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In Reply to: Speaker positionin: Truth of timbre/no listening fatigue or imaging/soundstaging but not both. Which to opt for? posted by jaybar on February 24, 2001 at 00:17:24:
I vote for the second type of position with the speakers wide apart but relatively close to the side walls (30") - it will work if you use treatment at the site of first reflection, using mirror to locate tweeter from listening position. My set is similar and I did not like sound of any other speaker positioning/futz as much. I used the same carpet as is on the floor and cut out in triangles (looks like retail corner treatment - i have double sided ones at room/ceiling corners as well) with fabric border, so it looks nice/decorative enough for WAF. Cheap, and made me realize how much the room reflections govern what you hear. Results make your room sound like recording venue and well worth all that cutting of carpet remnants :-)I bet eggcrate would work just as well but not necessarily match room.
Follow Ups:
Thanks for the suggestion. It really would not work. I have an original museum quality art poster on a plexiglass box on the left side wall. The poster is 72 x 36 mounted horizontally. The first wall relections fall in the area of this monolithic poster. The poster is the centerpeice of the room and not movable save for domestic revolutiion. The posters on the right wall, framed in glass, can more easily be removed. At the suggestion of Michael Green, I have hung pillow-type products behind the posters, bookcases and record racks to burn off energy traveling along the walls. Not as good as removing the posters, but the best I can do for the moment.
Hello,If you must go with a reflective surface, you might try placing the speaker extremely close to the reflective surface. That way the reflected sound's delay to the source sound will be at its minimum. I believe it's the Haas effect that states that a "quick" reflection is interpreted by the brain as part of the original sound and does not affect the imaging as much as a reflection greater than 40 ms would.
Given the size of the room and the concrete floors and ceilings, some wide band absorption might help just to cut down the reverb time.
Regards,
Michael Nathan
You bring up a good point, Nathan.The "precedence effect" is a psychoacoustic phenomenon identified by Helmut Haas in his landmark paper, "The Influence of a Single Echo on the Audibility of Speech" (Jornal of the Audio Engineering Society, March 1972), and is sometimes called the "Haas effect".
At .62 milliseconds after the first arrival of a sound signal, the precedence effect starts to kick in, and repetitions of the original signal (i.e. reflections) will have relatively little effect on the apparent direction of the source as long as they sound like the original signal. This .62 milliseconds is the time it takes for sound to travel 8 1/2 inches, and corresponds to the distance around the head from one ear to the other. The precedence effect lasts for about 40 milliseconds, and by suppressing directional cues from these early reflections enables us to determine the actual direction of a sound source in a reverberant environment. For example, you can close your eyes and instantly point your finger right at a person speaking to you from across a reverberant room, even though perhaps 90% of the sound reaching your ears is reflected sound coming from different directions.
Another example of the precedence effect is in multi-channel playback - if the "reflection" from the surround speakers reaches the listener before the original signal from the mains, then the surround speakers are easily perceived as sound sources. As long as their "reflections" arrive more than .62 milliseconds after the original sound, their presence is masked by the precedence effect. Note, however, that if the tonal balance of the surround speakers is significantly different from the mains, then the precedence effect can't effectively mask them, and you could start to hear the surround speakers as secondary sound sources.
Getting back to the situation in jaybar's room -
A sufficiently strong reflection will tend to shift the apparent sound source. Refractions (like off a bookcase edge or perhaps picture frame edge) are especially prone to shift the apparent sound source (smear the image).
Positioning the speakers close to the reflective surface is probably not going to help - in fact, I think that would make things worse, as the reflection would become stronger. Note also that the spectral content of the reflection off the glass surface is going to be "brighter" than the original signal - and this will tend to decrease the ability of the precedence effect to mask the reflection, resulting in image shift.
It is possible to put a thin decorative plant roughly between the tweeter and that reflective framed poster? It doesn't need to be real bushy - just something to diffuse the sound enough to prevent a strong reflection from occuring. Maybe a slightly leafy young bamboo thing.
Just a thought.
What is meant by extremely close? 2 feet? less?Thanks
Jay
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