There is an underestimated evaluation of the impact that power supplies have on field coil speakers. Makers of field coil drivers tend to minimize this aspect and in general advising the use of switch power supplies or diode based regulated ones. Well with friends we have done some testing on the big systems that are resident to my place, these are fully field coiled no alnico, ceramic or other. But leave that debate to forum talkers. Tungar power supplies are what work best, they demand dedication and not for the casual approach.
Anyway this is a Tungar power supply made for a friend that can power upto 4 amps @ 24 vdc. Yes that is what is needed to push tweeters, mids and bass field coils. More of these will be made. Go here