[jlw]

What is the difference in these headphones?

 

[sgrossklass]

Among others that the search may know more about, the frequency responses alone highlight a few differences:
http://graphs.headphone.com/index.ph...nnheiser+HD580
http://graphs.headphone.com/index.ph...rdynamic+DT990
HD580: A bit on the warmish/laid-back side, slight midbass hump.
DT990: Plenty of bass, sparkly highs, recessed mids. More of a "fun" headphone, not everyone's cup of tea.
Have a look at LTUCCI1924's recent DT990 thread.

 

[augustwest]

It would be easier to recommend one or the other, if we knew what sort of music you listen to primarily? They have quite different sonic signatures.

- augustwest