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ThirdOrder Nonlinear IIR Filter for Compensating Nonlinear Distortions of Loudspeaker Systems
Kenta IWAI Yoshinobu KAJIKAWA
Publication
IEICE TRANSACTIONS on Fundamentals of Electronics, Communications and Computer Sciences
Vol.E98A
No.3
pp.820832 Publication Date: 2015/03/01 Online ISSN: 17451337
DOI: 10.1587/transfun.E98.A.820 Type of Manuscript: PAPER Category: Digital Signal Processing Keyword: loudspeaker system, nonlinear distortion, nonlinear IIR filter, mirror filter,
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Summary:
In this paper, we propose a 3rdorder nonlinear IIR filter for compensating nonlinear distortions of loudspeaker systems. Nonlinear distortions are common around the lowest resonance frequency for electrodynamic loudspeaker systems. One interesting approach to compensating nonlinear distortions is to employ a mirror filter. The mirror filter is derived from the nonlinear differential equation for loudspeaker systems. The nonlinear parameters of a loudspeaker system, which include the force factor, stiffness, and so forth, depend on the displacement of the diaphragm. The conventional filter structure, which is called the 2ndorder nonlinear IIR filter that originates the mirror filter, cannot reduce nonlinear distortions at high frequencies because it does not take into account the nonlinearity of the selfinductance of loudspeaker systems. To deal with this problem, the proposed filter takes into account the nonlinearity of the selfinductance and has a 3rdorder nonlinear IIR filter structure. Hence, this filter can reduce nonlinear distortions at high frequencies while maintaining a lower computational complexity than that of a Volterra filterbased compensator. Experimental results demonstrate that the proposed filter outperforms the conventional filter by more than 2dB for 2ndorder nonlinear distortions at high frequencies.

