Using craft foam sheets for box damping

[fjhuerta]

Hi all,

I was wondering how to damp a vented box - the proper way.

Buying acoustic foam from Parts Express is prohibitively expensive due to shipping costs.

I'm allergic to fiberglass, and I haven't found carpet padding the thickness I need anywhere.

But, right next to my office, there's this art supply store that sells foam sheets.They are 9mm. thick, and 0.70 cents each. Very similar to these ones: http://www.joann.com/joann/catalog.j...RODID=prd28413, only a lot thicker.

Do you think I can substitute acoustic foam for, say, 2 or 3 foam sheets (which would get me 1" of a foam barrier?).

[---k---]

I believe that it comes down to whether the foam is open cell versus closed cell. Soft pillow or mattress like foam usually works. Hard rigid foam, like styrofoam, doesn't work. That sounds like it might be a rigid closed cell foam, but I'm not sure.

[bluewizard]

Craft Foam is closed cell. So, I don't think it will work for this purpose.

First you need at least a couple of inched of material on the sides and back. One options is packing foam which I linked to in another thread.

http://www.uline.com/BL_863/Convoluted-Foam-Sets

http://www.uline.com/BL_8002/Anti-Static-Convoluted-Foam-Sets

Example,

SIX 24" x 24" charcoal colored 2 inch double sheets @ $9.95

NINE 24" x 36" charcoal colored 2 inch double sheets @ $12.45

But even that is not quite thick enough.

You can also use polyester batting typically used for seat cushions and quilts. This can be found at fabric stores.

Also, be aware that they now make house insulation out of old recycled cotton cloth. Sometime made out of old blue jeans. The cloth has been made flame retardant, and is available in roles just like fiberglass insulation. It is completely non-toxic, non-itchy, and most likely hypo-allergenic.

In my latest project I used 2" of soft fiberglass then covered that with a 1/2' of polyester batting. That way if I ever have to work on those speakers again, I don't have to worry about the itchy fiberglass as that is all covered by soft itch-free poly.

You can also use upholstery foam which can be purchased at fabric stores but it is not that cheap.

I think in your case the lowest price might be 1/2" of polyester on five sides, then covered with the 2" of convoluted packing foam linked to above. Keep in mind that the sheet are double interlocking sheets. So if it says 12" x 12" x 2", you get two sheets that are 12" x 12" by close to 2"; double interlocking sheets.

I've purchased from Uline before and they don't have a problem with small orders to general consumers.

Steve/bluewizard

[Hdale85]

If you can't find anything else you can look for rockwool insultation or if all else fails just grab some of the egg foam bed pads.

[fjhuerta]

Thanks for all your comments. I found a place where I can get custom foam made in any profile I want. I bought 8 square meters for $80 of the highest density open cell foam I could find, with an eggcrate profile.

Let's see how that works out...

[Silver1omo]

Thanks for all your comments. I found a place where I can get custom foam made in any profile I want. I bought 8 square meters for $80 of the highest density open cell foam I could find, with an eggcrate profile.

Let's see how that works out...

Do you know if that place is still in business? Do you have any contact info?

Thanks!