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Natural Science Forum / Physics / Acoustics / September 2006Equilateral triangle?
Folks, The standard recommendation for a two-channel listening setup is to create an equilateral triangle between the listener's ears and each speaker. That's always worked fine for me! But someone recently asked me WHY this is the standard setup and I had no answer. Is there a historical reason? Was this determined empirically with listening tests? Is there something obvious I'm missing? Thanks. --Ethan >Folks, > [quoted text clipped - 4 lines] >determined empirically with listening tests? Is there something obvious I'm >missing? I just seems natural. There was a center channel in many setups long ago. How its recorded and played back is different from when they first started stereo. Now we have 7.1. I'm waiting for 9.1, with top and bottom, ans 10.1 with vibration. greg > Folks, > [quoted text clipped - 4 lines] > determined empirically with listening tests? Is there something obvious I'm > missing? Well I guess its just for simplicity. Keeping the speakers at equal distances from the listener means a simpler recording and/or play back setup is needed to capture and then reproduce the psychoacoustical trick known as stereo. If you had two sound sources at different distances from the listener (scalene triangle), then there would necessarily need to be delay introduced (either during play back or recording) to produce the desired stereo image. Chris W  SignatureThe voice of ignorance speaks loud and long, But the words of the wise are quiet and few. --- Chris, > If you had two sound sources at different distances from the listener < I guess I wasn't clear enough. Of course both speakers must be the same distance from your head. But the "standard" is to have the speakers the same distance from you as between each other. That's what I'm really asking about. Obviously the speakers shouldn't be two feet apart if they're ten feet in front of you. Likewise, ten feet apart is probably too much in a nearfield setup. But why is the "rule" to have all three sides of the triangle the same? --Ethan In alt.sci.physics.acoustics, Ethan Winer <ethanw at ethanwiner dot com> wrote: > But why is the "rule" to have all three sides of the > triangle the same? Back in my audiophile days I used to experiment a lot with speaker placement. I found that the distance between the speakers was critically related to their toe-in, and that both had an effect on the imaging ability of the system. I found that there was a compromise between a wide, spacious soundstage and a rock-solid center image. I also found that moving my head a few inches right/left and forward/backwards made a significant difference in the soundtage solidity, and that the lessons learned could be aplied to improving the speaker placement. I ended up trying to make the high-pitched tones from particular instruments line up horizontally with the fundementals from the same intstrument, and found thta this was a good technique for arriving at a compromise. If I got everythng right, the soundstage had significant depth as well as width. The equilateral triangle is just a rough starting point. SignatureA nation of sheep will beget a government of wolves. --Edward R. Murrow > I guess I wasn't clear enough. Of course both speakers must be the same > distance from your head. But the "standard" is to have the speakers the same [quoted text clipped - 3 lines] > nearfield setup. But why is the "rule" to have all three sides of the > triangle the same? I think what your asking is more related to the theory of stereo imaging and how the brain reconstructs spatial information from two (or more) complimentary sound sources. Maybe information on http://www.stereosoundbook.com/ would help here Chris W SignatureThe voice of ignorance speaks loud and long, But the words of the wise are quiet and few. --- > Folks, > [quoted text clipped - 10 lines] > > --Ethan I think that is has to do with the angles involved, remember that an equalateral triangle also has equal angles, those being 60 degrees each. Placing the speakers so that the angle formed at the listening point of the triangle is 60 degrees and equidistant to each speaker means that the other two angles will be 60 degrees as well, and this results in an equilateral triangle. This is however, just a rule of thumb, and depending on the type of speakers, the room acoustics, etc, other placements may suit just as well or better. For near-field speakers though, that rule probably works very well in most situations. > I think that is has to do with the angles involved, remember that an > equalateral triangle also has equal angles, those being 60 degrees each. > Placing the speakers so that the angle formed at the listening point of the > triangle is 60 degrees and equidistant to each speaker means that the other > two angles will be 60 degrees as well, and this results in an equilateral > triangle. snip....snip Have another drink and then go to bed an sleep it off, you moron. Thanks guys. All of that makes sense, especially the "it's only a rule of thumb, just a guideline" comments. |
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