The AD700's are an extremely clean/clear, open sounding headphone and non-fatiguing even at LOUD volumes. The biggest knock on their sound signature I find is their lean bass response. They also have a slight treble roll-off but overall I wouldn't consider them to be in the class of innacurate headphones.
They are really good headphones for orchestral/classical enthusiants because of their unbelievable wide and open soundstage. Not "boxy" or "forward" sounding like you get with a lot of headphones in their price class, especially the closed models.