@Makafuni
I hope the Hifiman QC team didn't mess up with the polarity of the drivers here in his pair.
Why does it seem to me that one of the drivers may actually be wired in reverse?
@odyo
Try this
phase test: the first one (in phase) should be a normal bass drop, DEAD CENTER. It should be the exact same in both ears, no difference should be there.
The second bass drop (out of phase) should be outside (it's with reversed polarity), like a soundstage chorus, hard panned left and right, and nothing in the center.
If it's anything but these, there's a wiring problem or a driver problem or both.