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Reflecting on Reflections

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[Feature] Spaces for live performances are part of the art, enriching timbres, embellishing direction and space, and enveloping the audience. These spaces are all different from each other, but designed to meet certain acoustical criteria related to the kinds of performances for which they are intended: opera, orchestral classics of different periods, and so on. Creating a strongly reflective, diffuse, sound field that conveys the unamplified sounds from live performers to the farthest seats in concert halls without corrupting the temporal details in the performance is a fine balancing act. This is the domain of traditional acoustics. This is Sabine’s “place.” But things change.

JAES Volume 62 Issue 6 pp. 454-455; June 2014
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Siegfried Linkwitz
Siegfried Linkwitz
Comment posted July 6, 2014 @ 16:06:36 UTC (Comment permalink)

It is about time that the audio industry and academia address the loudspeaker and room compatibility issue for domestic size reverberant spaces and recognize it as just one more problem area in the transmission path from microphone membrane to eardrum. The brain takes over behind the ear drums, creating the perception of an acoustic event in some form of 3D space. The perceived scene is spatially distorted due to the directional characteristics of microphones and their distances to sound sources, and due to the directional characteristics of loudspeakers and their distance and azimuth to the listener. The microphone output signals contain a limited and specific view of the original acoustic scene. On playback the loudspeakers illuminate the listening room. The resulting eardrum signals consist of superimposed streams of air pressure variations arriving from different directions.  With two ears, a movable head, a brain and a mind, evolution has formed a superbly capable perceptual apparatus, which automatically sorts a plurality of sound streams for direction, distance, meaning and for focusing attention.  Loudspeakers and room (also the room behind the speaker membrane) must not provide misleading cues to a listener's brain in order to fully hear the information contained in the microphone signal streams and to instinctively withdraw attention from loudspeakers and listening room. The result is a convincing auditory illusion.

The job can be done. It has been done. A simple stereo system can render in an ordinary room a more convincing 3D illusion than conventional multi-channel surround setups, because it can put perception at ease.
Why has the audio industry not caught on other than trying to put patches on the problem for decades?
Siegfried Linkwitz -

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Bob Olhsson
Comment posted February 23, 2015 @ 15:19:25 UTC (Comment permalink)

I'm pleased to see Dr. Toole talking about what the folks at RCA learned about the importance of early reflection response during the '40s! Combine this with Richard Heyser's work and we emerge from 40 years in the dark ages of listening room design!

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Floyd Toole
Comment posted February 25, 2015 @ 16:58:58 UTC (Comment permalink)

Bob.  RCA in the '40s.  I can only imagine you are talking about the legendary Harry Olson - any relation, the names are remarkably similar?  Yes, Harry contributed a lot of solid engineering, good sense and logical thought to the audio industry, much of it ignored or  forgotten it seems.  I am frequently humbled by the insights of our predecessors, who lacked the high technology measurements and analytical tools we have.  There is a lot of old fashioned folklore that needs to be purged from our industry.  Science is hard work, opinions come easily.  Thanks for your comment.

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Bob Olhsson
Comment posted February 27, 2015 @ 16:45:17 UTC (Comment permalink)

Prior to the '50s Bell Labs and RCA paid some of the highest engineering salaries in the world and it showed in what they accomplished. It's too bad that level of investment is gone. Instead of science we now have mostly multiple myths being argued.

The acoustical treatment for our little studio at Motown was designed by RCA. It was designed to have flat, uncolored early reflections. I found that adhering to this principle has always achieved the best results in both recording studios and listening rooms. It's even logical that early reflections will always color perception and there is no way to eliminate them short of an anechoic chamber.

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