Or, there are two AT versions - one open and one closed - which differ only by a letter or two in the model number.The comparable closed model appears to be the ATH-A700.
The main spec differences relative to the ATH-AD700 appear to be that the closed model has slightly greater sensitivity, higher impedance, greater extension in the ultrasonic region, and different cable materials. I have no experience with either model.
I would second the suggestions, though, that you consider the Sony MDR-7506. It is a headphone of choice among many professional videographers, among other applications. See the many user comments on it at B&H's site.
I have a pair which I use for non-critical purposes, primarily amateur videography and voice recording, and I've been very pleased. I haven't tried them in my main system, though.
Regards,
-- Al