Here are some comparison images between the insides of my HD555's and ivant's HD595's.
QQQ said that the HD555 and HD595 share the same drivers, and they certainly appear identical.
This just leaves the actual construction of the two headphones to justify the price difference. The ONLY construction difference I can see is that the HD555's have a piece of foam stuck onto the inside of the rear vents blocking about 40% of the vents. In marketing terms, this would be the "special internal Surround Reflector, which generates an extended spatial sound field,making it the ideal headphone for home theater,as well as music."