Jeez, I am embarassed to admit that I never worked up an EQ curve on the HD280 before I gave them away. Mind you, I gave them to my brother because I thought they sound pretty damned good out of any source. Mine also had amazing bass response. Why don't yours? Possibilities:
1) They require a damned near perfect seal. Any little gap in the pads and bass will vanish. Obviously glasses are a problem, at least until the pads take a set. Long hair will certainly cause a problem.
2) Break-in may be important. Mine were in perfect physical condition, but I bought them used. No idea how many hours of what type of music were on them, but it could be a factor.
3) Product variation. Maybe they are all different, and I (or rather, my brother) got lucky. This one bothers me a lot, actually.
4) Personal taste/calibration. My HD280s had so much bass that complaints really surprise me. Ask anybody here, I am a bass junkie! Either these cans vary like crazy, or the complaints are from people who think the DT770 has flat response. This is not an insult, just an acknowledgement that some listeners are used to a more pronounced bass presentation. In this case, nothing else will even come close, so give up and embrace the DT770 Thudmeister.
Did I miss any scenarios? I guess that driving electronics could be a factor, but the HD280 are pretty easy to drive.
gerG