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.

This article compares motion feedback technologies applied to speakers. A recognized expert in this field, Reinhold Lutz explores how to achieve a nearly perfect electro-acoustic transfer function, including a detailed control strategy of different types of sensors. A great exploration of how a closed-loop feedback system is able to improve loudspeaker linearity.

The principles applied by Dr. Reinhold Lutz's for precise measurement of the sound pressure frequency response in the presence of room modes, are available in its AudioChiemgau Mode-Compensator solution. Jan Didden and Rens Tellers did a basic functional test to find out how well they could make it work and they were pleasantly surprised with the results. This article was originally published in audioXpress, October 2023.

This article discusses how to measure loudspeaker SPL response and harmonic distortion at low frequencies in a standard environment, full of reflections from acoustically hard boundaries (e.g., walls, floor, and ceiling), room resonances, and even ambient noise reducing the dynamic range and accuracy of the measurements. The method combines near-field measurements with two identical microphones. This article was originally published in audioXpress, October 2023.

In the October 2023 issue of audioXpress, Jan Didden visits Dutch & Dutch, Reinhold Lutz shares a practical way to measure loudspeakers in any room with his AudioChiemgau Mode-Compensator, which is tested by Rens Tellers. We have two DIY open baffle projects from Perry Marshall and Charlie Laub, Richard Honeycutt writes about the Western Electric 91E, and Ethan Winer shares his Popping P Filter circuit. In the Sound Control column, Honeycutt explores Passive Variable Acoustics, and Chuck Hansen concludes his article series on Power Transformers. audioXpress October 2023 is now available in print, digital, and online.