However, it is not comfortable enough, even after I stretched its band span from 5" to 6.5". After some exam in a mirror, I found the problem. The joints have very little freedom; so the ear pads never settle down evenly around my ears. This video explains it well:
The fix is also shown in the video.
For those who want to open the cases to see what's inside: there are five screws under the seal, use a small magnet to locate them. The speakers are not closed type, there are large holes on the back. This may explain why this BT cannot isolate noise as well as other true closed type cans such as the RS160. Furthermore, there are large holes on the front panel, allowing even more noise in. This is also the main reason for its exceptional good sound, especially as a "closed" type, because it is more like open type, and, with phase-reverse holes like home speakers!
A small square foam was at the wrong location, it did not seat the joint, I moved it to the right place - bottom center of the circuit board. Without this soft seat in place, the joint makes click noise with the plastic case. The wire to the leather strip was too short, I removed the yellow hot glue and pulled more wire out of the case. The antenna, the small white bar on the top, is very short, I might solder a 30mm wire to it to extend the range even further, but I found that the bottleneck is my other devices (Samsung Note 2 and Sony TX/RX).
The battery is on the right side, quite large indeed, no wonder it can last for more than 18 hours per charge. With such long play time - more than a whole day, lacking of audio during charging is not a big deal. I just need to remember to plug it every night before I sleep and my music won't stop for the next full day. To less the pain further: full charge takes less than 2 hours, not the usual 3.5. When battery is low, sound becomes obviously worse. For the best sound, you really should charge it after about 12 hours, even though it can play much longer than that.
Anyone can explain why these yellow hot glue on the back of the speakers? Seems they block some holes and leave only three (or one, on the metal cover) of them open. The audio engineer seems know what he's doing, the mechanical and electronic engineers don't. I guess you can open or block more holes to tweak the sound style to your like.
I could not find its manual online; so I scanned it for you: HarKar-BT manual, in English and Chinese. The most interesting info is how to know whether it's in APT-X, AAC or A2DP mode based on the flashing pattern of the LED. There is also a flyer on the specs and features, here.
Abstract in Chinese