Imagine you have a Suzuki Hayabusa engine (that's your HD800S driver) and a Renault Clio engine (that's your cheap headphone driver) they use the same technology, but they are completely different in what they are trying to do, there is no one thing that makes them different, the entire housing, driver shape etc... is completely different from another and everything affects sound in some way or another, look at the HD660S and the HD700 for example, both use the same driver, but the different housing makes them sound very different