Servo-Control in Mainstream Audio: From Motional Feedback to the Bend-Sensor

Imagine a new class of speaker diaphragm position sensors that enable audio engineers to reduce distortion and extend bass response from studio monitors, soundbars, smart speakers, and even smartphone microspeakers. With the precision of laser displacement instrumentation, this sensor is located between a stationary component of the speaker and an appropriate moving part to provide an error correction reference signal back to the amplifier. Well, that sensor has already been developed. ​This article was originally published in The Audio Voice weekly email newsletter.

In this article for audioxpress, Ed Simon writes: "There seems to be controversy over what testing means in audio. Measuring a difference does not mean you can hear it. On the other hand, if my ears tell me there is a difference between two audio chains and I cannot measure it, that does not mean it is not there. Probably, I'm just using the wrong method to determine audio differences." And after trying to measure all sorts of things to compare which ones sounded fine - or not - he decided the next step would be to build a dedicated more sensitive measurement. This article was originally published in audioXpress, November 2009.

Purifi Audio, the Danish company founded by Bruno Putzeys, Lars Risbo, and Peter Lyngdorf together with a remarkable engineering team, promises Class D amplifiers with record-breaking performance (as well as speakers). Now, Bruno Putzeys made available a detailed report of his investigation on hysteresis distortion, which motivated the development of the company's products. As Putzeys describes, hysteresis in the ferromagnetic material of the amplifier output filter coil is what causes "a recognizable grainy texture in the sound."

Dirac Research announced the debut of Dirac Distortion Control, a patent-pending audio solution that reduces audible distortion in smartphones, tablets, laptops and all-in-one PCs with minimal impact on volume. The company introduced Dirac Distortion Control to the mobile market at MWC19 in Barcelona with a demo experience developed to showcase the next-generation of mobile audio performance in partnership with leading micro-speaker manufacturer AAC Technologies.

This 33-page application note provides an overview of the key electroacoustic measurements used to characterize the performance of loudspeaker drive units and loudspeaker systems, focusing on the most important objective measurements and referring to industry standards for guidance. Download the Audio Precision application note now!

Now launched on crowdfunding platform Indiegogo, the PLASMA Pedal is an interesting innovation in an area where there's hardly been any for decades. The idea for the PLASMA comes from a young Latvian company, Gamechanger Audio, dedicated to infuse new ideas into the musician market. And the PLASMA is certainly new in the fact that instead of the traditional circuits, it sends continuous high-voltage discharges within a xenon-filled tube. In essence - playing a bolt of electricity!

Is the solid part of a loudspeaker motor just a magnet or is there more to it? Simulation tools have helped to create effective and powerful magnet constructions, which make it easy to build a prototype based on calculations and experience. The next obvious step is measuring and listening to the assembled speaker. However, more conclusions can be drawn by analyzing the individual parts further. This article was originally published in Voice Coil, May 2017.

Ethan Winer explains how to "Build the Mojo Maestro," a simple device that allows "subtle distortion" or saturation from any recording or track. Just using two diodes and a few resistors, Winer designed this simple box using the free LTspice simulation software and only half a dozen parts. And the results can be heard on the audioXpress website, with Winer playing multiple instruments, with and without the "Mojo effect." This article was originally published in audioXpress, October 2017.

In this reference article, published by audioXpress in 2008, Joe D’Appolito shares his experiments with loudspeaker evaluation. In the two parts of this article, D’Appolito tries to answer the question: “Of all the measurements available to the designer, which ones are the best predictors of listener preference?" In over 30 years of designing loudspeakers, I have found the following measurements taken as a group provide the strongest predictor of loudspeaker preference available to us today,” he states.

In this article, Steve Temme discusses the issues that are common to testing all types of headphones. As more and more loudspeaker engineers find themselves employed in the fast-growing headphone market, it is important that the unique challenges of testing headphone packages are fully understood.