The membrane will only vibrate at the speed of the signal it is given, so a Planar will replay 1000Hz the same way a dynamic Wil lvibrate 1000Hz. They both play the same source. What we can observe here are the decay, reflections, resonances involved with the headphon'es design (closed back, ported back, good seal/sound leak from the pads, etc) and this affects the sound signature significantly.