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, written by Anthony Caiazzo, Chief Technology Officer and Principal of Countervail Products, details the company’s family of vibration canceling materials featuring a patented approach that has been shown to provide exceptional levels of vibration damping in many common structural configurations. Countervail materials not only cancel vibrations, but they also contribute to the stiffness of the structure and typically don't significantly change the component manufacturing process.

Detailing a different perspective on signal processing, Stefan Liebich and Johannes Fabry bring us the story of how Elevear is exploring what is possible with Active Noise Cancellation (ANC). Offering a great overview about how signal processing works for ANC and transparency in true wireless earbuds, the two Elevear technical minds share their perspective on how the technology roadmap is taking us in exciting directions.

This article describes how Audioscenic's Amphi Technology effectively enables an evolution in 3D sound and immersive reproduction through loudspeakers. Audioscenic developed a sound reproduction technology that allows for the real-time adjustment of spatial audio systems, providing an effective and natural ability to hear in three dimensions without the need for the listener to be constrained within a specific sweet spot.

This article reviews a patent awarded to Teppei Yamada, on behalf of Zorzo Co., Ltd. (Tokyo, Japan), describing an original design of a low-frequency enclosure system incorporating multiple woofers inter-coupled in a manner similar to what is known as an isobaric or compound woofer enclosure. James Croft reviews other approaches to the concept, starting in 1954 with a patent granted to Harry F. Olson on a dual, compound woofer system and later "reinvented" and popularized by Linn Corp., in 1975. In the new patent, the inventor uses an enclosure with as many as 12 woofers, all seriously coupled through individual air chambers

This article is a detailed review of the intriguing AVAA C214 Digital Active Bass Absorber from Swiss studio monitor and high-end speaker specialist PSI Audio. The concept is more or less the same as the AVAA C20, which PSI launched in 2017. the first commercially available analog active bass trap. Now, with the AVAA C214, PSI has introduced a digital controlled active bass trap that's better suited to deal with room modes below 150Hz in listening spaces and small studios rooms. For this review, the solution was tried and tested in two different spaces and applications.

This article reviews a patent awarded directly to inventors Anthony Allen Bisset (Oakland, CA) and Quang-Viet Nguyen (Aldie, VA), for a coaxial horn speaker design. In his review, James Croft looks back at multiple multi-driver horn topologies and compares the unique aspects of the CCPS Horn Speaker System, highlighting the positive attributes and benefits of the invention, to deliver both increased acoustic quality and increased power density.

This article offers a timely update about the evolution of measurement microphones and the reasons for common choices for automotive measurement applications. The article also expands on current discussions about standard approaches for automotive in-cabin acoustic measurements, including the recent AES TC-AA proposed measurement techniques for automotive audio. A great overview of how measurement microphones can meet new requirements, given the emergence of new technologies, new infotainment options, improved calls, active noise cancellation, and rising consumer expectations.

The market for True Wireless Stereo (TWS) earbuds has seen significant growth driven by advancements in technology and increasing consumer demand for high-quality audio experiences. Hybrid designs, which incorporate two types of drivers, are steadily entering the market as an option that allows OEMs to deliver superior sound quality. This article explores how different hybrid driver configurations enhance audio quality, user experience, and acoustic precision.