Ok Ok So I just spend way too much of my time researching the sig pros and I just talked to a few ultrasone reps who assured me that these cans were never intended to be bass heavy, they are actually designed in the opposite direction. With emphasis placed on the mid to high range.
I was also told that their "bass heavy" models are only the pro 900s and the new sig DJs.
Moral of the story hear? Some individuals here on head-fi either don't know what they're talking about or they need more experience before stating their opinions as facts.
IMO, the Sig Pro does everything well which includes bass when called for in the music, not accentuated. The Denon D600 is considered bass heavy and IMO the Sig Pro wipes the floor with them in terms of presence, depth, tightness and punch. There is also a basshead club forum and the Sig Pro has superior bass to several cans on that list, so everything is relative, but also subjective. For example, Tyll Hertzens thinks the AKG K550 is one of the best closed headphones on the market. I can't stand them. We are both entitled to our opinions. There is nothing factual about sound perception, it is all opinion. I would suggest examining frequency charts if you are looking for a more objective measure of a headphone's sound signature.