Loudspeaker with two moving coils - has main coil and auxiliary coil which may function as servo or damping element

摘要

The loud-speaker has two coils to control the form of the output signal. It has an auxiliary coil which may operate as a feedback element or as a damping element, and its output can easily be controlled. The loudspeaker has two sets of permanent magents. It has a main moving coil and an extended mandrel for an auxiliary coil. The characteristics of the auxiliary coil may be identical to or different from the main coil characteristics. The auxiliary coil can follow the motion of the membrane of the loud-speaker and can operate as a microphone. The functions of the two coils may be interchanged.