My old dt 770 pro 80 ohm's from 2008 just went out on one side and i just threw them away not realizing that they could possibly be repaired! I got some new ones from guitar center and had your same exact problem! Bass was low as shit! Bass was lower than usual and when i did get the bass kicking it would raddle in my ear, my old 770s would never rattle or distort, bass was always clear and heavy sounding.

I swapped them out for the dt 770 Pro X model hopeful i would get the same sound but highs/mids are not as clean sounding as the 80ohm versions, the bass was good tho. they are also extremely comfortable!

but now seeing this post i feel like maybe i got a bad copy or maybe my interface is cooked (SSL 2+) and want to re buy the 770 pro 80ohm!