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In Reply to: RE: Olive and Toole specifically say in the paper - where? posted by David Aiken on January 09, 2008 at 03:07:24
First I want to clarify the issue:
Olive and Toole investigated a single loudspeaker/single reflection situation. You think that their results can be directly applied to the two-loudspeaker/multiple reflection condition, basing this on Everest: ""How about the two-loudspeaker stereo installation? Olive and Toole investigated this and found that the effects obtained from a single loudspeaker are directly applicable to the stereo case. This means that the information presented earlier is immediately available for application to stereo listening situations such as the home music-reproduction room."
I say that, before 1989, Olive and Toole never ever investigated stereo systems with multiple reflections.
In their 1989 AES paper on the detection of reflections they say that "This [single lateral reflection] can be interpreted as a single component of a room sound field, or as a cross-channel delayed component in a stereo or surround-sound system."
If they had the intention to refer to (right and left) lateral reflections in a stereo system, they certainly would have done so. Instead they refer to a “cross-channel delayed component”. Note that they make the distinction between “stereo system” and “room sound field” !!! Do they intend to say that a stereo system is the same as a room sound field? I think that we take it for granted that they don’t! And here is where Everest IMO made a mistake.
They further refer to a “delayed component”. Reflections are ALWAYS delayed so why do they use the term delayed? Clearly they refer to something else which could be for instance a single-channel delayed recorded sound.
When Everest says that Olive’s single loudspeaker/single reflection findings are “directly applicable to the stereo case” he is reading something into Olive’s paper which is clearly not written!!!
That’s why I said that I could not find the passage! The passage I quote simply does not allow to draw that conclusion.
Further, if you look at this case with somewhat greater attention you will notice the following:
When a single loudspeaker/single reflection is present there will be an image shift towards the reflection and/or image spread at levels above threshold, as has been shown by Olive and Toole.
When two loudspeakers/two lateral reflections are present
1. the two loudspeakers will generate a first phantom source and
2. the two lateral reflections will generate a second phantom source
Both phantom sources are, by definition, located between their real sources. An image shift towards the reflection phantom source is only possible when the position of both phantom sources relative to the listening axis is different.
Of course, this is theoretically possible but it entirely depends on the recorded material and positioning of the loudspeakers w.r.t. the room boundaries. In any case this scenario has to be experimentally investigated and in no case conclusions retaling to stereo system/multiple reflections scenario can be drawn from the single loudspeaker/single reflection situation.
Klaus
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