Just got a pro900 through local fb market. per earlier thread I think this is a revision 3.
Setup - Apple music - iphone - dongle.
Music - 80% metal, 20% rock/electronic/classical
- Clear, quick, and punchy bass, as expected. Really good drums. Sometimes remind me of my HE6.
- I think this can benefited from more amp - right now I only have an iphone dongle available.
- The highs are a bit harsh - likely due to my crap amp - it plays guttural sound like Dying Fetus really well, but for Cryptopsy the fatigue catches up really quick.
- Despite it is a closed back headphone, personnally I would not recommend it for outdoor use. The bass get drowned out easily on the street/public transportation.
- Surprisingly good for orchestra work. Not wide sound stage by any means but the instrument layering is good. The bass again shines.
Some other comment - I think in a crappy amp/portable situation, I may choose my proline 750 over this, simply because of the highs.
Anyone have a good dongle recommendation?
I would rate Pro 900i quite low in my headphone stable but still have this magic presentation for piano and do kind of entertainthough the bass quality is very average though large in quantity and there is not much shining in the mid range or treble either. But it just have that emotion somehow while being quite cold which seems contradictory. Don´t understand how it works but I get stories listening to chopin which on many other headphones just hurt the ears and is quite booring. Main thing is the titanium drivers don´t move so they hit firm and short decay which suite percussive instruments but not so much string instruments I suspect. 
