Test Chambers for Accurate and Repeatable Measurements: The New Normal Even for Unique Projects

Hill Acoustics was approached by a company with an interesting problem. To accurately acquire measurements from a prototype that had an array of microphones to detect music coming from various angles of incidence and needed to operate over the full audio frequency range. Having seen Hill Acoustics' Tetrahedral Test Chambers and the results they could deliver, could Hill Acoustics help with this challenge?

Geoff Hill, the inventor of the Tetrahedral Test Chamber (TTC), a member of the international Electrotechnical Commission’s standards 60268-21-2018 and 60268-22-2020, and part of the IEC Working Group TC 100/TA 20/PT 60268-22 on electrical and mechanical measurements on transducers, summarizes the progress happening on loudspeaker measurement standards. This is the first of two articles, appealing directly to all loudspeaker designers and manufacturers. This article was originally published in audioXpress, September 2022.

In this article Geoff Hill completes the Tetrahedral Test Chamber story, a concept born out of necessity, simple wavelength theory and Beranek's wedges, measurement theory, and building upon experience gained in designing chambers in Europe, US, and Asia. These chambers are now in use throughout the world, providing consistent, reliable, and accurate measurements of loudspeaker transducers and loudspeaker systems. This article was originally published in audioXpress, October 2021.

This article revisits the story of the development of the Tetrahedral Test Chamber (TTC), by Geoff Hill, loudspeaker engineer, author, and inventor, in an effort to solve the longstanding problem of making consistent loudspeaker measurements. This innovative loudspeaker test chamber is now defined in international standards and in use throughout the world, scalable to any size of loudspeaker driver. This article was originally published in audioXpress, September 2021.

The October 2021 edition of audioXpress is now available in print and digital. This edition offers a balanced mix of content, starting with our annual market update report on home theater, and associated residential technologies. Brent Butterworth reviews a MEMS earphone design from USound, Geoff Hill completes his Tetrahedral Test Chamber Story, and Bruce Heran writes about refurbishing Altec Lansing Vintage Speakers. Diving into audio electronics, Morgan Jones writes about Ultra-Linear Design; Morty Tarr discusses Cascodes and Folded Cascodes; and Richard Honeycutt talks about the Effects of Negative Feedback. Jump right in!

Spectral Measurement (formerly the Test & Measurement division of Prism Sound) has signed a licensing deal with UK-based Hill Acoustics enabling it to manufacture and sell the company’s Loudspeaker Test Chambers. Hill Acoustics’ LTC range includes a selection of Tetrahedral Test Chambers (TTCs) as well as other geometries that provide test and measurement solutions for loudspeakers, providing an effective, low cost solution that removes the need for large anechoic chambers.