Just received my ASX today. First impression is ...interesting. Build quality is okay not as good as ZAX, closer to CA16 with those noticeable seam on the clear body. Whereas ZAX, ZS10 pro, C12, etc don't have that. The silicone tip is okay, but I like KZ starline tip better and the nozzle is smaller than ZAX. This new silicone tips make the IEM sit deeper inside the ear canal thus making the isolation/fit similar to a custom mold IEM.
On to the sound, now this is the interesting part. The vocal is very middle centric, meaning if you ever heard a 5.1CH surround sound system, the vocal/dialog comes on the center channel speaker, now the ASX is kind of sound like that. Voice is very inside your head like it seriously feels coming from the middle of the brain. This can create a somewhat busy sound because the vocal is really cramped inside the head, even I have to adjust a little bit. It can be overwhelming when first listening to it. Usually, if I put ZSX and ZAX on each side, the sound will be quite similar, it might sound a little bit different like more airy on the ZAX, etc, but when I put the ASX and ZAX together, they sound totally different.
This ASX is very very detailed IEM. I said the ZAX is quite detailed, but ASX is even more detailed. Like I can hear the compression on the snare drum which usually washed out in the mix and all the little nuances too.
Treble is good, but the ZAX is more airy where ASX is more like the ZSX. Vocal has this warmth but not thick, male voice has some weight to it. Definitely warmer than the ZAX. There is a spike in the upper mid where it can exaggerate snare beat sound.
Bass hits hard, deep and fast. I am quite impressed by the bass from this new BA, it rumbles just like a DD, but it is very punchy/clicky too. No bass bleed fortunately. In term of quantity, the ASX sounds bassier than the ZAX.
Sound separation is very good, but they are different than ZAX. Its like vocal has its own space and the instruments just filling in the surrounding space.
This is just my initial listening observation tho so it can changed for the better or worse. For now, this ASX is very very interesting because it is totally different than the ZAX. I am not talking about the curve (I think it is closer to W instead of V), but the sound presentation as a whole is totally different than any other KZ/CCA I've heard so far.