DivineCurrent
500+ Head-Fier
when i bought the dt990 premium 600 ohm i was devastated by the rolled off highs dulling the sound. seems like they did it to the 900 pro x kinda like the dt880 rolling off the highs. wish they would stop doing it. people think extended highs sound harsh or shrill so they dampen the hell out of it to the point it sounds veiled or at the very least blunted or dull. losing sparkle and shimmer kills the musicality to the point i dont enjoy them at all.
Notice how this guy wont stop ranting about the highs lol:
I did a similar thing
The highs above 8kHz sound really good to me on the 900 Pro X, quite detailed and airy and actually better in that regard than most headphones I've tried. It's mostly the 5 - 7 kHz range that is too forward for my liking, by like 5 dB. But the good thing is it's a very broad and wide bump, so no sharp peaks anywhere. The 900 Pro X is pretty smooth actually. This is coming from a Sennheiser-head, lol. But I know you like the DT990, so yeah I'm guessing you'll find the 900 Pro X too dark/rolled off.
My main complaint is the imaging/soundstage is not much better than the HD650 + 58X and other HD6 models, and it kinda sounds like a semi-open rather than a fully open headphone. The Sundara sounds a lot more open and wide, even if it doesn't have as good treble. Guess that's to be expected from looking at the cup + driver design.