New owner of the DT 990 Pro here. I had quite high expectation for it before it arrived, after been reading reviews/feedbacks for weeks. I was previously using DTX 900 32ohm with Asus Xonar DGX and really fell in love with the warm, detail, clean sound signature from Beyers. Supposely the DT 990 Pro is an upgrade but apparently I'm not really satisfied with what I'm hearing from the 990 Pro.
It's still on its 3rd day burn-in but I also feel that my Asus Xonar DGX have more the blame for under-amping the 990 Pro even on highest gain (excitor mode). I know for a fact that the DGX is recommanded to power headphone up to ~150ohm so the answer is clear here. From what I can hear now is that the vocal(mid) sounds recessed, and distant. Bright treble with a sense of harshness and very noticeably sibilience. I do appreciate its bass capability and I can feel its energy. It's punchy, controlled, deep, well extended and have good depth and definition.
One thing for sure is that DT 990 Pro sounds A LOT like the Beyer DTX 900 I fell in love with years ago, but maybe because the DTX 900 is 32ohm which is easier to drive so it ended up surpassing the "flagship" DT 990 Pro for 3x of the price of DTX 900 (Original MSRP of DT 990 Pro). DTX 900 sounded fairly neutral and performed well in all 3 bass/mid/treble categories for headphones under $150. I know I've been saying a lot more positive about the DTX 900 than the DT 990 Pro but I hope to improve the sound on the DT 990 Pro as I upgrade my soundcard to Xonar STX with upgradable op-amps (3x LME 49990) - I read those op amps give warm sounding which tailors nicely with DT 990 Pro. I also read that Tube amps (coloration) may work nicely with DT 990 Pro but some tube amps are in fact V-shaped which I'm afriad it's going to exaggerate the already v-shaped present on the DT 990 Pro. Overall I think the DT 990 Pro sounded "nice" but not even remotely close to its full potential I'm afraid. I'd appreciate more inputs from experienced DT 990 Pro owners here