My take on the KZs I have (or had), in decreasing order of preference:
AS10: formidable in almost everything. I wish the shell was finished better or had different materials in order to better translate the intrinsic qualities of this all-BA IEMs. Fast snappy lively bass, great resolving mids, silky but present highs, an imaging that is somewhat in-your-face presentation but, with some concentration, it gets easy to focus. The most "different" KZ of them all, with a truly new sound signature. Not very source-demanding, but sounds better with good DAPs/AMPs.
ZS5v1: big soundstage, great presentation, gets congested easily with weaker sources but scales up incredibly well with good amps and DAPs. Great textures on the bass - it's about quality here - but has enough sub-bass to enjoy too. The mids need power to excite, and when they do, male voices come alive. Treble is best tamed with foam tips to avoid sibilance.
ZS4: snappy happy strong fun bass with a great range and reduced bleed on other frequencies. As a result, the mids, although recessed, are present and very resolving. Treble needs foam tips as it is sometimes piercing. Fit, comfort and isolation are top-notch.
ATE: it's still up here with the big brothers. The old ATE (first version) has such a personality that it is not easy to forget. It is "human" in its flaws and qualities. The female voices are rendered with the right timbre. Bass is always present, although for some tracks it gets messy. Treble is rolled off but still there, still making it's point. The "analogic" nature of the ATE is something I still value. The cable is rubbery and sticky.
ZS3: not every ZS3, but the first version, mate finish, without the foam in the nozzle, with stainless steel grilles, with copper KZ cable and with the perfect silicone large tips from Rock Zyrcon. This is the only way they will sound great, although V-shaped. Strong, thumping bass. Shy mids. In-your-face treble. Great soundstage. Great comfort. Great isolation. Some fun to carry around. Original cable is bad. They need low impedance source with lots of power. Don't even think of connecting it to the KZ BT modules. They will become turds.
IE80: the wildcard. Very well built imitations of the Senns. The bass rocker really works and raises low frequencies by some small notches when turned clockwise. Easily congested with louder music, but very "elegant" with less stressed environments. Mids are crystal clear. Original cable had inverted poles - had to buy a third-party Sennheiser-plug cable. Fit is a mess, only possible with foam tips or with shallow insertion wide silicones. I really like the IE80, but they are not for everyone.
ZST: I wish I could love them more. Never really had the chance to profit from their signature. Everytime I listened to them I had the feeling of missing something. Maybe it was because I never liked the faux-carbon printing on the shells. Maybe they never got along with my FiiO X3II. But then I painted them shells black and use them with the KZ BT cable and they are a lot of fun.
ED9: (with the golden nozzles, obviously) are great. A heavy chunk of metal, beatifully finished and with a great relaxed sound signature. Not as "magic" as the ATE, but still with that "analogic" lushness. A very good implementation of a single dynamic driver indeed.
ZS3: later version, Slater-modded to remove the foam and grille. Even with the mods - which indeed made them slightly better, they don't stand a chance to the older ZS3. More V-shaped, slightly hollow presentation.
ZSE: forward mids. Good soundstage. Easily congested treble. OK bass. Bad isolation. Cable microphonics - a lot. Nice vintage mid-80's looks though!
EDR2: well built until the back grille falls off. Great textured bass. Sticky cable. A great and fun signature and cheap enough to be a great introduction gift to those who don't know the brand. Price/performance, these rule!
EDSE: like the EDR2, almost the same sound signature but with more intrusive bass that makes them sound less defined.
ED7: (large shell) woodies goodies, with a one-note bass. They are detailed in the mids, if you can ear them... I always look at them and think about that silky wooden sound, but then I put my VJJB or DZAT and easily forget the ED7 exist. They are not bad at all, but will not get lots of use...
ATR: dull. Gave them away. Linear? No. Dull.
HDS1: very small, a problem to get them to stay in my large ears. Had to wear them upside down with cable behind the ear. Weird sound signature. Mids too upfront. Bass with low texture. Wife wears them at the gym with Sansa player. Not my favourite microdriver...
ED12: the worst of them all. Hollow annoying mids that covered the whole spectrum. Very badly built. Mine had the colour codes inverted, with red to the left and blue? (it was purple...) to the right. Shell cover was not fixed well. Had to glue it down with a dab of epoxy. Awfull experience in every aspect.
