Reluctance Force Compensation for the Nonlinear Control of a Loudspeaker

Abstract: The motor structure of a conventional electrodynamic loudspeaker driver relies on a Lorentz force to move the loudspeaker diaphragm and generate sound. The reluctance force is an undesired consequence of this very motion,
causing the displacement of the diaphragm to be other than that intended based on the Lorentz force acting alone.
In other words, the reluctance force generates distortion in the audio output. Reluctance force compensation
provides a method for controlling the motion of the diaphragm, taking into account the excursion dependent
variation of the voice-coil inductance that generates the reluctance force. Based on a target diaphragm
displacement, a nonlinear control algorithm utilizing reluctance force compensation calculates a corrected drive
signal to drive the loudspeaker, producing a more ideal trajectory of the diaphragm, and reducing distortion in the
audio output.