Adaptive Nonlinear Control of Loudspeaker Systems

Signal distortions caused by loudspeaker nonlinearities can be compensated by inverse nonlinear processing of the electric driving signal. This concept is based on an adequate control architecture having free control parameters adjusted to the particular loudspeaker. Optimal performance requires a self-tuning (adaptive) system to compensate for variations of loudspeaker parameters due to the effect of heating and aging while reproducing the audio signal. Straightforward adaptive controllers use an additional nonlinear filter for modeling the loudspeaker and for transforming the identified parameters into control parameters. This approach is susceptible to systematic errors and cannot be implemented in available DSP systems at low cost. A novel technique for direct updating of the control parameters is presented, which makes separate system identification superfluous.