[JohanK]

And there seems to be a few interestings things to note. The DT880 looks to just indeed be tweaked, from what I can recall of the old graph are there no really big deviations from the previous one. Perhaps the treble peak is slightly tamer. It should definitely be brighter than the K701, which hardly conflicts with the consensus here. As the deviations in the frequence response are farily minor, the question is if they managed to change anything else when they tweaked the sound and, and if then, what. To get an idea of that, I guess I have to go back to the old comparation threads and look through them.

I do not know about the DT770, but the new DT990 seems to be a tweaked more towards a neutral but fun sound as opposed to just being fun. The previous one had a significantly more smile shaped response from what I can recall. The new one looks like a DT880 but with more bass.