#1915122 - 03/24/08 03:06 AM
Foil side out + Acoustic Foam - needs spacing ?
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dogster
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Registered: 02/27/08
Posts: 18
Loc: Sydney, Australia
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Quick query:-
If using 50mm foil-backed rockwool/fibreglass spaced 70mm away from a brick wall, with the foil side facing into the room (to maximise low end trapping efficiency), is it feasible to attach 50mm acoustic foam directly to the foil to tame high frequencies, or should it be spaced away to allow the foil to flap about a bit ?
Thanks,
Stewart.
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#1915236 - 03/24/08 08:09 AM
Re: Foil side out + Acoustic Foam - needs spacing ?
[Re: dogster]
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Ethan Winer
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Registered: 06/12/00
Posts: 5300
Loc: New Milford, CT, USA
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I never tested that particular combination. But I'm pretty sure you'll want to mount the foam so it does not touch the facing.
--Ethan
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#1916070 - 03/25/08 01:58 PM
Re: Foil side out + Acoustic Foam - needs spacing ?
[Re: Ethan Winer]
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gullfo
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Registered: 03/30/04
Posts: 75
Loc: Old Tappan, NJ, USA
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50mm isn't doing much bass trapping... what do you perceive the value of the foil is?
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#1916140 - 03/25/08 04:52 PM
Re: Foil side out + Acoustic Foam - needs spacing ?
[Re: gullfo]
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dogster
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Loc: Sydney, Australia
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I don't know how it works, but pretty much everything I've read points to facing foil into the room to maximise bass trapping. I'm starting with 50mm rockwool with a layer of 50mm foam for the walls (spaced 70mm away from the walls), same for the ceiling except with 150mm space. I'll be putting 900mm wide rockwool/foam "sandwiches" diagonally across every wall/ceiling corner that I can, and 600mm sandwiches across all possible wall/wall corners. In the tri-corners next to the ceiling I'll be placing 600mm hollow cubes made of 100mm rockwool and then slap 50mm acoustic foam over the exposed areas for good measure. The foil facing on the wall panels is really just to try and extend the low frequency absorption as much as possible.
I'm building the whole thing on a modular frame so that a) I can add another layer of rockwool to any or all of the panels, and b) the wall and ceiling absorber panels can be converted into resonating panel traps fairly easily.
I'm hoping that any bass trapping will be taken care of by the large 100mm sandwiches across the corners though - fingers crossed.
Because my room is asymmetrical I'm starting out by making it really dead and flat as possible, then carefully place diffusion in lieu of acoustic foam to liven it up.
By the way, do you have any recommendations for a reasonably priced SPL meter ?
Cheers, Stewart.
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#1916500 - 03/26/08 10:07 AM
Re: Foil side out + Acoustic Foam - needs spacing ?
[Re: dogster]
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gullfo
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Registered: 03/30/04
Posts: 75
Loc: Old Tappan, NJ, USA
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i'm not sure i've seen documentation on how the foil improves bass trapping, it certainly can be useful for mid and high frequency preservation. the 600mm and 100mm should work, i don't know if you need the foam.
radio shack makes a nice digital meter
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#1916714 - 03/26/08 04:21 PM
Re: Foil side out + Acoustic Foam - needs spacing ?
[Re: gullfo]
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dogster
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Registered: 02/27/08
Posts: 18
Loc: Sydney, Australia
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In saying "Everything I've read" I'm referring to articles in this forum (and other forums I think), specifically Ethan's "Acoustic Treatment and Design...".
All my wall and ceiling surfaces will be covered with foil-backed rockwool so I would need something (eg foam and diffusion) to control high Hz reflections - surely ?
I can get a $50 Radio Shack SPL meter locally (looks like model number 33-4050) but it's only rated from 31.5Hz to 6KHz, with an accuracy of +/- 2dB. Is that good enough to do proper testing ?
Stewart.
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