NONLINEARITY COMPENSATION FOR HARMONIC DISTORTION OF DIRECT RADIATION LOUDSPEAKER

摘要

For large input signal with low frequency component, the radiated sound from an electrodynamic loudspeaker is significantly distorted due to the nonlinearities of the loudspeaker. The suspension, damping, and magnetic flux of the loudspeaker are the main sources of the nonlinearity. Such electromechanical parameters related to harmonic distortion have been mathematically represented by a polynomial model in terms of diaphragm displacement, while each of the polynomial coefficient is evaluated by using the principle of harmonic balance, experimentally. Based on the polynomial model, we designed a compensator for nonlinear harmonic distortion of direct radiator loudspeaker. Thau observer is used to estimate the displacement of the loudspeaker diaphragm which is rather difficult to measure directly from the conventional experimental method. The usefulness of the designed compensator is demonstrated by numerical simulations and experiments. Simulation and experimental results show the decrease of about 30 db and 12 dB, respectively at the second and the third higher harmonic distortions.