Tell the DT 990 PRO that there is no sweetspot on headphones, they will tell you differently.

If that is your logic, why aren’t you using 48 bit or even 128 bit audio? Or what about 256 bit? The bigger the better.

Too bad that stuff is subjective and esoteric as hell. Ten years ago i went down the audio optimisation route for my mixing setup for audio production. I stopped taking it so serious after i read a of a test of some audio production people where the difference between 96khz/24bit and 48khz/16bit was looked into. The result was: when you move some cm out of the sweet spot of your speakers you cannot hear the difference anymore, which is ridiculous.