They are the Ultrasone HFI-700, used to be called HFI-650, DVD edition. Check out
www.ultrasone.com and, to purchase,
www.meier-audio.de.
How to characterize them? First, they're closed (which would suggest a somewhat truncated soundstage). Second, they are efficient enough to use without an amp (though, of course, an amp can help). Third, they are known for their bass slam, and, having once owned them, I would agree.

Even so, I would not describe them as dark or lacking in the mids or highs - it's just that the bass is perhaps their most distinguishing feature.
There have been some problems noted with their apparently fragile headband.