AES Section Meeting Reports

Chicago - May 18, 2009

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Floyd E. Toole spoke to a group of about 60 attendees. The talk began with a discussion on the need for accurate sound reproduction and the advantages of multichannel audio. On top of improving spaciousness and envelopment, multichannel reproduction also turns the listening experience into a more social event because of more "good seats" in the room. Unfortunately, the music industry (only 2.1 channels) is not keeping up the movie industry (7.1 channels). Floyd emphasized that "Science and Technology in the service of art is our business!"

Toole then presented a method for measuring loudspeaker performance that is repeatable and correlates with listening tests, debunking the myth that measurements cannot predict perceived performance. The lab measurements take into account direct sound, early and late reflections, sound power and the directivity index. Based on known physcoacoustic relationships one is able to calculate estimated subjective ratings from lab measurements alone. Floyd Toole was able to achieve a 0.86 correlation (1 is perfect!) between subjective double blind listening tests and measurements in the lab on 70 different loudspeakers.

Data was presented showing that above 400 Hz the room does not contribute very much and statistics and geometric acoustics can be safely applied to predict loudspeaker performance in real rooms. Below 400 Hz the room controls the response (2kHz and below in cars!!) and equalization must be applied. However, equalization cannot be used to fix directivity and the loudspeaker performance is the most critical factor above 400 Hz.

Toole continued by showing response measurements of various loudspeakers in different price ranges. Without naming names, he showed that a few loudspeakers in the $10-20k price range were being outperformed by speakers in the $200 range. The discussion was the wrapped up with a discussing of the Sound Field Management system which will use acoustic measurements of your room to optimize the location, level and phase of a given number of subwoofers to yield the most good seats possible.

The Chicago AES chapter would like to thank Floyd E. Toole for a wonderful and educational talk. If you would like to learn more about the topics he discussed you are encouraged to read his book 'Sound Reproduction: Loudspeakers and Rooms'.

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AES - Audio Engineering Society