Acoustic Panel placement question - AVS Forum
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post #1 of 10 Old 02-14-2007, 08:13 AM - Thread Starter
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Hi all.

Got a question about treating my first reflection point.

Quick diagram attached to show you what I mean below.

I purchased some acoustical panels from GIK (fantastic company to deal with BTW).

I have a panel at my first reflection point (Red).

I have an extra panel and am wondering if I need to put it in the green area?

Since that far wall is over 18' away and partially blocked by the stairwell walls I am not sure if it would do any good there? My screen and speakers are blocked by the right hand side (stairwell walls) so wouldn't all the reflections just happen there?

Thanks for any suggestions
LL
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post #2 of 10 Old 02-14-2007, 09:10 AM
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I couldn't open your picture. It comes up blank. It's labeled as a JPEG, but the picture looks like a BMP file.

Not sure of your specifics, but you will have a few first reflections. Unless you have a VERY wide acoustic panel, it probably isn't covering all your first reflections. In my room, my first reflections cover most the side walls from the front to the listening area (give or take). That's because I did it from all three seats in the front and back, and not sure your setup. If you do the mirror trick, remember to do the first reflection for the Left Speaker, the Center Speaker and the Right Speaker on both side walls. It's good to cover the front wall as well, so if you have extra, you could use it for the front wall.

Tony
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post #3 of 10 Old 02-14-2007, 10:20 AM - Thread Starter
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Pic should be fixed now.

I realize that I will not be covering all the reflection points with this one panel but am just wondering if it will really do any good at all there. Panel is 24"x48".

I will have to take down a nicely framed poster to put up the panel and don't want to bother if it will not help acoustically.

Thanks for the response.
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post #4 of 10 Old 02-14-2007, 10:24 AM
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If you can see the reflection of the speaker there, probly would do some good I guess. Im no acoustitian, but makes sense to me.

You can make your own panels you know.... might be a pain acquiring the OC703 and GOM, but probably cheaper in long run.
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post #5 of 10 Old 02-14-2007, 11:22 AM
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Maybe the experts can jump in here. Now that I see your picture, I see what you are talking about with the stairs. Typically, you want an equal size panel on the opposite wall, directly across from the other one. You may not be able to see the RIGHT speaker in a mirror, as it's blocked by the stairs, but you need to check the area to determine if you see the other two speakers. You may still be getting 1st reflections at that point from the Left and Center speaker. Put a mirror near your steps on that section you have drawn. You are probably getting some reflections from there too so you can treat in that area.

I agree with the above poster. DIY panels are much cheaper, so you can afford to experiment a little.

Tony
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post #6 of 10 Old 02-14-2007, 01:20 PM
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Agree with Tony that if you can see any of the speakers there you should probably treat it - not to mention keeping symmetry in front of the listening position as much as possible.

Bryan

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Bryan Pape - Lead Acoustician
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post #7 of 10 Old 02-15-2007, 08:00 AM - Thread Starter
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Thanks for the advice all. Appreciate it.

Bryan, if I don't see this area on the far wall as a reflection point and decide not to hang the panel there do you think positioning it horizontally behind my center speaker on the floor below my screen would be a good choice for a use of this extra panel? It is a 2" thick one btw. Any other places that I may be missing?
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post #8 of 10 Old 02-15-2007, 11:46 AM
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FWIW:

I have read in more than one place that the placement of panels behind the front speakers and on the back wall did more for sound improvement than any effect of side panels, in the opionion of the people placing them. Anectdotal, but something to think about.

The panels I placed on the wall below the screen made a very noticeable difference in dialog staging. Much more precise.

Chris Whitworth
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post #9 of 10 Old 02-15-2007, 12:17 PM
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A popular type of acoustic treatment method is LEDE (live-end dead-end), it is where you basically make the front of the room very dead (absorbtion) and the rear of the room is made acoustically live (diffusers and reflectors).

The basic run-down for a LEDE room is:
-Front wall as dead as possible.
-First reflections from LCR are absorbed on floor, ceiling, and side walls.
-Rear wall has diffusion to break up any slap echoes from the LCR
-Where the side surrounds are placed on the side wall, behind the listening position, the side walls are live and reflectors and diffusors are used. In front of listening position on the side wall, there is absorbtion to catch the first reflections of the LCR.

-Chris B.



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post #10 of 10 Old 02-15-2007, 01:18 PM
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If you have extra, I'd likely put them on the other side wall also just for symmetry.

Panels behind the speakers provide 2 benefits:

- The act to help kill reflections off the front wall from the surround field. The whole front wall should really be treated.

- They deal with SBIR, irregularities in bass frequency response both peaks and nulls resulting from the proximity of the speaker to the front wall (and side walls). Bass radiates spherically. Some of the energy wraps around the cabinet and bounces off the front wall to come back and combine with the direct energy from the driver. Some is in phase (causes peaks) and some is out of phase (causes dips). Treating the wall with something thick enogh will reduce the intensity of the reflected waves thereby causing it to have less interactive effect on the overall response.

Bryan

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Bryan Pape - Lead Acoustician
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