Inductive braking in a dual coil speaker driver unit

A bidirectional inductive braking system in a dual voice coil electro-magnetic audio loudspeaker having dual voice coils in a vibrating voice coil/diaphragm assembly driven from an audio source, said braking system comprising:

• a frame of said loudspeaker;
• a vibratable diaphragm assembly having a cylindrical voice coil form;
• suspension means for mounting said diaphragm assembly to said frame;
• a first voice coil affixed to the voice coil form disposed within a first magnetic field that traverses a first annular gap;
• a second voice coil, affixed to the voice coil form spaced from the first voice coil by a voice coil spacing dimension, disposed within a second magnetic field that traverses a second annular gap spaced from the first annular gap by a gap spacing dimension;
• and
• a braking coil comprising at least one turn located on the voice coil form substantially midway between said first voice coil and said second voice coil, said braking coil being configured and arranged to have two electrical nodes each corresponding to an end thereof;
• a pair of terminals, connected respectively to the two nodes of said braking coil;
• braking coil enabling means having two nodes connected to said pair of terminals so as to form a loop circuit including said braking coil and said braking coil enabling means;
• the voice coils and the magnetic fields being relatively dimensioned and arranged to cause said braking coil, (a) upon approaching a first limit of working displacement, to enter the first magnetic field and thus exert a braking force on the voice coil/diaphragm assembly, and (b) upon approaching a second limit of working displacement opposite the first limit thereof, to enter the second magnetic field and thus exert a braking force on the voice coil/diaphragm assembly;
• thus said braking coil is enabled to bilaterally constrain excursions of the voice coil/diaphragm assembly.