Ok ... so I received the ZAX in the mail today. After an afternoon of listening my initial impression is that these are stupid good for 45 euros
I can see why people are in love with the similar CKX that has a touch darker treble. I will be ordering the CKX because I think both sets are destined to be classics, and I think my wife would love them as well, especially with her smaller ears. I can't believe it's taken me so long to catch up to last year, but here I am.
I was happy to see a full compliment of starlines in ZAX box, and the pretty silver plated cable with clear plastic touches is a nice improvement over KZs famous brown jobber. Along with the starline tips I'm using the copper cable from the C12s to burn them in and they are a touch dark. I found another online review (outside the head-fi fam) who claimed to prefer lots of treble and thought his set were dark, too, so I don't think I'm crazy. I'll try the silver plated cable tomorrow as opinions and burn in have only just begun.
Any and all bass issues my C12 had on fast metal are gone OOTB. The double magnet thing seems to work, but from what I've read online about other tech I think that KZ are probably a step behind the beryllium and carbon nanotube DDs that are collecting fans among the other chifi marques. Quantitatively there is more bass (> 60hz) to my ears over the C12. I'm holding any qualitative thoughts about bass until they burn in as the C12 are quite potent here with a touch of EQ. For synthwave, trip-hop, and most jazz I've tried to date the C12 is just pitch perfect.
Subbass is too early to tell. It's not disappointing by any means, but the C12's exercised 7mm is holding its own here relative to ZAX's 10mm with no burn-in. I'm not hearing that big of a difference in electronic or synthwave music for the moment below 60hz.
I was dying to know how these fared for classical and orchestral pieces. Initial observation is that contrabass and cello strings are audibly and markedly improved right out of the box. Violin and horns are about equal in tone and timbre wise to my ears relative to the C12. I think the mid-bass and mids-to-bass transitions are better tuned over the C12. Plus, we've got 4 more drivers to play with, so no surprise here. The more problematic (busy) orchestra pieces that were tripping up the C12 get a passing grade. Still not as detailed and layered as they could be, but its passable when things get busy.
The big difference in classical works is from the enhanced soundstage, which I would deem "very good" at any price. There is definitely a much wider soundstage than the C12 can muster and this is the biggest and happiest improvement. I'd put ZAX easily on par with the bumper crop of $100-$250 studio closed-back headphones for soundstage and positioning, which is how my ears are trained after decades of use, starting with Sony V6. Open backs are a different story, obviously. When I want crazy soundstage I reach for my Grados.
Treble in jazz is close to being a wash to my ears. With the C12s, players like Miles Davis, Charlie Parker, and Stan Getz in his pre-samba days are freaking
lit. Using the same EQ presets with the ZAX reveals more width and maybe juuuuuuuuust barely a touch more of what reviewers call sparkle (12 kHz and up). I still think the C12 is a very good choice for jazz with that set being a bit more analytical, and the ZAX being a touch more musical and maybe less revealing. A paradox, I know.
My only slight disappointment is that when I ordered them I thought that the ZAX
might be a bit more open given the shell design. These provide about half the isolation of the C12 which is one of the reasons I ordered them over the CKX (another big one was reports of the increased treble, which is good for me). I need to be able to hear what's going on in the house and my office. Pausing the music is enough to have a quick conversation without removing the IEM, so that's Mission Accomplished for my personal requirements. They do leak a bit at high moderate to loud volumes. but this isn't an issue for me. In a busy office I would choose these over a more isolated pair if you have to regularly deal with interruptions.
Fit and finish: I managed to find a cyan resin shell with black faceplate and find these to be a great looking set with a premium feel that belies their asking price. The shell shape is about 95% the same as my C12, and the driver positioning internally looks very similar to the C12, too. Fit is very similar with the ZAX being overall smaller and smoother from its curved faceplate.
Based on what I've heard today I really like these but will not be ditching the C12 anytime soon. I A/B tested them by putting one each on the brown cable and mixing FLAC tracks into mono with combined L+R. The ZAX is more efficient yielding 5-10dB more volume than the C12, so I had to compensate in the balance. Moving left to right during different passages on my reference tracks didn't yield as big of a difference as I thought there would be, but switching between full sets the bump in SQ is more apparent. Maybe the moondrop aria or starfield is as good for some folks' ears as these, but I don't see them keeping up with the ZAX in resolution or soundstage. I'll never know and that's fine with me.
I will report back in a couple of weeks to see if anything's changed opinion wise. I think I'm going to target one of the EST hybrids from Mangird or Tri in a couple of months in a higher price tier rather than go down the ASX/AST rabbit hole. I canceled the CSNs; I sadly don't have enough time to devote to comparisons for comparison's sake. I will stay tuned for KZ and CCA's next releases and maybe jump on a blind purchase for one of their future ears. cheers