Practical Test & Measurement: Attenuators for Measurement

In this article for audioXpress, Jonathan Novick explains why the use of external attenuators are an effective and cost-effective way to measure signals above the maximum input voltage of an audio analyzer. Novick explains why there needs to be some consideration of the topologies and different attributes offered by such components for audio noise measurements. He compares the impact different attenuators’ thermal noise will have on measurements of distortion. This article was originally published in audioXpress, March 2019.

Ported enclosures are known to extend the low-frequency output of loudspeakers by exploiting the Helmholtz resonator effect produced by the compliance of the air inside the enclosure and inertance of the air in the port. This article looks at the problem of port nonlinearity to determine the correct port size, and the acoustic impedance of the port under high air velocity. This article was originally published in audioXpress, September 2001.

This article examines the problem of subwoofer placement in odd-shaped rooms, exploring corner locations of subwoofers and some pros and cons of single-woofer versus dual-woofer systems for a given placement within a listening room. In the article, the author extends the analysis and actually generates the “room contribution” curves for a non-rectangular room. This article was originally published in audioXpress, September 2002.

This article describes a DSP (Digital Signal Processing) technique developed to correct loudspeakers’ frequency domain and time domain distortions. Performance improvements, observed using square wave excitation, are documented here in time domain and frequency domain. This article was originally published in audioXpress, June 2010.

From speaker practice and theory, this article on advanced test methods for improving Active Noise Cancellation (ANC) headphone performance attempts to gain better data to draw stronger conclusions about the ANC performance and is a must-read for product developers and anyone interesting in learning how to evaluate those systems. This article was originally published in audioXpress, October 2018.

With the availability of low-cost, PC-based acoustic data acquisition systems, experienced hobbyists can make highly accurate loudspeaker frequency-response measurements without an anechoic chamber. The power of these systems comes at a price. These systems window the time-domain measurement to eliminate room reflections. This, in turn, limits low-frequency response. This article was originally published in audioXpress, June 2012.

Recently, the very existence of current feedback as opposed to voltage feedback has been called into question. This article analyzes and tests simple versions of voltage and current feedback amplifiers and demonstrates some differences in their characteristics. The article provides an excellent overview of historical terminology and how the more modern terms came about and their dependence on context. These articles were originally published in audioXpress, July and August 2018.

On the cutting-edge of current audio industry trends, this article by Jon Schorah explains what you should know about delivering music to Spotify, Apple Music, TIDAL, and other platforms. Jon Schorah explains how to deal with different audio codecs, the effects of masking, Spectral Band Replication (SBS), Parametric Stereo (PS) and others way these services deal with data rate reduction, as well as loudness normalization. This article was originally published in audioXpress, June 2018.

audioXpress readers are well familiarized with Richard Honeycutt's Hollow State column. In many of his articles, Honeycutt explored distortion in a quest to find the origin of “tube sound.” In this article, he takes a more general view of possible amplifier differences, solid- or hollow-state, focusing on different amplifiers’s differences in sounds, and a correct subjective evaluation process of components and systems. This article was originally published in audioXpress, October 2012.

Because every R&D department in the planet is currently looking at implementing voice, and everyone's looking at audioXpress for guidance on how to design a smart speaker, in this edition Kevin Connor, shares his insider knowledge on the topic. Connor, a Cirrus Logic engineer, explains how to provide audio and voice solutions, and design products that sound great and respond reliably to voice commands, regardless of backend service. This article was originally published in audioXpress, January 2018.