Planar Magnetic Headphones - MM vs. MC?

[Cahudson42]

Just curious.. We have both Moving Magnet and Moving Coil phono cartridges. But as far as I know, all planar magnetic phones I've looked at are always 'moving coil' i.e. a powered moving coil film against fixed magnets. Am I correct? Why not a magnetic vapor-deposited film moving against Fixed powered electromagnets?

The film could be very light. The electromagnets Powerful (fluid cooled?) so that they have impedance of 250 ohms or so, so we aren't stuck with low impedance hard to drive coil powered films...

 

[Fluffy]

I'm not an expert, but I guess the reason is – you need a heavy magnet to produce a strong enough field to move the membrane. And you need a light membrane so it can move. If the magnet is light, the field would be to weak. If the membrane is heavy, it would not move well. So the best option is to have a strong heavy magnet that is separated from the light membrane. That means the membrane can't contain the magnet.