I think frequency response only tells part of the story. It gives an indication of what to expect, but not everything. For example, the Q701 has better bass depth and punch than the HD600 according to headroom's graph pictured here-
Now anyone who has heard both will know that is not the case, actually finding the opposite to be true(though the Q701 does have excellent bass extension). While it's true the HD650 is bassier, the HD600 is by no means bass light. Though, it is strange that measurements can show one thing while what one actually hears may be quite different.
I have owned DT770's, and still own K81. I have not done any A/B testing, because I haven't owned these at the same time, but from what I remember, the AKG's had louder sub-bass. Edit: no, fk me, I must have been in drugs when I wrote this.
Also, with my friend we compared his Sennheiser HD205 vs. my K81's, and we both found out that AKG's have way more bass, and sub-bass. I had to boost 10dB @32hz to get the Sennheisers anywhere near the AKG's bass level. Although my AKG's had 100hrs+ on them, and the Sennheisers were brand new. But still, can burn-in make such a big difference?
Anything wrong with my ears, the graphs or both?
Edited by Headzone - 2/18/12 at 5:34am