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Acoustic treatment with slats - before-and-after measurements

Blumlein 88

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I don’t really need the benefits of diffusion with those slat absorbers. The slats are just for the looks.
But I don’t want the slats to have any negative effects on mids/highs.
Their main purpose should be bass absorption
Bass absorption to any meaningful amount requires depth. That is just the physics of it.
 

juliangst

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Bass absorption to any meaningful amount requires depth. That is just the physics of it.
I’ll put about 40-60cm of glass wool behind the slats. That should do the trick
 

Flaesh

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60cm of glass wool behind the slats, and w\o felt and w\o slats: arbitrary felt thickness and GFR values and simplified model:
1678639800683.png

Increasing gas flow resistance of the felt layer will worsen the result. Also, the model does not take into account the membrane effect.
 
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juliangst

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sarumbear

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sarumbear

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60cm of glass wool behind the slats, and w\o felt and w\o slats: arbitrary felt thickness and GFR values and simplified model:
View attachment 271226
I want to remind the reader to pay attention to the depth of glass wool behind the slats: 60cm. On a typical small listening room of 20m2 that will cause almost a 30% floor area reduction. Imagine the OP installing wall-to-wall cupboards on both walls!

Do you think this is a realistic solution?
 

juliangst

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I want to remind the reader to pay attention to the depth of glass wool behind the slats: 60cm. On a typical small listening room of 20m2 that will cause almost a 30% floor area reduction. Imagine the OP installing wall-to-wall cupboards on both walls!

Do you think this is a realistic solution?
For his space it is indeed a bit much.
I personally don’t need much storage space so it would be a viable solution.
 

sarumbear

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For his space it is indeed a bit much.
I personally don’t need much storage space so it would be a viable solution.
How big is your room?
 

sarumbear

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About 6x5m
So you are happy with a floor area reduction if 20%? In other words to use absorbers that will occupy 6m2 of your 30m2 floor area?
 

juliangst

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May be it is.. Practical results are interesting.
I don't know how breathable this felt is.
The main problem is finding a good coverage material for the insulation material.

I thought of getting cheap 3mm felt but it’s hard to get resistivity values for it.
Fabric will probably not look as clean as something more rigid like felt
 

juliangst

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So you are happy with a floor area reduction if 20%? In other words to use absorbers that will occupy 6m2 of your 30m2 floor area?
With glasswool I would more likely do 40cm of depth. For 60cm something less dense is better but all materials I found with this property are way more expensive than simple glass wool.

But yes, I would be fine with 40cm less room if the wall ends up looking good
 

Inner Space

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60cm of glass wool behind the slats, and w\o felt and w\o slats: arbitrary felt thickness and GFR values and simplified model:
View attachment 271226
Increasing gas flow resistance of the felt layer will worsen the result. Also, the model does not take into account the membrane effect.
I have a question about simulations like these - could you help? Allard & Champoux's 1992 equations have, I believe, proved themselves pretty accurate via empirical tests. But are they not based on a simple one-time pass-through calculation, i.e. SPL in on one side, minus SPL out on the other? But for room acoustics, aren't we dealing with three separate stages? I.e., SPL into the absorber, then some leakage through the wall, and then the remaining reflection passing through the absorber again, in the reverse direction. Can anyone elucidate?
 

sarumbear

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With glasswool I would more likely do 40cm of depth. For 60cm something less dense is better but all materials I found with this property are way more expensive than simple glass wool.

But yes, I would be fine with 40cm less room if the wall ends up looking good
I don’t see how the look of the wall is to do with the depth of the absorber…
 

sarumbear

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The better question is ''Is there are a better solution''. And I honestly don't know.
Of course there is!

Membrane, Diaphragm & Helmholtz is much more efficient than using simple absorbent materials. No acoustician will even consider using a 60cm deep absorbent wall. On a usual size room the volume of just one of such an absorber will be around 9 m3 or a volume to store 9 metric tons of water!
 
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Thomas_A

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Why not use perforated board?

 
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