Quote: Dynamic drivers are only indirectly controled my magnet (if amp's Z out is low enough), the resistance you speak of comes from driver suspension, and that is why some drivers are less sensitive to high impedance outputs- they have stiffer suspension that does most of the job of controlling the membrane. I'm not an expert but it's logical that ortho drivers do not simply sit loosely between magnets but are suspended just as regular dynamics, something holds them in place. Btw there is no magnet attached to the membrane (or ribbon, whatever you call it) in dynamics, just the voice coil. Even if we speak of an open- back ortho like Audeze there still is mechanical damping from the felt or similar stuff that sits behind (and, I guess, in front) of the driver. For example there is a mod for LCD- 3 which uses toilet paper (purrin's idea if I'm right): it simply restricts the airflow allowing less driver movement after it was excited by the signal. As far as my basic knowledge of accoustics goes I can say that orthos are indifferent to output Z variations (and therefore high Z out) at least in FR terms. If they are a purely resistive load you could aim for current bridging. If Z out is equal to the load, then current transfer is most efficient. Low Z out allows for more efficient voltage transfer, meaning more dB at your ears at a given gain, so if you used like 10kOhm Z out to drive 50 Ohm ortho headphone you would need a lot of a gain for satisfactory loudness, and most of the voltage would be wasted into heat.