[Seth In Mass]

I got this set to use with a Line6 POD HD guitar amplifier modeler, because its spec sheet says to use headphones with a 150-600 ohm impedance.
 
Up until now i've been using the Grado SR80 (32 ohm), and the Senn HD280 Pro (64 ohm).
 
I've noticed a problem with the high notes when listening through the DT880. the high notes sound fizzy/hissy, almost like there's a bit of sand on the headphone speaker. where as both the grado and the sennheiser's high end sounds smooth and clean.
 
i've read about people breaking in their headphones to improve the sound quality.
i've been using the grado and the senn on both the POD HD, and with music and movies, so i imagine that they are more broken in by now than the DT880
is what i'm hearing in the upper register a natural occurrence with brand new headphones?
Would the DT880 benefit from a break in period?
What is the method of breaking in this particular headphone, or headphones in general?
 
i like the sound of the grado over the sennheiser. and i think if this fizzy/hissy issue can be worked out, i will probably like the beyer even more. 
 
thanks in advance for your help
 
edit: i have no idea if the grado or the senn had this same hissy/fizzy upper register issue when i first got them. back then i wouldn't have even known to listen for that type of thing