It is tough to find actually impressive Bluetooth earphones, especially in the budget market. KZ were trying to push the envelope by introducing their first hybrid Bluetooth headset - the BTE. While the BTE are definitely better than some of the other Bluetooth pairs I had the chance to take for a short spin in the past, they surely did not amaze me.
The bass is quite impressive with enough extension and depth to compete with some analogue earphones, for sure. The treble is quite emphasized and edgy, so vocals sound a bit too fierce, but also lacking a natural tonality and depth.
Overall, this is a nice attempt at Bluetooth earphones, definitely beats a lot of other Bluetooth earphones at a higher price, but there's a lot remains to improve, both in sound quality and connectivity.
Amazingly comfortable earphones, I have to say. Even without any ear loops to keep them in your ears, these housings were ergonomically designed in order to keep them holding onto your ears in a natural kind of way, without putting any kind of pressure. I could totally forget wearing them for hours. Very nice!
Pairing was hassle-free with both my PC and smartphone, and after being paired, the connection is almost instantaneous. Connection seems to be quite stable when the battery level is sufficient, but starts to lag/stutter the longer I use them, before recharging them again. Distance is OK, but nothing too impressive. Connection can be annoyingly jumpy when there's a wall in between the transmitter and the earphones. Battery life is, overall, very impressive. I could use the earphones for a few hours straight, with some standby in between. However, even before the battery is completely depleated, the earphones will gradually become unusable because of the dreadful lagging and stuttering.
Lows / Bass
Quite powerful bass, way better than I expected from a pair of Bluetooth earphones. The mid-bass is dominant with sufficient amount of sub-bass, and it more than enough even for the extreme bassheads. The bass is definitely satisfying, fun and upbeat, without introducing muddiness into the sound.
Mids / Vocals
While some of the upper-mids are emphasized and a bit edgy, the whole mids/lower-mids is quite mediocre and distant. While it's a non-issue for podcasts or simple pop or electronic music styles, it really falls short when it comes to more detailed vocal-centric tracks and complex music, like rock, metal and their derivatives. While the mids are not horrible, they do sound cheaper than expected from hybrid earphones, but still impressive for Bluetooth earphones.
Highs / Treble
The highs are on the edgy side, with obvious peaks that cause some pierce on susceptible tracks, something that is common with previous KZ models, like the ZST, ES3, and a few others. They are fierce and could cause discomfort if listened on a higher-than-normal volume, which is something you would do to have a better grasp of the mids. Level of detail is basically alright, not exceptionally detailed but also not that lacking, but the improper balancing with the mids does take its toll on the quality of treble as well, because you won't be able to appreciate them when they are constantly 'in your face'.