DT990 Pro
These are just different enough from the Premiums that I felt needed their own rating. Most of what I've said about the Premium DT990 holds true about the DT990 Pro. However, there is a big difference, and that's in it's mid bass. The kind of bass that attacks your senses directly. The Premium DT990 isn't particularly strong in that department, instead doing the lower bowels of bass some great justice for an open can. The DT990 Pro however has some pretty strong emphasis in all areas of bass. The mid bass hits DAMN hard. It was actually a bit too much for me, as I'm quite sensitive to strong mid bass, as I felt like a jack hammer was hitting me directly in the ears. If bassheads were disappointed in the Premium DT990's bass, they need not look further than the DT990 pro, which is a different beast in that category. But that's the biggest difference. The Premium DT990 and DT990 Pro sound very much the identical to one another otherwise, though the stronger midbass actually helped smooth out the treble a bit, so I felt the treble to be considerably easier on the ears. In this case, it trades off treble discomfort for bass discomfort. Still, I'm a special case, so I'm sure most bassheads would welcome the DT990 Pro with open ears. As for virtual surround placement, these are almost as good as the DT770 Pro 80. They do an amazing job, even more so than the Premium DT990's in this regard. That's why I have to rate them very high on the fun list. They are incredibly immersive. If you can handle aggressive mid bass (not bloated or smothering, but just...very strong), the DT990 Pro is one of the best values in headphones. I just wish I wasn't so sensitive to the particular range of bass that it's so good in.
Fun: 9/10
Competitive: 7/10 (the bass while not exactly obtrusive like closed headphones with such a strong emphasis, it is still quite emphasized, so it may distract you)
HD598
You all know it as an improved HD595, which is a consistent fave among gamers, especially those who use virtual surround amps like the Mixamp. My opinion? The hype is well justified, at least when it comes to the HD598. They are incredibly well balanced. Somewhat bass neutral, mid rich, and energetic treble (never harsh) translates to a very promising headphone for gaming on paper. And I'm happy to report that they are ABSOLUTELY phenomenal for gaming. They belong right up there with the AD700 and K701 when it comes to my very faves hardcore gaming headphones. Soundstage? Check. Positional accuracy? Double check. Detail retrieval? Triple check. The trifecta. It's missing nothing for those needs. The bass may be a bit too laid back for those wanting some immersion in their non-competitive gaming however.
I have to note, these are not a typical Sennheiser. It is not warm or smooth. It's bright and energetic. All for the better, IMHO.
Fun: 6/10
Competitive: 9.5/10