i just recieved my DT990 today, i have a pair of K701 that i can compare to. however, since the DT990 is not burned in yet, i can only give you my initial impression. out of the box DT990 is more sensitive than k701, despite its 250ohm impedance, it has a brighter/harsher highs than the K701, bass on the DT990 is definetly heavier, and slightly "boomy", most likely due to the fact that its not burned it. wearing the DT990 is EXTREMELY comfortable. possibly one of the most comfortable headphones out there. ill tell you this much. i am willing to sacrifice sound quality for comfort. as far as dt990 goes, its looking to have a lot of real-estate time on my head vs the k701. yes k701 is more detailed and neutral. however, once wearing the DT990 for a whole day. going back to the K701... well just feels like mehhhhhh.
i had the dt990 burning for the whole day now. bass is less "boomy" and more controlled. definetly still deeper than the k701. mids are very detailed, highs still bright, but i believe this is the sound signature of the dt990. overall, great headphone, would not regret this buy - in fact i am really excited to hear what it would sound like when completely burned in