The DT 770 Pro is what one would call V-shaped. This means they have a bass and treble boost. Id recommend playing with a bass shelf, starting at around 100Hz and then just increasing the boost to your preference. You can also set the shelf at lower or higher frequencies, all depending on what you like, but don't go to high and ruin the mids.

Same thing for the treble, just set a shelf starting at 5000Hz or so and adjust boost as well as exact position according to what sounds best to you.

What you are basically trying to do, is to get a V-shape, with "correct" mids.

Also, remember to adjust preamp as to "counteract" your highest boost. So, if the highest boost setting is +12dB set preamp to -12. If the highest boost is +29dB set preamp to -29dB. You get the point. This is to prevent clipping!