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Old 12th December 2012, 03:51 PM   #81
Pano is offline Pano  United States
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I'm interested in room acoustics and thought I might try some room shapes from Louden's ratios found in the link Speaker Dave provided above.
Acoustics Forum • View topic - ROOM RATIOS

I used CARA room simulation software with the exact dimensions given on that page, and also a cubic room of the same volume. Just a completely bare room, nothing but 2 speakers, carpet on the floor and a listener. The results were surprising. If I let CARA pick the best best position for the speakers and listener, none of the rooms are really bad, not even the cube.

I can post some plots and sims, if anyone is interested.
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Old 12th December 2012, 04:08 PM   #82
Jmmlc is offline Jmmlc  France
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Hello Pano,

Yes it's possible!

Prediction of resonances based on the Rayleigh's formula only predict the existence of the resonances but doesn't predict wher are the nodes of the resonances framework.

This is why such prediction based on the Rayleigh's formula should be associated with the use of such software as CARA.

And that's sometime surprising how a little amount of acoustic treatment can improve a theorically bad room.

Best regards from Paris, France

Jean-Michel Le Cléac'h
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Old 13th December 2012, 01:21 AM   #83
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Nice conversation about the sims and all. Now build a cube and sleep...no, listen to music in it. Then tell us more.
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Old 13th December 2012, 03:14 PM   #84
Pano is offline Pano  United States
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No need, I've done it. I've also been in cubic rooms, and neither are great acoustically. However in neither of those was there a choice of placement. The source(s) was fixed in location and the listener pretty much so.
What Jean-Michel mentions is interesting because I started to see this in the simulations.
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Prediction of resonances based on the Rayleigh's formula only predict the existence of the resonances but doesn't predict where are the nodes of the resonances framework.
Where the nodes are certainly makes a difference in a room, I don't know in box.
E.G., in Louden's "best" room there is a deep, sharp null circa 30Hz right in the middle of the room. But if you are not right in the center, you'd never hear it. How this applies to boxes, I don't know.
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Old 14th December 2012, 03:04 AM   #85
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The sound of the standing wave has to come out the cone. If I remember correctly a typical cone has approx. 20 dB of attenuation. Highest pressure will be for nodes between the woofer mounting surface and the opposite side (front to back axial). Placing the woofer on that surface away from nodes of the other two dimensions can help.

For example a tall tower speaker with the woofer at the extreme top or bottom will have the most likely standing wave problem, as in a 1/2 wave resonant line.

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