Very convenient and robust processes. Sounds good, low-mass diaphragm, the detail and come back to life is everything. If not for these two peaks at 6.5 kHz and 9 kHz would be, if you had the perfect headphones. We are like the equalizer on one has almost a reference headphones. If you operate it without equalizer, the treble (sharp hiss) can be troublesome in the long run. Why Beyerdynamik is not correct this shortcoming mystery to me.
One often reads that one of the DT990 250 ohm amplifier needed because otherwise he plays too softly. That is nonsense, in my Asus D1 without KHV it can be very loud, if necessary, because it has a very slight spontaneous membrane with high sound efficiency. I rarely had more than 30% total volume.