Old 08-17-2010, 04:36 AM   #1
PoopScoop
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Default A Question about acoustical absorption panels.

Im in the process of bulding my own absorption panels from mineral vull, wood and fabric. My soundstage is in my tiny one bedroom appartment and my question is about the symmetry of the soundstage.
My flat is of course not symmetric. From where I sit and operate, the distance to the left side wall is much greater than the right. This off course messes up the stereo image amongst other things.
So my question is this : Do absorption panels allways need a wall behind them in order to be efficient? I got this idea for demping early reflections, that what if I hung two panels from the roof so that both monitors would have an absorption panel hangin at the same distance? The walls will of course be in the same place, but this way I would have a seemingly symmetric way for killing early reflections.
The other option would be, that I mount the right hand panel some inches off the wall and no panel at the left side?
Which would be better?
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Old 08-17-2010, 06:58 AM   #2
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In fact the panels will work even better, when they are spaced a bit and not directly on the wall. Better here means: absorb somewhat lower frequencies.

I had a similar situation, asymetric, with the right side having a wall, the left side open (to the rest of the room). With a mixture of absorption up to 4 inch thick - in front of the wall, spaced by 1/2 inch - I was able to completely solve it.
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Old 08-17-2010, 07:28 AM   #3
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Quote:
Originally Posted by stupeT View Post
In fact the panels will work even better, when they are spaced a bit and not directly on the wall. Better here means: absorb somewhat lower frequencies.

I had a similar situation, asymetric, with the right side having a wall, the left side open (to the rest of the room). With a mixture of absorption up to 4 inch thick - in front of the wall, spaced by 1/2 inch - I was able to completely solve it.
Yeah, I'm aware that you shouldn't mount the panels directly onto the walls in order to get maximun absorption. But the question in my situation is, how do the soundwaves behave after being absorbed/gone trought these panels that I'm thinkin about hangin from the roof (both hangin at an equal, symmetric distance from each monitor) when theres a wall and a window about 2 meters behind the right side panel and an open room behind the left side panel.
Of course in an ideal situation, there would be walls at both right and left hand sides, both an equal distance away from the mixers chair and both treated with identical absorption. However because this isn't the case I'm wondering if I can compensate the asymmetry of the walls with hanging the panels symmetrically.
Did u just place a panel to the right hand side a half inch of the wall, and just left the left hand side completely open and had good results? How far away from u was the right side wall?
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Old 08-17-2010, 07:58 AM   #4
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I guess you are mixing two things.

#1: avoid direct reflection from any wall at the side, rear, ceiling, floor.

This is because the reflected sound will mix with the direct, having a small delay, though. And that causes unwanted combfiltering.

That means you will need the stuff on the ceiling anyway. I have it, its symetrical and it worked really fine.


#2: compensate for asymetry (this time reflection will also - in addition to the above - change perceived volume).


Yes, my left side is still open. (the "open" side goes to where the drum kit is placed and where the mic booth is, distance to those walls 8 meters or so).

The right side's wall is only 2 meters away, rather close. But all worked fine at the end. All listeners love my pin-point stereo image. Centered vocals are perceived dead center from the sweet spot.
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Old 08-17-2010, 11:46 AM   #5
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http://www.bbc.co.uk/rd/pubs/archive/index.shtml

Guide to acoustic practice
BBC Engineering, Architectural and Civil Engineering Department, 1990, Rose

Sound insulation of partitions in sound broadcasting studio centres:field measurement data
BBC Engineering, 1986, Randall, Meares and Rose
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Old 08-17-2010, 12:07 PM   #6
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I have panels hanging from my ceiling an equal distance apart from the monitors without a wall behind them. The walls are different distances. I've had no problems with the stereo image.

Just bringing the panels into my apartment made a huge difference. Once they were hanging, it was even better.
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