This is HRTF, it's personalized, the equalization is tuned to sound equally loud at all frequencies. There's nothing closer to linear to my ears - this might not hold true for average ears (DF is derived from those) or your ears.
I've tuned the eq since to be a bit more accurate to flat sounding in the highest end and painted it better, and it looks like:
Now you know why I found VSonic GR07 sibilant. (also, that has some extra resonances)
Edited by AstralStorm - 9/16/12 at 11:18pm