Review - Fosi Audio SK02

Review - QKZ x HBB

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Also available on YouTube in Spanish: Acho Reviews YouTube 

The QKZ x HBB have been sent to me by Linsoul for me to try out and share my opinions in this review. They have not requested anything specific and, as always, I will do my best to be as sincere and unbiased as possible in my review.

You can find the QKZ x HBB via Linsoul here:

The above is a non-affiliate link, as are all links that I share, meaning that Ireceive nothing in exchange for clicks or purchases made via the link.


There is no denying that HBB (Hawaiian Bad Boy) of Bad Guy Good Audio Reviews has become the king of collaborations in previous times. I really can’t keep up with the amount of models that he has helped tune in recent times, a lot of them in the budget segment. The QKZ x HBB is another of those in the budget segment, costing less than 20€ and placing itself firmly inside the sub 50€ bracket that I consider extreme budget on Acho Reviews.

I have tried a few of HBBs collaborations and I have to say that they have impressed me in general, offering a lot for very decent prices and I will say that these are another of those models. They may not be for everyone, I will get into details on my thoughts in a second, but I can confirm that, without even getting into the review, yes, these are more than worth the asking price. Is the tuning going to be to your preference, well, I guess that is something that I can use as an excuse for you to read the review. But if you want a TLDR… if you want a 20€ stocking stuffer (with the holiday seasons approaching), then you can do a lot worse than these IEMs.


When we are talking about a set or earphones that cost not much more than a meal at McDonalds and we want them to sound good, there has to be something cut somewhere. What better place to cut it than in the packaging and accessories section?

In a plain small box that is overloaded with info on the exterior, we get the IEMs, a cable with inline microphone and 6 sets of silicone tips. It is an unboxing experience that is very reminiscent of KZ (or other budget QKZ models) but is more than adequate for a budget model.

Yes, the presentation is very basic and cheap, but there are models that cost triple this amount with similar presentations and, again, I would rather the costs be cut here than in the IEMs.

Build and aesthetics…

The IEMs use a generic shape that is comfortable for most people, with translucid shells and a face plate that sports the HBB logo on one IEM and the QKZ logo on the other. The logo is behind a perspex window that gives depth to the aesthetics, with grey lightening bolts on a black background behind. Surrounding the faceplate there is a metal coloured frame that gives some more “boost” to the aesthetics.

These IEMs are not something that aims to look boutique in their aesthetics but at the same time have their own original design that is nice to see.

The cable is also very reminiscent of the cables included by KZ. I don’t want to say that it’s identical but… it seems to be. The inline microphone works for the odd phone call and for talking to your assistant but is not something that you will be recording your latest single with.

In general, these are a 20€ set of IEMs and I have to say that the build and aesthetics are more than worthy of their price (or more).


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

I am going to be sincere and straight to the point here, I am not a fan of the sound of these IEMs. I know that I said just a moment ago that these IEMs are well worth their price and that you could go out and buy them even without reading the review, and I stick by what I said. They are a good set of IEMs for their price but… cinnamon is a good ingredient but it doesn’t mean that I personally like the flavour.

If you have followed any of my reviews, you know by now that I am not a huge fan of overly present bass, especially midbass. Yes, there are sets with overly present midbass that I enjoy, for certain genres and at certain times, and I have enjoyed these for some stuff. However, overly present midbass does cause me fatigue over longer listening periods and the QKZ x HBB are one of those sets.

Now, I am still not going to complain about these IEMs as I think they will be a great buy for those who do like more in the bass, I especially found these a lot of fun for EDM. But before I get into describing each of the sound sections that I usually do, lets take a look at the graph in comparison to my personal preference target:

In the subbass, we have plenty, giving us enough rumble (in my opinion) for even the extreme bass heads amongst us. My usual subbass test with “Chameleon” I found to be overpowering… and then the bass kicked in 😁

Now the biggest problem, for me personally, is that there is one big ramp from 500Hz down. That means that everything is boosted in the low end, from Subbass to almost the center of the mids. This is a sensation that I personally do not like yet I do know plenty of people that do. Listening to “No Sanctuary Here”, this was enough to give me fatigue but it is one of those experiences that is very impressive for those that like the bass to move them. 

I went through quite a large selection of EDM and it was like being in a night club on a Saturday night, the party is great but my ears (and head) start feeling it after a while.

To my surprise, the mid range does not seem to be recessed or absent, something that I would have expected with such a large presence in the lower frequencies. Yes things like “Don’t Start Now” by Dua Lipa are clean with no lack of presence in vocals.

Even “Make Noise” by Busta Rhymes and Lenny Kravitz did not place vocals any further back than usual. This track is already pretty weird in its recording, with Busta’s vocals taking a back seat to the backing vocals and the instrumental, but on some V shaped sets his vocals disappear almost completely, and that wasn’t the case here.

I would have also expected the upper mids to need more boost that they have in order to counteract that low end but, again, I was surprised to find that they are actually quite clear and respectable. I really didn’t find that things were struggling to fight for their place in the music, they were upfront and clear enough.

The treble extension is also not back, not the smoothest of trebles but acceptable. It has a few peaks here and there but it is not something that I think will offend many people who are looking at this kind of signature at this kind of price.

Soundstage is around average I guess, nothing spectacular going on, and I would say that image placement is about the same. Things are place well enough but they are not milimetric, not that I think that is something that should be a factor in such a tuned IEM.

Details are not great but those upper high range peaks do help give them more of a sense of detail (even if they are not that detailed), something that I think will be appreciated by many who enjoy EDM.

Isolation is also about average but one thing I will say is that you are not going to have any issues hearing the bass. If you are listening to anything with a good bass presence and at a level that is common for many EDM fans, then you will not need to worry about external noise 😉


I know this is going to come across as a very strange review. On one hand I say I don’t like the QKZ x HBB, yet on the other hand, I say that they are worth buying without a doubt. And they are.

The thing is, these IEMs, due to their tuning, give me a headache and cause me fatigue. However… I am not you. There are millions of people out there that have tastes very different to mine and I know a lot of people like sets with very present bass. And I would say that at 20€, these give a lot for their price. 

There is a lot of competition out there lately in this price range, with me preferring a lot of other models over these, yet I cannot deny that if you are looking for a bassy set of IEMs on a very low budget, the QKZx HBB have a lot to offer. 

All FR measurements of IEMs can be viewed and compared on
All isolation measurements of IEMs can be found on

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