Build and design: I really like it. They are solid, and very well made, pretty much just as good as the $1,000 acrylic IEMs that I’ve tried. They seem like they are durable, and should serve well for several years to come. I like the shape more than the ZS10 Pro, in that they sit in my ear better, and seem more stable overall. The isolation seems slightly better. I find them really comfortable, but those with smaller ears may not like the fit as much, and the ZS10 Pro may fit better. It comes with the usual KZ brown cable, which I don’t mind, but many do. The cable does tangle easily.
Sound: Overall, I would say it has a mild V-shaped sound. The mids are a little recessed, but only slightly, and are quite well balanced with the bass and treble. The bass is pretty fast, but with the rich DD sound. There is good punch, and a bunch of sub-bass, plenty enough for bass heads. The mid-bass is just the right amount, and doesn’t muddy up the lower mids. The midrange sounds smooth and clear. There is good texture, but with the typical BA timbre. Vocals sound nice, not forward at all, but also not drowned out. The mids sound detailed, but nothing spectacular. The treble is very crisp, clear, revealing, and airy, without sounding harsh or sibilant. It is just right.
Compared to the ZS10 Pro: The impedance and sensitivity ratings of both IEMS are identical, and do sound equally loud at the same volume settings. The bass on the ZSX sounds slightly faster and clearer, with a little less quantity. The sub-bass balance vs the mid-bass sounds the same. The mids are a little less recessed, and are more revealing on the ZSX, and the treble is more airy and detailed. The ZSX is better, and more balanced than the ZS10 Pro, but the differences are quite small. Between the 2, I would choose the ZSX. If you already own the ZS10 Pro, enjoy it, and I recommend using any additional cash on something with a different sound signature such as the Tin Audio T2, which is much more neutral sounding, or maybe the TFZ S2 Pro, which is warmer, with less sub-bass, and less airy treble, but with the alluring analog sound of a single DD.
Conclusion: The KZ ZSX is an excellent budget IEM, that doesn’t sound like a budget item. I can imagine many consumers purchasing these and not feeling the need to upgrade any more.
Would recommend to a friend.