I'm a little excited about old vintage headphone i got today, even though the economic design are not the best but their driver are coating with diamond dust, it's something you don't see often.
Some older headphone use paper diaphragm and probably my favorite. Even though it isn't the best material but it sound is great(for me).
Most modern headphone (even speaker) probably use aluminum diaphragm by now. Of course. There is nothing wrong with it but i find that unattractive when you have a lot of them made from the same material.