VC Spotlight: Boundary Effects on Sources at Low Frequencies

A sound source, such as a loudspeaker, will experience an increase in directivity with increasing frequency, as the wavelength of sound becomes small compared to the baffle’s size. Since the baffle the driver is mounted on is larger than the driver, this occurs at a lower frequency than for the driver diaphragm itself. This article was published originally in Voice Coil, July 2016

Within the audio chain, the loudspeaker could be the element that most influences a user’s auditory experience. A loudspeaker is not only the final element that converts electric input into an audible output, but it is also responsible for an increasing portion of the system’s cost, inefficiency, weight, and size, making it a crucial element for the costumer and the manufacturer. This article, published in Voice Coil, May 2016, discusses ways to use digital signal processing to improve loudspeaker performance.

The phase nonlinearity of most second- and higher-order speaker crossovers is illustrated with the step response of cascaded all-pass networks. Audibility issues are discussed. The audibility threshold depends on many factors; reports vary from about 100μS to 2mS. A sufficient amount, though, is certainly audible. This article was originally published in audioXpress, November 2007.

This article shows that in the digital domain, you can implement phase corrections in a very straightforward way, although there is still an approximation involved. My focus here is on compensating for phase nonlinearities in the driver. This article illustrates the problem for the midrange driver in a three-way system, which will be crossed over to a woofer on the low end and a tweeter on the high-end. This article was originally published in audioXpress, January 2011.

When I review speakers, I make a point of doing my continuous (20-second) averaging room/power curves (moving a microphone slowly over a 1 x 1 x 5’ area at head level at the listening couch) with an AudioControl SA-3051 RTA. This gives me a good idea of just how effectively a speaker pair can deliver flat power to a typical listening area. Read this article, originally published in audioXpress, January 2010.

In a previous article (Loudspeaker Sensitivity: What’s a Watt Anyway? April 2010 Voice Coil), I examined the topic of loudspeaker sensitivity and how it may or may not relate to the overall sound pressure level (SPL) produced by a loudspeaker. The output capability of the amplifier driving the loudspeaker is of equal importance to achieving the target SPL from the direct field of a loudspeaker. This can also be related to the driving signal or the intended program material. This article was originally published in Voice Coil, May 2010.

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.

The controversy over subjective versus objective loudspeaker evaluation has raged on for decades. However, to my mind, there is no controversy. These criteria are simply two faces of the same coin. 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. Want to know more? Read this reference article, originally published in audioXpress, September 2008.

This Spotlight reference article details a simple and fast procedure for testing the diaphragm used in microspeakers, headphones, tweeters, and microphones. Meaningful information comparable to Stiffness KMS and Mechanical Resistance RMS of the Thiele-Small (T-S) parameters is the basis for tuning the production process and for communication between transducer manufacturers and soft parts suppliers. This article was originally published in Voice Coil, January 2016.

Setup tables are OK, and alignment protractors have their place. But there comes a time when a vinyl hound can’t quite abide them anymore. Maybe you’re working on an 80s-era direct drive table and find the factory setup is suspect or even way off. Maybe you’re an archivist setting up a spare unit for 45s or 78s. The fundamentals are easy, or rather, they are once you look at them from the proper perspective. This article was originally published in audioXpress, April 2011.