Let me preface this review by stating that I used to own the AKG K701. I loved its huge soundstage, detail, and resolution. As an avid Electronica listener, however, I found the bass lacking a bit, so I decided to audition a few headphones that provided the bass response I was craving. I tried out the Denon D2000 and the Beyerdynamic DT990/600ohm. Both were great cans, however, I wanted even more bass (am I a basshead or what?). In blind faith, I sold my AKG K701 and purchased the Ultrasone Pro 900, a decision I am currently recognizing as the finest decision I’ve made so far as a budding audiophile.
The Pro 900s are plugged into a Matrix M-Stage headphone amplifier with an Ibasso D4 being used as a dedicated DAC. I run Foobar2000 with the WASAPI plugin, and most of my music is either encoded in FLAC or 320kbs MP3. 90% of my music is Electronic Dance Music (Trance, Drum & Bass, House, etc) and the other 10% is Metal (bands like Disturbed, Killswitch Engage, Sonic Syndicate, etc). Burn in is far from over, but I’ve run some pink noise through them for a few nights in a row. Having said all that, lets get this review rolling.
Build Quality: The Pro 900 is a tank. Built from very durable plastic, these cans are made for a work environment. While I usually take extreme care for my electronics, voicing my distaste when someone sets my headphones down with even a hint of force, its nice to know that the Pro 900s would be completely fine if I were to drop them. I also really like the looks of these headphones. They're very sleek and modern, and the black and silver color scheme goes well with the rest of my setup (my Matrix M-Stage is black with a silver front-plate).
Comfort: These headphones, while not quite as comfortable as the DT990/600 (what headphone is?), are still pleasant to wear. Their velvet ear cushions are a nice medium between the Beyerdynamc’s pillow-cushions and the K701’s firm, carpet-textured ones. The Pro 900s do have a tendency to place a lot of their weight in a small spot at the top of my head, but I’ve always been sensitive to headphones in that region, with both the K701 and the D2000 causing slight discomfort after long listening sessions. The clamp force is strong enough to keep them in place, but never have I felt that its too tight. My roommate has the M50s, and I find those have much more clamping force than the Pro 900s. These headphones won’t “disappear” on your head, but they’re far from uncomfortable.
The Sound: I will start by saying the bass the Pro 900s provide is phenomenal. It reaches deep, has great texture and definition, and always maintains solid impact. The D2000s and DT990s, while both bass oriented cans, cannot touch the bass the Pro 900s produce. The bass lines in Trance and Drum & Bass have never sounded so amazing. The best part about the bass in these cans is that, despite its exaggeration, I’ve never found it to encroach upon the mids or affect the rest of the spectrum. It always remains well separated and defined, a trait that is hard to find in headphones. The mids, while maybe a little bit recessed, are very detailed and resolving. Female vocals from the likes of Oceanlab’s Justine Suissa sound magical and intimate, while male vocals from singers such as Howard Jones (Killswitch Engage) feel commanding and powerful. The highs extend very far and provide music with a great sparkle without showing off too much sibilance. These cans have amazing detail retrieval and their transient response is incredibly fast. Notes start and end with little decay. Soundstage, while not as vast as the K701, is bigger than the D2000’s and very close to the DT990s, which for a closed can, is quite a feat. Is it the S-Logic Plus? I can’t be sure, but it doesn’t sound like music is being presented in any more of a “3D” sort of way than other headphones. If S-Logic is what makes the soundstage so good for a closed can, then maybe it does work. Regardless of the cause, the Pro 900 has great soundstage and imaging.
All of this makes Electronica an immense pleasure to listen to. The bass hits hard, and goes deep and makes me want to close my eyes and get lost in its vibrations. Vocals hypnotize me, and synths dance through my ears better than they ever had. Metal also sounds very good. The impact provided by the Pro 900 makes each song feel "heavier" and more "in your face." Out of the box, guitars sounded a bit weird and unnatural which really put me off. This has been slowly disappearing as burn in progresses.
In summary, I’m in love. I’ve finally found the right headphones, and will stick with these for quite some time. I whole heartedly recommend them to anyone who listens to Electronica, Hip Hop, or Metal, and wants some amazing bass without sacrificing the rest of the spectrum. A warning though: I’ve read on these forums that many people think the Pro 900s have a strange tonality and really dislike their sound signature. For certain genres, I agree. I DO NOT recommend these if you listen to jazz, classical, or anything were a very natural presentation is needed. Make no mistake, these headphones have huge bass and are made for the Electronic Dance Music genres (or any other genre which requires bass, such as Hip Hop). If you want to unleash your inner basshead and start listening to Electronica the way it’s meant to be listened to, give the Ultrasone Pro 900s a try. I think you'll find them the perfect fit.
Edit: Since I wrote this review, the Pro 900s have been becoming more and more refined. The bass still hits hard, but they sound good with every genre I throw at them. Metal, Electronic, Acoustic, Classical, etc all sound just great on these headphones. I've come to recognize the Ultrasones as some of the finest gaming and movie cans I've ever heard. They really need to be heard to be believed, as its so rare to find headphones that provide great bass while maintaining some of the best positional cues I've experienced. If I had to throw out one negative about these headphones, it is that their left/right channel separation can be a bit pronounced sometimes. Some notes can sound like they are coming from quite an extreme left or right position. This makes the soundstage feel a little less cohesive at times. This rarely happens however, and it is such a small gripe that it almost isn't worth mentioning.