I bought these earphones (or rather IEMs) in July of last year, and since then I’ve bought another pair of headphones that costs over 7x. But I still think this is a good pair of IEMs.
They cost me ₹1800 in India, and they cost around $20 in most other countries. For the price, what you’re getting is good sound performance and acceptable build quality. These IEMs sound better than your regular Sony or JBL earphones, or any other popular brand in this price bracket. The soundstage is quite decent. In fact I was surprised by it the first time I tried these on, and I’m still occasionally surprised by it on some songs. It’s not a large or accurate soundstage by any means, but it’s better than your $20 Sony earphones that have no sense of space and sound in-your-head.
The tuning is V-shaped – far from the Harman target – so you get a sound signature that is bright and bassy. They sound shouty sometimes and there’s sibilance, but it’s fine. These are $20 earphones after all. The imaging and separation is quite good – much better than the $20 offerings from other brands – which is why these are a much wiser choice any day. Most $20 earphones from popular brands just sound bassy (not even good bass, just muddy bass), and lack severely in imaging, instrument separation, and soundstage.
What I’m trying to convey here is that Chi-Fi is almost always a better choice than well-known brands in this price bracket. The KZ ZST may not be the best $20 earphones out there, but they’re definitely better than your traditional $20 pair from a big-name brand. Even though I have much better headphones now that are open-back, that have huge planar-magnetic drivers a close-to-Harman-neutral sound signature, these IEMs are not at all bad to listen to. Listening to music can still be fun and even pleasantly surprising at times, because they get so many of the basics right – imaging, separation, and a decent soundstage – whereas other earphones in this price bracket completely lack in these areas.
If you can spend a bit more money, I would urge you to skip these and get the Tin Hifi T2 Plus. The T2 Plus have a better, closer-to-neutral tuning that’s generally more pleasant to listen to. But if you’re really tight on your budget, the KZ ZST isn’t a bad choice at all. Especially if all you want is to get a taste of what a good-sounding pair of earphones, umm, sounds like. If you want more alternatives, Crinacle’s IEM ranking list is an excellent resource to see what options are available and find what you’re looking for.