Tiny but damn surprising. The KZ HDS1 sound crisp on the highs, but quite mediocre on the mids. The bass is punchy but don't expect any amazing bass, or sub-bass, from these. One important point - the loudness of these earphones is insufficient, even on amplified sources.
NOTE: This model was most likely discontinued. It is very difficult to find for purchase.
The sound is surprisingly good, considering the small driver.
A nice looking tiny housing.
Extremely comfortable to wear.
The highs tend to be too bright.
The sub-bass is slighly distored at times.
The same gut-like cable KZ uses for their products.
The splitter is way lower than chest-level and makes the cable wiggly and hard to control.
Package & Accessories
Ear Tips - Single-Flange:
S+M+L, black (translucent), ?4mm bores
Build & Materials
Metal (painted), extra-small, semi-open-back, ?4mm nozzles, rigid strain reliefs
TPE, no strain reliefs
Silicone (grippy), 120cm, soft, straight
TPE, 90° angled, short, soft strain relief
Comfort & Fit
I had to use the L-size tips to get a good seal. Overall, these earphones are really comfortable, and you basically forget that they are in your ears.
Lows / Bass
Quite unbelievable bass for such tiny drivers, yet the sub-bass bare exists in these earphones, and the mid-bass isn't quite enough.
Mids / Vocals
The vocals are precise but sound muffled compared to the lows and highs, like they are being deprioritized in the highs' favor. The maximum loudness isn't sufficient.
Highs / Treble
The highs are very crisp and precise, pure enjoyment. Could be overwhelming sometimes though.