Digital compensation of nonlinear distortion in loudspeakers

The authors present a method to compensate for loudspeaker distortion in real time by nonlinear digital signal processing implemented on a digital signal processor (i.e., the TMS320C30 DSP). Based on the literature, an electrical equivalent circuit of an electrodynamic loudspeaker is developed, resulting in a linear lumped parameter model. The parameters in this model are matched with the measurements of a selected test loudspeaker. The linear model is extended to include nonlinear effects by developing the parameters as a function of the voice coil excursion of the loudspeaker in a Taylor series expansion. The resulting nonlinear system is described by a Volterra series. On the basis of this description, an inverse circuit is designed for the second-order nonlinear distortion. This circuit was implemented in real time on the DSP, using a high-level design and code generation system. Simulations and experiments are presente

Digital Compensation of Nonlinear Distortion in Loudspeakers

this paper two loudspeakers are considered; a loudspeaker for reproduction of low frequencies (woofer) and a horn loudspeaker. Instead of improving the behavior of the two transducers by constructional means we apply a feedforward nonlinear digital inverse circuit. Results of a Volterra compensator for the woofer show a significant reduction of the second order harmonics at low frequencies, leaving higher order distortions unchanged. To the horn loudspeaker a more direct method is applied. This loudspeaker suffers from distortions caused by the adiabatic behavior of the air volumes in the compression driver. With this compensator we obtain a reduction of harmonic distortion, in the frequency span from 600 to 1100 Hz. 1 Introductio