Is there someone that rewinds the high impedance coils used on horn type speakers or headphones? Is there a way to re-energize the u shaped permanent magnets?

Dan: The magnets can be remagnetized by puting them in a coil carrying many amps. Tricky.

Rewinding an open coil would not be much fun either.

My approach is to replace with a little 2" permanent magnet speaker along with a small matching xfmr. They can be fitted into the horn's base.