Realtime Loudspeaker Linearization

Electrodynamic loudspeakers exhibit a nonlinear behaviour especially at low frequencies which shows up in harmonic and intermodulation distortions. Their nonlinear transfer function can be modeled by a Volterra series expansion and prefiltering of the loud speaker input signal by an appropriate Volterra, inverse filter can reduce the distortions. Problems with real time application arise from the requirement of large computational power to realize Volterra filters of high orders and long memories. To over come these problems approximations to the loud speaker model must be made. This paper presents a new Volterra kernel decomposition with good performance and small computational load. The pre-distortion filters were implemented on a DSP system and tested with several electrodynamic loudspeakers. The results show that the nonlinear distortions can be reduced significantly.