Dampening the back of the speaker housing makes a massive difference.
I don't want to say too much just yet, but I'm getting some phenominal results finally getting around to tweaking my MDR-V6, seeing as how it's considerably cheaper than buying a new set of cans. :\
ALL detail is tighter, these headphones are sounding much more expensive now. The stuff I used is silverstone dampening phone usually used for noise reduction.
DT250 pads are entirely unusable after the mod, so I need to find a replacement pad that works, because the stock ones are terrible. The headphones responds wierdly to pad swaps now. the velours are thin, and terrible sounding.
The headphones are now sounding huge, much bigger than such a small headphone should. Bass impact is much punchier, much faster, but also much bigger. It's not what I'd call balanced, but it sounds real. Realler, anyway. Everything tonally but the treble is spot on. I need to try the electrical tape mod to dampen the treble...
High mids need a lot of work now.
Anyway on a quest to turn the MDR-V6 into something worth tinkering with.