Beyerdynamic Custom One Pro

Some quick subjective impressions (before measurements)

Wow, NO annoying treble. Seems fairly smooth. Very different from T1 or even DT880 - not as bright. Might be a small peak in the lower/mid treble, but not that noticeable and well balanced by the strong bass. The mids are good and are not recessed. Why couldn't Beyer do this FR for the T1?

Little bit of cup coloration. Tap on the outside plate of the cups, and we hear this same sort of coloration - resonance play. Sort of nasal. I doubt the inside of the cups have any damping material. It could probably use some. A layer of dynamic on the inside back of the cups might help too.

Adjustable bass - four positions. I prefer the second. The frequency response measurements will reflect this position which I believe to be the best. The bass is strong, but there is a slight suckout in the upper bass.

Unfortunately, overall fidelity seems low, especially when there is bass. It just doesn't sound very high-fi. Bet you guys highish distortion numbers.