There is no sibilance, both “Code Cool” and “Diamonds On The Soles Of Her Shoes” are tamed in this regard, yet I do find that the upper ranges of pianos can come across a little unnatural. This is mainly because, in my opinion of course, the upper ranges don’t seem to have that same pseudo-harmonic sensation that the lower ranges do. This means that when instruments that extend well into the higher ranges, such as the piano, have a tonality that is slightly different to the tonality of the same instrument in the lower ranges. I don’t think that this is because the treble is actually wrong in it’s tonality, just that it is different (possibly more natural even) than the lower ranges, creating the sensation that something is not quite right.

Soundstage is decent. I wouldn’t say it is huge but it is above average for a set of IEMs. However, that extra body makes things sound fuller and as though there is more space around you, which, again, works very well for acoustic instruments and vocals. Detail and image placement is not great but I don’t feel that it is due to it lacking, more that it is smoothed over giving a general presentation rather than individual image placements for the smaller details.


Conclusion…

The DZ4 are a set of IEMs that I have enjoyed immensely for my day to day listening, where I found myself enjoying album after album of acoustic music from many artists. That feeling that there is a bit of tube flavour (sorry but I can’t think of a better description at this moment) going on in the lower and mid ranges is something that I find enjoyable for relaxing and enjoying the music. However, when moving over to specific more detailed listening tests with other genres, I didn’t feel that they were quite as enjoyable.

To be honest, I don’t think this is necessarily a bad thing at all. They may not be an all-round detail focused IEM but there are plenty of those already on the market, it is nice to see a different approach to the presentation of music.

I honestly think that if you are someone who mainly listens to vocal centric and acoustic stringed instruments, then the DZ4 are something that you are really going to enjoy. If your tastes lay in other genres and/or you are focused on detail retrieval, then maybe look elsewhere.

By no means is this a negative review, in fact, if I were to review these as a consumer with my tastes, I would say these are excellent. However, reviewing them from the viewpoint of a reviewer, there are things that are to be taken into consideration.


All FR measurements of IEMs can be viewed and compared on achoreviews.squig.link
 
All isolation measurements of IEMs can be found on achoreviews.squig.link/isolation

To comment or contact, visit any of the following social media platforms: