Electromagnetic speaker with bucking parallel high and low frequency coils drives sounding board and second diaphragm or external apparatus via magnetic coupling and having adjustable air gap and slot pole piece

Claim 1

An electro-acoustic transducer, principally enclosed in a housing, comprising a driving element including a single magnetizable core having one north pole and one south pole that generates usable power producing magnetic energy at both of its poles, where the said core's rearward end produces at least one tenth and not more than seven tenths of the usable magnetic energy as produced by the forward end of said core when said transducer is operating at 400 cycles per second, two electrically parallel coils wound toward the forward end of said core for magnetically actuating said driving element, whereby said coils are supported by said core, wherein said coils are in circuit with and energized by the same electrical power source with one said coil consisting of more turns than the other said coil, wherein the said coil consisting of the least number of turns has electrical current regulating means in series with it, said core being solidly attached toward its rearward end to mounting means providing a magnetic path to said core from magnetic biasing means that will become magnetically pregnant before said core, an armature of magnetizable material for transmitting vibratory motion to a sounding board mounted in axially spaced relation at the forward end of said core, resilient coupling means connecting said armature with said mounting means for permitting relative motion and power transfer between said driving element and said armature element, magnetic biasing means disposed between said mounting means and said armature, wherein separate magnetic pickup means is positioned in proximity to the rearward end of said core for transferring power to energize other apparatus without the use of additional amplifying equipment.