ParsonsMatt
Alas, Tyranny
After AB-ing, Senns HD-280 Pro (my friend has a pair too, so I know 'em pretty well) are lacking in bass and subbass + have somewhat agressive higher mids. Do not want. I'd think the HD 25 might be similar, but after a bit of researching it's not. However...
Take a look at the Audio Technica ATH-M50, they sounded many lightyears better IMO and did not seem to have any unequal frequencies.
Many peeps on here have them, like Marcus.
For the record I ABed Senn HD 280 Pro, Sony MDR V6, Beyerdynamic DT 250-80 (DT770 is too bassy for mixing IMO) and AT ATH-M50. They're written in the order I preferred them, from worst to last, and from a mixing standpoint as well of a listening standpoint.
+100
I have the HD280s and the M50s, the M50s blow the 280s right out of the water. The HD280s are thin and harsh with almost no low end. The M50s have pretty solid response down to 40Hz...
The 280s are much better for tracking and live performance, though, due to their isolation properties. Which makes sense, because the 280s are really more for tracking/isolation than they are for mixing, even the Sennheiser site says so. But for listening/mixing? M50s, every time.