Maybe not something you'd want to dabble in, but I just installed some mods from a small company in the UK in my DT 770 250's which changed them for the better. The main part is pieces of pre-cut open cell foam that fit behind and around the drivers. According to the dummy head measurements by the people who make it, it flattens the response out, bringing the mids up and the bass down slightly, but also slightly extending it (not as if they don't go pretty deep anyway). I have to say, I've now heard deep bass on certain pieces of music (that I know very well) that I didn't know was there, such as in the chorus's of QOTSA's The Lost Art Of Keeping a Secret. Admittedly I haven't owned the 770's for long so I can't make definitive statements about the changes, but they're delivering the eyeball-rattling bass I was craving (that my faithful 20 year-old HD580's don't). ETA >> the mod kits are cheap as chips and the DT 770 is very easy to open up to install them (several vids on YT to guide you).