Still- most headphones don't employ crossover circuits, right? Damping factor has always been a source of mystery and confusion for me. I have a bad feeling that there's something fundamental that's lost in the simplification that allows to talk about damping as it's done in popular circles. As far as I know there is mechanical and electric damping, loads can be resistive, reactive and inductive that may or may not change at certain frequencies. And then there's people who like driving orthodynamics on a SET amp.
Go figure.