Non-Linear Amplitude Modulation of Loudspeakers

Even a perfectly linear loudspeaker produces two types of distortions because of the movement of its membrane. First Doppler distortions, a.k.a. Phase Modulation (which the author addressed in his October 2024 article for audioXpress), and secondly distortions stemming from the Nonlinear Amplitude Modulation, characterized in this article. More importantly, this article also addresses how these harmonic and intermodulation spectral line distortions can be minimized and eliminated in loudspeakers.

Because of the movement of its membrane, even a perfectly linear loudspeaker produces Doppler distortion, a.k.a. Phase Modulation, and second distortions from the Nonlinear Amplitude Modulation. This article, originally published in audioXpress, October 2024, characterizes and shows how to eliminate Doppler distortion for a good listening experience.

Read the extended Show Report of the 5th International AES Conference on Automotive Audio. Santiago Rayes (GRAS Acoustics) explains the latest advances in Measurement Microphones for Automotive Testing. Reinhold Lutz writes about Eliminating Speaker Doppler Distortion, René Christensen shares an exercise of Double Bass Arrays, and Joerg Panzer (R&D Team) and Patrick Macey (PACSYS) share their Experimental and Theoretical Investigation of an Unusually Shaped Horn. Jan Didden reviews Bob Cordell’s latest book, “Designing Audio Circuits and Systems”.

Anyone who is serious about designing a loudspeaker using dynamic drivers is either familiar with, or has used, Thiele/Small parameters, generally accepted as ways to predict driver behavior in different enclosures. But there are other measurement methods we can use to determine and quantify nonlinearities: the DUMAX system, produced by DLC Design, and the Klippel Analyzer System by Klippel GmbH. This article was originally published in audioXpress, March 2003.