the 770's have a much clearer sub-bass/bass signature with a slightly less clear mid range and high range

I am partial to the Senn 4.50 NON-noise canceling, as they are easy to drive, crystal clear, defined, excellent mids and lows, highs are not shrill but rounded, and the soundstage so well defined

I own the Dt 990 pro's as well, and comparing the two, it seems like the 990's are more clear mids and highs with muddied and violent bass/sub-bass