If you add a headphone socket to your DT770s, you'll need to plug the original hole or else the frequency response is terrible. I printed this part in TPU, and squeezed it into place. Stays in on its own, no glue required! Way better than the bit of gaffer tape I had covering it before.

Printed with 40% infill, 3 walls. I turned down the solid infill threshold area to make sure it still had some squish to it.