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12/22/14 at 20:43:37


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Placement Questions (Read 912 times)
Steve Deckert
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Placement Questions
01/18/14 at 01:44:01
 
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Hi Steve,

I ordered 8 of you pre-built diffusers. I have a few questions so I can start planning the installation:

1. In regard to my side walls, do you think it is necessary to go three high (thats the highest I can go) if I can only cover my first and second mirror reflection points (two panels wide)? If I go two high, I will have enough panels to go three or four wide. If I go two high and three wide, I can put four panels on my front wall. If I go four wide, I would leave my front wall with absorption until I can afford more panels for my front wall. In either scenario do I need to follow the barker code? I assume that is what you did in the photo of your room of three high and two wide? My preference is to stay two high because three high will cause me mounting problems due to a window cover.

2. Will my side wall diffusers direct sound to my front wall? My ceiling will be diffused but not my back wall. If the only way to get sound to my front wall is by diffusing my rear wall, there will be no need for me to treat the front wall at this time. I am having trouble understanding how non-specular reflections will travel.

3. If I only have enough sidewall diffusion to cover part of my sidewalls, should I extend the diffusion directly across the listening position or extend it further up toward the front wall to help excite front wall diffusion?


As you can tell, writing is not one of my strengths. If any / all the above is not clear enough, just let me know and I will draw the different scenarios.

Thanks so much for your help,




Such good questions, I thought I'd post the answer's here.


Here is how it works...

1) Direct energy from speakers hits your head and ears. You hear the sound.
2) What missed your head hits the back wall which reflects off and hits the side walls which in turn reflect the sound to the front wall located behind your speakers.
3) The reflection from the front wall goes past your speakers and hits your head and ears.
4) The fact that the same sound hit your head and ears twice spaced only a couple milliseconds apart is what causes poor imaging.  This second wavefront must be delayed in time and reduced in volume well outside of the 2.5 millisecond window for your brain to distinguish it from the original direct energy and categorize it as ambience.


With 8 diffusers your best bet is to place 6 of them on the front wall centered between your speakers in a 2 high x 3 wide pattern.  Place the remaining two panels on the side walls, one per wall. Have someone hold a mirror on the side wall and move it until you see the tweeter front he listening chair reflected in that mirror.  Center your panel on that exact spot.

The front wall cluster makes imaging possible and promotes depth that goes well past the wall itself.

The side wall units improve soundstage width, helping the image to float well outside the speakers location.

Adding rear wall units similar to the front wall cluster should square the performance of the front panels, in other words make them work 4 times better.

Of course any time you're just starting out with diffusion it is nice to make free standing panels by attaching legs so that you can move them around and experience the effects they make in different locations.

And remember that doing all four walls vs. a single wall would work not 4 times better but 64 times better.

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rayd
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Re: Placement Questions
Reply #1 - 01/22/14 at 10:45:49
 
This is an excellent read Steve! Thanks!
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Lonely Raven
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Re: Placement Questions
Reply #2 - 01/22/14 at 19:06:45
 

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And remember that doing all four walls vs. a single wall would work not 4 times better but 64 times better.


This line really resonates with me. I've heard rooms with all 4 walls treated with diffusers and also absorbers to handle the lower frequencies. It's pretty amazing - besides the precise imaging, the surround sound like reverb that's in most recordings is amazing. And if the recording actually includes the natural room reverb picked up during the session, your brain actually picks up on that and you're transported there.
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Acetone
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Re: Placement Questions
Reply #3 - 12/04/14 at 22:48:39
 
Glad I found this forum....it has answered a few questions I've had recently.  Question: with diffusion on side walls and front back walls as Steve described...is there a need for diffusion treatment on the ceiling? If yes, what does it gain you?
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Lonely Raven
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Re: Placement Questions
Reply #4 - 12/05/14 at 17:15:58
 

For the same reason that reflection Steve is talking about that hits the back wall, then front wall, then your ears - it smears the sound...confuses your brain as to which is the original sound, and which is that bounced sound. Well the same thing is coming from your ceiling, except it's an even smaller interval - and I believe it can also cause comb-filtering with the direct sound coming from the speakers, as the reflected sound coming from the ceiling is probably out of phase with the direct sound.

An easy test (after you have your diffusers in place) is to tack a blanked to the ceiling in the first reflection point and see if you hear any difference. Lots of studios have an absorber "cloud" because that's a quick and easy way to addressing those reflections. I'm using some 2d diffusers as I found absorbing too much off the ceiling seemed to deaden my treble a bit much.

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deucekazoo
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Re: Placement Questions
Reply #5 - 12/05/14 at 18:18:17
 
Nice!
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Acetone
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Re: Placement Questions
Reply #6 - 12/05/14 at 20:26:42
 
Thanks LR... a good idea. ACE
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deucekazoo
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Re: Placement Questions
Reply #7 - 12/05/14 at 21:37:45
 
Question for LR and Steve,
Would there be any issues with covering the whole front wall with diffusers?
Side walls?
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Steve Deckert
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Re: Placement Questions
Reply #8 - 12/06/14 at 20:27:40
 
The only danger in covering your entire wall(s) with diffusers is the fact that there would be no absorption. I tried this once in a bright, ringy room and the frequency balance of the room remained unchanged as expected.  Diffusion has two purposes;  A) It allows a highly focused sound stage to present itself.  B) It allows for high SPL listening without ruining frequency balance.   While B is seldom a concern for audiophiles who can still hear,  A is very important.  If you had a room with 1/2 pyle carpet over a 1/2 rubber pad and enough absorption scattered around to create a warm sounding space, then the BEST THING YOU COULD DO, is cover the entire front wall behind the speakers with diffusers.  The worse thing you could do is have a flat bare smooth wall surface.

-Steve
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