Will these work as sound insulation? [Archive] - Audio & Video Forums

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GMichael
10-09-2007, 10:46 AM
I know that these will not absorb any base, but will they help for high end absorption? It seems like these http://www.uline.com/ProductDetail.asp?model=S-6438&ref=863 at $10 will give you more surface area than these: http://www.truesoundcontrol.com/products/RDSTD36.html at $139.00.

kexodusc
10-09-2007, 01:12 PM
GM, while it's true you may get more surface area coverage, I don't know if I'd recommend them for absorption panels.
Absorbing the highs is usually not a very productive thing to do by itself for home theater/stereo use. It's doubtful you have a completely reflective room with such dreadful slap echo or flutter that just needs high frequency absorption. The high frequencies tend to be less problematic in most homes, and stuffing those out without treating the midrange is a bad combo in my experience.

People tend to look at foam and think it's all the same. Funny thing about polyurethane - it's used to make acoustic foam and bowling balls. Very different properties. I would suggest getting decent uniform absorption at critical locations instead of just aiming for surface area coverage.

Foam isn't the best value for that IMO, but it's probably the easiest to put up. It's decent for some midrange and high frequency absorption, and if thick enough, can be adequate for bass treatment too, but that stuff gets expensive. I had a bunch of burgundy foam panels from the likes of Auralex and Sonotec, and some cheap stuff from a foam producer that was noticeably inferior but still did a decent job for the money. For highs/mids and reflection treatment generic foam is probably the cheapest easiest way to go.
However, the fiberglass panels made a profound difference, and even if I had to buy them pre-made, dollar for dollar they'd have been a more effective treatment than the foam IMO, even if I ended up with less surface area treated overall.

Not sure if this stuff is fire proof either...if that's important.

GMichael
10-09-2007, 01:22 PM
So something like these then? http://forums.audioholics.com/forums/showthread.php?t=35868

I was thinking 2'x4'x6" behind each speaker, and then a few 2'x2'x4" at first reflection points.
Would I still need something for the corners?

kexodusc
10-09-2007, 03:12 PM
So something like these then? http://forums.audioholics.com/forums/showthread.php?t=35868

I was thinking 2'x4'x6" behind each speaker, and then a few 2'x2'x4" at first reflection points.
Would I still need something for the corners?
Hey that guy pretty much did what I did. I wrapped mine in some thin poly batting just to keep the nasty fiberglass locked in but otherwise pretty much the same concept.
Mine look like LJ's as I recall.

6" IMO is overkill for acoustic panels other than bass treatment...especially against a wall behind speakers. You might do 6" thick across a corner though, maybe that's what you mean, GM?
4" is plenty for bass if you get the right stuff. You're better off getting a more bass absorbing material than adding thickness - OC705 instead of 703. More cost effective at those frequencies.

For reflections, 4" is probably overkill- your goal there is to tame reflections and provide some uniform absorption - you accomplish that and then some with 2" of good quality mineral wool or rigid fiberglass. We're talking the difference between a .92 and .95 absorption coefficient for example - there's a point of diminishing returns. Some people do even 1" and report good results. The idea there being that along the side walls, ceiling, and rear wall, the midrange/lower frequencies are a bit less intense as they move further into the room. For the price difference, 2" is a nice compromise though, might as well.

A neat trick - if you can hang your panels such that they're an inch or two off the wall, or across a corner, you actually absorb more sound than just placing it on a wall. Some people build their panels 3-4" thick and only use 2" thick insulation to achieve that effect.

Those kinds of panels work (and look) a lot better than the Auralex/Sonotec stuff IMO.