Here's a cursory review while I wait for my amp to come in. My setup is currently SoundBlaster Titanium -> FiiO e5 -> Ultrasone Pro 750/900. Immediately you can tell that my amping component needs some upgrading, but I can say confidently that I'm still getting good sound although I'm not sure how much the sound will change with proper amping. I'll write up a better review (and a new thread) once the amp arrives.
Build Quality, Comfort & Isolation for both:
First the build quality of both the Pro 750 and 900 is excellent. They feel sturdy with high grade plastic on the outside of the headband and a soft touch coating at the top. Picking up the headphones one can tell that it's a quality product. Both cans also have the ability to fold up quite nicely for transporting.
Both headphones are comfortable. Clamping force feels a little stronger on the Pro 900, but only ever so slightly. They both provide a good seal and the velor pads don't get too hot. There's also a velor cushion at the top of the headband so they can rest comfortably on your head.
Isolation is similarly excellent for both headphones with very little outside noise getting in, although some noise does get out but it's low enough that you should be able to wear these in a quiet environment without disturbing anyone.
Pro 750 Mini Review:
Right off the bat these feel like some aggressive headphones. Presentation is forward with guitars and vocals coming to the front hitting hard but still controlled. Many people on the forums think the upper mids and treble are harsh on the 750 and although I don't agree with them I can see why they would feel like that. The upfront mids and treble make me feel involved with the music, but can get fatiguing after a few hours. I've heard some slight sibilance on some tracks, but it is a rare and minor occurrence.
The bass has a strong kick and presence without sounding bloated. It is tight and well controlled. I can clearly feel the bass drum being hit. On some electronica tracks where the low end is prominent I swear I can feel my ears vibrating to the deep bass. These are definitely wonderful cans for electronic music - Infected Mushroom has never sounded so good. Don't be mistaken though - the bass rarely overpowers - mids and treble come through clearly.
S-Logic seems to work for me as these have a much wider soundstage than other closed cans I've listened to.
Pro 900 Mini Review:
As soon as I put these on I can tell they are more laid back than the Pro 750. Everything feels more balanced and smoother than the 750. The big criticism with the 750s (harsh treble and mids) should be solved for most people with these. While it still present and clear the mids and treble feel further away and are no longer far in front of everything else, due in part probably to the slightly wider soundstage. This makes certain tracks less involving than the 750s, but the 900s offer more of the sound signature that I think most head-fiers are looking for.
Like the 750s bass is strong. In fact it's a little bit stronger, but not by much and it feels less aggressive. If I weren't A/Bing the two it would be very difficult to point out differences in bass. Still tight and controlled the bass goes deeper than the 750s, but doesn't feel as "in-your-face" as the 750s on some tracks.
S-Logic Plus seems to widen the soundstage. I feel like this helps the 900s have a more balanced sound.
Major differences:
The Pro 900 feels more balanced with a slightly wider soundstage. Where the 750 feels like front row, the 900 takes you a couple seats back. Bass reaches slightly deeper on the 900 as well but not by much.
If I had to choose between the two I'd take the Pro 900, although there are quite a few tracks, particularly electronica, where the 750s more forward presentation beats out the 900.
I'll have more to say once my amp comes in! I'm a novice so if there are any details I've left out or people would like to know please let me know.
