Acoustic Treatment that has WAF

P

papostol

Junior Audioholic
My system is in our living room and my wife is a crazy neat freak. She likes traditional decorations, not too modern.

Are there any room treatments available that I could bring into my system without my wife ripping them down? My room is lively. Wood floors with a big picture window.

Thanks Pete
 
gene

gene

Audioholics Master Chief
Administrator
1) Get a throw rug for that floor. Make sure you put a thick pad below it (act as absorbers).
2) Add thick padded curtains or drapery to the windows. (act as absorbers)
3) Integrate bookshelves with books in them on the back walls behind the listener. (Act as diffusors)
4) Toe in main speakers so the listener hears more direct sound while at the same time it will move the axial side reflections
5) Bring listening position a bit closer to the speakers so that they are hearing more of the direct rather than reflected sound
6) Treat first reflection points on side walls with sone absorption material such as cloth, drapery, etc.
7) Read our Acoustics Section for more tips and guidelines.
 
Az B

Az B

Audioholic
Cover the window with heavy velvet drapes, and if that's not attractive enough, you can hang more decorative drapes in front of them for a little higher WAF.

For wall panels, these are some I made a while back. They're standard acoustical fibreglass panels (Owens 703) with quilt batting and a decorative fabric cover that matches other room decor. The frames are made from one of those 4 fold decorative screens sold at furniture boutiques. I simply installed the panels behind them and mounted them by thier onesies: (Ignore the mess, I was doing a good bit of testing that day, you can see the calibrated mic on a stand in the picture)



Here's a close up that better shows the decorative aspects:



For best effectiveness, the panels should be places at the first reflection points and should be hung with a little space behind them. I would leave the rug off the floor, rugs generally absorb only a very narrow frequency band and can make things worse. Maybe a small throw rug in front of the speakers.


For behind the seating postion you want dispersion. Bookshelves, knick knacks, etc can help dispersion and still make it look like a room.
 
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plhart

Audioholic
"rugs generally absorb only a very narrow frequency band and can make things worse. Maybe a small throw rug in front of the speakers."

In writing about room acoustics, the problem I always struggle with and try to make you, our readers, aware of is that it is very hard to speak in absolutes when we talk about sound.

In acoustics, that is, once the electrical signal is "transduced" by the speaker into sound waves, the measurement of said characteristics becomes dependant on the enviroment and the device being measured. The same is true in making statements which sound like certainties, but which are, in reality, are only my or someone else's perception of what they heard, over their system, in their room.

The framework for understandstanding what we're trying to convey then, is to understand from whence it is we speak in such foreshortened formats such as this. (Boy did that sound stuffy! Hope it made a little sense.)

To Az's statement above: True. A rug without padding will affect only very high frequencies. A rug with a wool pad behind it will have an effect lower in the frequency range. The measure of how much and what frequencies are absorbed comes down to thickness of the material. Or whether or not you can make that material "appear" thicker to the sound waves by, for instance, spacing it away from the wall which is often done in recording venues. (And obviously, on a floor, that spacing trick is not practical.)

A rug will, however, change the equation of % desired absorptive material in a room (25%) vs. % diffusive material in a room (25%). And the way in which a rug works, by absorbing progressively more waves as the frequencies increase is linear enough that a standard shelving-type of control (a treble control) can suffice in restoring the highs to re-again balance the mids. (In the great majority of cases this is obviously not the problem. The problem is too much hard, reflective surface area.)

"A small throw rug in front of the speakers", unless it is positioned 1/2 way between the listener and the speakers so that the high, axial-bounce frequencies are attenuated will do little except to add to the percentage of absorption added to the room, and the cooresponding reduction of hard surfaces, subtracted.


"For behind the seating postion you want dispersion. Bookshelves, knick knacks, etc can help dispersion and "

The answer to this depends on the relative distance from the listening position to the rear wall, the type of speaker system utilized (monopole, bi-pole, di-pole) and the distance to the front speakers too. If one is very close to the rear wall then absorption is recommended directly behind the listener to attenuate slap echoes which are relatively strong and can cause loss of vocal intelligibility from the front center channel.

It is, however, often recommended that diffusors be used to the left and right sides of the listening position because they can aid greatly in promoting in a more diffusive rear soundstage by scattering 2nd order (tangential) reflections. The ear is quite sensitive to placement directly behing the head because there your two ears are both equidistant. To one side or the other though of that 180 degree location our positional acuity becomes much poorer. This is why diffusors can be so effective in these locations.
 
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N

nm2285

Senior Audioholic
"6) Treat first reflection points on side walls with sone absorption material such as cloth, drapery, etc. "

What's the best way to find the first reflection point?
 

plhart

Audioholic
What's the best way to find the first reflection point?

With a mirror. Have someone walk along the side wall moving a mirror while you sit in the listening position. When you can see your right speaker in the mirror on the right wall that's the first reflection point. Start asorptive material about 12" to 18" off the floor and run it up to about 24" above your head about that point. Absorptive panels are usually available in 2'W x 4'H sizes. 2" is the very minimum thickness. It will absorb down to about 500Hz.
 
Az B

Az B

Audioholic
PlHart has some great ideas. I was mainly responding to the WAF factor by mentioning things that she would easily accept or that would be normal items already in the room. For in depth acoustical treatment, the primer is a great start.

Good luck!
 
P

papostol

Junior Audioholic
Great stuff guys! I have curtians on the back wall which obviosly covers a large window. The listening position is right up against the window which leaves no room behind me. I will put the curtians down when doing some listening.

I have a throw rug with padding that streches from the speakers to the listening position.

It's hard to share your listening room!

Thanks Again!
 
N

nm2285

Senior Audioholic
plhart said:
What's the best way to find the first reflection point?

With a mirror. Have someone walk along the side wall moving a mirror while you sit in the listening position. When you can see your right speaker in the mirror on the right wall that's the first reflection point. Start asorptive material about 12" to 18" off the floor and run it up to about 24" above your head about that point. Absorptive panels are usually available in 2'W x 4'H sizes. 2" is the very minimum thickness. It will absorb down to about 500Hz.
Thanks for the advice. Where's the next best place for panels? Ceiling? Rear wall? Lots of cinder block in an on campus appartment so I'm doing what I can to dapen some of the sound (and luckily, the roommates don't care that I and others in this hobby are a bunch of psychos).
 
M

marius

Enthusiast
plhart said:
What's the best way to find the first reflection point?

With a mirror. Have someone walk along the side wall moving a mirror while you sit in the listening position. When you can see your right speaker in the mirror on the right wall that's the first reflection point. Start asorptive material about 12" to 18" off the floor and run it up to about 24" above your head about that point. Absorptive panels are usually available in 2'W x 4'H sizes. 2" is the very minimum thickness. It will absorb down to about 500Hz.
What if your reflection point is not there on one side wall? Say there's no wall there and it's just wide open to the kitchen or something. Does that make things better or worse?
 

plhart

Audioholic
"What if your reflection point is not there on one side wall? Say there's no wall there and it's just wide open to the kitchen or something. Does that make things better or worse?"

In this case you need only address the first reflection on the existing wall and if you have a flat 8" reflective ceiling, then the ceiling too. You're striving here for balance, clarity and size of image.

If you've got one completely open area then you're trying to make the opposite reflective wall to look identical acoustically as the open area. If either your left or right front speaker is too close to the reflective wall then the wall will become an "acoustic mirror" and increase the apparent image sizes projected from that speaker which of course messes up the system's balance, soundstage and imaging.
 

plhart

Audioholic
"Thanks for the advice. Where's the next best place for panels? Ceiling? Rear wall? Lots of cinder block in an on campus appartment so I'm doing what I can to dapen some of the sound (and luckily, the roommates don't care that I and others in this hobby are a bunch of psychos)."

Aw, to be a psycho in college once again!

Get as many yards of cheap doubleknit cloth as you can afford. It's what is used for grille cloth and works well for holding a roll of fiberglass or carpet padding or rock wool batting if you can find it. The doubleknit may come in 4' or 5' wide rolls so that's the width of your sandwich. Sew a minimum of 1" and preferably 2" material into a sandwich which you'll then drape artfully in half-rolls from the ceiling and maybe down the back wall behind your listening position. If you can, keep the back wall draping 2" or 3" away from the wall.

Let us know if they lock you up.......
 
N

nm2285

Senior Audioholic
I already purchased some acoustic foam panels (found them cheap on ebay). I mean I don't have THAT much time. I may be nuts but I still have to pass if I want to continue being nuts at the Univerity of Virginia. Of course, I guess I'd have plenty of time if I did get kicked out...

Thanks for the responses
 
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