Back in the middle ages I repaired radios for pin money. The "big"
ones often used a field coil instead of a PM in the loud speaker for
the voice coil "to work against" [correct physics expression]. The
coil did double duty as part of the filter for the HV supply. I
don't remember if they were L or C input filters, but either way I
was surprised -- no audible background hum; still am.