Yup, the diaphragm is typically a piece of plastic with a "voice coil" etched on, sandwiched between two magnets with lots of holes in them. The static magnetic field acts against the magnetic field caused by changes in current in the diaphragm's "voice coil". The voice coil in dynamic drivers attaches the dome to the back magnet and moves the dome due to static magnetic field of magnet and changes in current in the voice coil. And since the voice coil is basically an inductor you've got rising impedance with respect to frequency. And since the voice coil is also like a spring, you've got a major amplitude deviation in impedance at the resonant frequency, which aren't in orthos.