AES Section Meeting Reports

Los Angeles - May 31, 2020

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Dave Rat was hearing differences between two different venues using the exact same sound system. One was larger than the other. His initial assumption was the difference was in the cable lengths. He verified this by using long cables on one side of the stage and shorter cables on the other side. He was able to hear the difference, so he set out to find a way to measure and hear the difference in a test environment.
Instead of setting up a speaker and doing a blind listening test, or doing a series of measurements, he determined to measure a speaker cable similarly as he would measure a resistor. By probing the ends of one conductor (at the amplifier terminal and at the load terminal) any differential between the beginning and the end of that conductor should be evident, measurable and audible if significant.
In pro audio live touring, venue sizes vary from day to day, so it is necessary to carry long cables that are often used with coiled lengths. A significant difference seemed to result from coiling the cable as Dave demonstrated by uncoiling the cable or by coiling using a "modified figure eight" technique where, by making every second coil run in the opposite direction, the effects of inductance are less.
Two hours were spent testing various cables with various twists, coils and loads. Results varied. Dave has 4 YouTube videos on the subject.
There was an active chat channel on Zoom including one comment that said, "So far, everything heard (and seen) is easily explained by differences in mutual inductance and common-mode inductances - as they interact with resistances, of course."
The test setup included an Ivie IE20B pink noise generator, a small mixer, LA Acoustics LA48A power amplifier, Klark-Teknik DN60 Real Time Spectrum Analyzer, Dorrough 1200 meter, Infinity monitor speaker.
Dave used pink noise rather than music for this demonstration so as not to get flagged for copyright violation.
Viewers included in Argentina, London, Seattle, Iowa, and California.
The Audio Engineering Society Los Angeles Section wishes to thank Dave Rat for an interesting and unusual presentation

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