After reading through many of the posts on this thread, and reading professional reviews. I am starting to think that the headphone manufacturers are unable to produce the same headphone twice. There are far to many people with different opinions regarding bass, treble, and mids, even when comparing to the same cans. IE: H6 vs M2, H6 vs M4U etc...
it could be a number of things, for example the size of the ears, whether or not they wear glasses ( thick frames vs thin frames)
even head shape as well, if your heads too big, maybe the headphones don't extend that far?
and of course preferences (and what their listening to prior to using those headphones) ex of say your listening to for example, the beats studio 2013 and then jump over to the h6 (the small over ear one) you'd notice a huge drop in bass, where you would almost think its anemic, when its just leaner overall. (this was what i thought when i listened to the h6, originally, but it was much more open sounding and less congested compared to the studio 2013.
theres probably more reasons, but their just not coming to me atm
Also