Measurements for Loudspeaker Modeling Files

Loudspeaker modeling files are most often used with acoustical modeling programs such as EASE, Focus, CATT-Acoustic, and others to help determine how well the loudspeakers cover the audience areas and how much “spill” there is on the room’s surfaces. It is important to have accurate data about the characteristics of the loudspeakers that are used in the models. In this article, we will detail some of the requirements to help assure good measurement data for use with loudspeaker modeling. This article was originally published in Voice Coil, April 2017.

Following his original 2008 essay on sound pressure level (SPL) meters, in this article for audioXpress published in March 2015, Ethan Winer considers some practical applications for a basic SPL meter, such as calibrating loudspeaker levels and measuring room acoustics, using a simple Galaxy Audio CM-130 SPL Meter as an example. He then moves on to a more sophisticated model, the NTi Audio XL2.

This Voice Coil Spotlight by Marian Liebig (Klippel GmbH), discusses the specific challenges of Testing Mobile Devices such as Bluetooth headphones, smartphones, and tablets. Those devices have become part of people’s daily lives but increasingly pose important new challenges in terms of quality assurance, where defect symptoms need to be detected sensitively and quickly while measured under tough acoustical conditions.

Michael Kiwanuka’s article “Current Feedback and Voltage Feedback Fallacies” (audioXpress June 2017) elicited comments from Walt Jung, with supporting signatures from a number of well-known designers, to which Kiwanuka responded. Since some editing errors have crept into the article, we decided to make available a complete correct version of the article, together with the mentioned comments and exchange.

Today, most audio products, from Bluetooth speakers to appliances with voice command, now contain at least one microphone. If the product was designed a couple of years ago, it had an electret condenser microphone (ECM), but today it will most likely use a MicroElectrical-Mechanical System (MEMS) microphone. Spec’ing MEMS microphones has some differences and this article touches upon these points.

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.