Voice Coil Lab Notes: Phase, Group Delay, and Impulse Response - A Quick Primer

This short article by Chris Struck (CJS Labs) is mainly focused on the definition and interpretation of phase, helping to make sense of complex data. This reference article is an expanded version of a previous Lab Note published by CJS Labs, and is certainly a great summary of essential knowledge in speaker design. This article was originally published in Voice Coil, December 2020.

Voice Coil December 2020 offers a diverse set of articles for loudspeaker professionals and anyone in the audio industry. Mike Klasco writes about MEMS Drivers and related hot technologies for 2021. Next up, James Croft discusses a new patent granted in October 2020 to inventor Eric Jay Alexander, and in Test Bench, Vance Dickason characterizes the recent BWX-6501 Midbass driver and the BDT-2901 Silk Dome Tweeter, both from MISCO’s Bold North Audio Line. Now Available in Print and Download!

Passive crossover filter networks for multi-way loudspeakers generally require a resistive termination for optimum performance. The driver itself generally presents a reactive load. Inductive rise with frequency above resonance of the loudspeaker electrical impedance is semi-inductive due to eddy current losses. The L2/R2 impedance model represents the electrical impedance as seen by the amplifier output. An improved compensation network can be realized by using the analogous circuit “dual” of the L2/R2 model. This represents a dramatic improvement to the basic two-component Zobel network and compensates for the non-ideal semi-inductive behavior of the loudspeaker driver across the entire frequency band.

Christopher J. Struck (CJS Labs) discusses all options available for headphone testing and calibration. The article discusses what should be included in a complete headphone test system, considerations on electrical impedance, considerations on repeatability of the results, free and diffuse field corrected responses, left-right tracking, and the use of two-tone distortion measurements. Reference reading material. This article was originally published in Voice Coil, July 2019.

Like the previous conference that was held in 2016 in Aalborg, Denmark, the Audio Engineering Society (AES) Headphone Technology Conference in San Francisco, was a very successful and insightful event for all the participants. The Presidio park venue was also idyllic with the usual crisp waterfront weather. Perhaps too successful, as the event was sold out before it opened.

The AES is set to hold its second International Headphone Technology Conference, August 27–29 at the Golden Gate Club, Presidio, San Francisco, CA, offering three days of presentations, sessions, demonstrations, and more, all dedicated to headphone technology. Mobile Spatial Audio, Individualization, Assistive Listening and Audio for Augmented Reality offer new areas of study and innovation for this year’s conference.

Boston audio and electroacoustic test and measurement specialist, Listen is promoting another edition of its popular 2-day SoundCheck training class on May 17-18th in Elgin, IL (just outside Chicago). This will be a not-to-miss opportunity until the company holds its California SoundCheck and Electroacoustics Training, later in October, in Santa Clara, CA.

When performing electroacoustical response measurements, an important practical consideration is the reduction of uncorrelated background noise. Synchronous averaging (i.e., “complex averaging,” “time domain averaging,” or “vector averaging”) is a technique originally developed to analyze the vibration signature or rotating machines and gearboxes. It can be used to improve the S/N ratio measurement. This article was published originally in Voice Coil November 2012.