is this sponge as good as acoustic sponge? - AVS Forum
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post #1 of 9 Old 07-20-2013, 08:59 AM - Thread Starter
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is this bedding sponge as good as acoustic sponge?

I stuffed a couple pillows behind the main speakers an heard a slite improvement.

I would like to have a few acoutic panels directly behind the main LRC speakers then the first reflection points on side walls my right front main speaker is a tad close to the right wall approsmently 10" I would like sponge on this side wall to prevent reflections.

I plan a QRD type diffuser on the back wall surrounded w/ the same sponge.

http://www.walmart.com/ip/La-Z-Boy-BigSleep-3-Convoluted-Foam-Topper/22991618?findingMethod=rr#rr


I would prefer to use sponge instead of stuff like fiberglass or Roxul rockwool (don't want to be itching and breating fiberglass). plus the exposed sponge looks kindof cool.

I'm kindof leaning toward this walmart sponge because it's white (unlike 99% of actualle acoutisc sponge) it's inexpensive and it's thick.

any tips is appreciated.
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post #2 of 9 Old 07-20-2013, 12:14 PM
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Originally Posted by stevethebrain View Post

is this bedding sponge as good as acoustic sponge?

No.

That was easy!

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post #3 of 9 Old 07-23-2013, 06:47 AM - Thread Starter
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not much of a answer care to explain you'r self since you are the expert.

I'm thinking sponge is sponge.

 

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post #4 of 9 Old 07-23-2013, 08:14 AM
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All foam products don't possess the same acoustic absorption characteristics. Well executed velocity type absorbers, do a better job at converting acoustical energy into heat. Some do it better than others by design. The mattress pad is just that, ... a mattress pad.

You're right, the look may be appealing, but if one wants to absorb energy with foam, the big dips in the corrugated pattern aren't helpful. The absorber needs as much material thickness as possible.

If you're averse to the itching, there's products that address that. If you have respiratory concerns, there's simple answers to mitigate your concerns.

Bottom line, the corrugated mattress pads are essentially too thin to be significantly helpful. There's other DIY methods/materials that are much more effective, and equally as budget minded. Granted, many foam products do look appealing. But they're not effective enough in the frequency range where it's needed. They would likely only remove the higher freqs, leaving a dull and lifeless characteristic to the playback.


Good luck

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post #5 of 9 Old 07-23-2013, 11:22 AM
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Originally Posted by stevethebrain View Post

not much of a answer care to explain you'r self since you are the expert. I'm thinking sponge is sponge.

You didn't ask why, only if. biggrin.gif

FOH gave you the right answer, and I can add a bit more: Acoustic foam is called "open cell" because the pores go deeply into the material. As sound waves travel into those holes the energy is converted to heat. Non-acoustic foam - bedding foam, packing foam, etc - is "closed cell" and the holes stay near the surface.

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post #6 of 9 Old 07-23-2013, 03:34 PM
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Ethan is right on point about the pores in acoustic foam and how the energy converts. However, being non-acoustic doesn't necessarily make a foam closed-cell, and most every seat cushion or bedding foam material is open-cell (memory foam included), as is squishy charcoal packaging foam. There are a handful of things that make acoustic foam perform differently than standard open-cell, however; a couple being unique firmness and density combinations, and finer cellular structures. Comfort and support foam like you'd find in a couch cushion usually has a Pores Per Inch (PPI) rating of 60-70 cells, with some extra-porous varieties like filter foam or fast-drying outdoor varieties as low as 25 or 30 PPI. Good acoustical foam possesses a PPI around 80. A higher PPI means more cells, which translates to more opportunities to convert energy. A 12” x 12” x 3” tile of 80 PPI foam would roughly have about 127 million more cells than a 60 PPI foam, for example.

The picture below is a close-up of gym rubber, which is a closed-cell foam usually seen as floor padding. You can see how each cell terminates with a cell wall. When uncut, each cell is like a tiny, sealed bubble.


This picture is a close-up of open-cell. It isn't acoustic foam, but you can see in the circled area how the material has a wiry, reticulated structure that is completely interconnected. This structure is more pronounced on this particular foam than it is on acoustic foam, but it's kind of hard to get a good shot of these little cells, so this is just a general example biggrin.gif


But I digress. To backtrack to your original question STB, bedding foam isn't going to function as well as acoustic foam, which is specially made to serve an acoustical purpose, in addition to most varieties being treated to be fire re.tardant, which is an important safety consideration as well.
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post #7 of 9 Old 07-24-2013, 12:04 PM
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Good info Carlo, thanks for sharing.

We've got a foam king sized memory foam mattress that's progressing toward the end of it's useful life. It's a Sam's Club knock off of the typical premium brand offerings. We really enjoy it and it was a fraction of the price of the real-deal. However, upon time to get a new one, I plan on testing this un-wieldy thing for it's acoustic absorption usefulness, ... in a real room. At least that's the plan, sounds good now .. rolleyes.gif

I've always enjoyed the foambymail web-site. The new foam sacks appear interesting. A few of those in the middle of one's room would seemingly offer a modicum of LF damping. Our youngest lives on the family room HT floor, .. so that'd be a perfect application,... thinking...

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post #8 of 9 Old 07-24-2013, 02:23 PM
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Quote:
Originally Posted by FOH View Post

Good info Carlo, thanks for sharing.

We've got a foam king sized memory foam mattress that's progressing toward the end of it's useful life. It's a Sam's Club knock off of the typical premium brand offerings. We really enjoy it and it was a fraction of the price of the real-deal. However, upon time to get a new one, I plan on testing this un-wieldy thing for it's acoustic absorption usefulness, ... in a real room. At least that's the plan, sounds good now .. rolleyes.gif

I've always enjoyed the foambymail web-site. The new foam sacks appear interesting. A few of those in the middle of one's room would seemingly offer a modicum of LF damping. Our youngest lives on the family room HT floor, .. so that'd be a perfect application,... thinking...

If the acoustic test's don't go so well, you can still leave it on the wall and literally "bounce off the walls" having fun ! doh
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post #9 of 9 Old 07-25-2013, 11:03 AM
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Quote:
Originally Posted by FOH View Post

Good info Carlo, thanks for sharing.

We've got a foam king sized memory foam mattress that's progressing toward the end of it's useful life. It's a Sam's Club knock off of the typical premium brand offerings. We really enjoy it and it was a fraction of the price of the real-deal. However, upon time to get a new one, I plan on testing this un-wieldy thing for it's acoustic absorption usefulness, ... in a real room. At least that's the plan, sounds good now .. rolleyes.gif

I've always enjoyed the foambymail web-site. The new foam sacks appear interesting. A few of those in the middle of one's room would seemingly offer a modicum of LF damping. Our youngest lives on the family room HT floor, .. so that'd be a perfect application,... thinking...

Glad it helped! While that mattress isn’t going to be something that blows you out of the water and leaves you wondering why you ever slept on it instead of treating a room with it, it would have some impact in the high-frequency/reflection area. The performance and performance spectrum isn’t going to match something made from acoustically-formulated foam or insulation-based traps, but mass is mass is mass. If it helps or hurts your current situation, that is left to be seen, but for the low price of FREE, giving it a whirl can’t hurt, even just for the sake of learning about your room.

As for our Foam Sacks, I can’t say we’ve ever thought about them acoustically, but I wouldn’t be surprised to see them cause a significant drop in CFE - Child-Frequency Energy! (Just a joke biggrin.gif)
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