I have had two pairs of DT150 crossing my hands, they too sound a little different to one another.
I am weary of excessive volume for the break in. The tool I always recommend is the Isotek System Enhancer and Rejurvenation disc, does a fine job with no side effect I can detect.
Just keep the volume at reasonable level, if no haze somewhat below normal listening level. Isotek make it explicit that high volume would not speed up the task.
The disc includes a track for warming up the system each time before listening.
Edited by Greeni - 11/16/10 at 1:20am