Kenta Iwai

An improved filter employing measured characteristics of diaphragm displacement for compensating loudspeaker nonlinearity

In this paper, we propose an improved filter employing measured characteristics of diaphragm displacement for compensating nonlinear distortions in loudspeaker systems. Loudspeaker systems generate nonlinear distortions that degrade the sound quality because of complicated structure of loudspeaker systems. Therefore, we set out to improve the sound quality by employing Mirror filter which compensates nonlinear distortions in electro-dynamic transducer. Mirror filter calculates linear instantaneous displacement of diaphragm from the linear differential equation of the electro-dynamic transducer and generates compensation signals based on the nonlinear differential equation of the electro-dynamic transducer and the calculated displacement of diaphragm. Hence, the compensation performance with Mirror filter is determined by the accuracy of the calculated linear and nonlinear motion based on the differential equations. However the calculated motion of the diaphragm does not agree with the actual motion perfec...

Modified 2nd-order nonlinear infinite impulse response (IIR) filter for compensating sharpness and nonlinear distortions of electrodynamic loudspeakers

Electrodynamic loudspeakers generate the nonlinear distortions and degrade the sound quality. This is because the nonlinearity of electrodynamic loudspeaker is caused by the large displacement of the diaphragm, in particular, around the lowest resonance frequency. One of the compensation methods for the nonlinear distortions is using mirror filter. This filter is derived from the linear and nonlinear differential equations and designed by second-order nonlinear IIR filter or third-order nonlinear IIR filter. The coefficients of these filters are determined by the physical parameters of the loudspeaker. However, it is difficult to compensate the nonlinear distortions when the sharpness of the loudspeaker is high at the lowest resonance frequency because of large displacement of the diaphragm. Although it is required to compensate the sharpness of the loudspeaker, second-order nonlinear IIR filter cannot compensate the sharpness because of the compensation principle, i.e., this filter adds the nonlinear sig...

Third-order nonlinear IIR filter for compensating nonlinear distortions of loudspeaker system

In this paper, we propose a 3rd-order nonlinear IIR filter for compensating nonlinear distortions of loudspeaker system. The proposed filter is derived from the nonlinear differential equation of the loudspeaker system. The conventional filter, which is called the 2nd-order nonlinear IIR filter, cannot reduce nonlinear distortions at high frequencies because this filter does not include the nonlinearity of the self-inductance of the loudspeaker system. On the other hand, the proposed filter includes the effect of the self-inductance and can reduce nonlinear distortions at high frequencies. Experimental results demonstrate that the proposed filter can reduce intermodulation distortions by 2 dB at high frequencies.

Nonlinear IIR filter considering nonlinearity of self-inductance of loudspeaker systems

In this paper, we propose a novel nonlinear IIR filter considering the effect of the self-inductance in loudspeaker units in order to compensate the nonlinear distortion. The nonlinear IIR filter proposed by Takemura, et al. includes the nonlinealities of the force factor and the stiffness of the suspension except the self-inductance of the voice coil in loudspeaker units. This means that the conventional nonlinear IIR filter cannot compensate the nonlinear distortion at high frequencies due to the self-inductance. In contrast, the proposed nonlinear IIR filter which considers the nonlinearity of the self-inductance can compensate it. The parameters of the closed-box loudspeaker system are estimated using Simulated Annealing (SA), and the proposed nonlinear IIR filter is designed according to the corresponding estimated parameters. Experimental results on the compensation for the nonlinear distortion demonstrate that the proposed nonlinear IIR filter can reduce more nonlinear distortion compared with the conventional one.