What best Bitumen to use in a sandwhich?

[bzdang]

I read somewhere here about hardwood flooring underlayment (can't remember where), so I recently purchased a roll of it at home depot. Of course I threw out the packaging so I can't tell you exactly what it is, but it is a distinctive light green and is reasonably priced. It might do for a sandwich using contact adhesive or 3m 77 spray adhesive. It's 2mm thick and visco-elastic. I have a lifetime supply now, so e-mail me if you wish and I'll mail you a piece to try out.

 

[GM]

In this case he's referring to organic felt mat saturated with an asphalt compound..

No, I wasn't, see my recent post. What you're describing is referred to as tar paper in my 'neck of the woods'. That said, three layers of it works well in a 'sandwich' in cabs that aren't subject to strong output, such as a boofshelf sized speaker, as long as a few randomly spaced screws are used to hold it all together.

I read somewhere here about hardwood flooring underlayment

Way too thin to be of use below 100s of Hz. It's basically an anti-squeak device to somewhat isolate the hardwood's and subflooring's different rates of expansion/contraction. The non-hardening glue I mentioned previously is used between the subflooring and floor joists to complete the system.

GM

 

[Sherman]

I wish to try making a composite consisting of 3/4" MDF on the outside with a layer of Bitumen and then a 1/2" sheet of cement board on the inside for speaker cabinet wall construction. ... looking at the roofing tars and driveway fillers/sealers... wondering what might be a suitable filler that will not run away in a mess after laminating and will provide the viscous damping needed. ...

How about using a product designed specifically for preventing sound transmission and decoupling?

http://www.soundprooffoam.com/?OVRAW=sound proofing&OVKEY=sound proofing&OVMTC=standard

Another idea- line the inside with 1/8" closed cell foam available from most craft supply stores. Glue it to the inside surfaces. It will act as a "decoupler". Then use your cement board inside that, glued to the foam. You'll get excellent separation for the inner box and outer box.

One more idea- use the closed cell foam as above and instead of cement board use either sheet vinyl flooring or stick-on vinyl floor tiles inside. Much lighter weight and you still decouple the inside from the outside.

If you use vinyl sheet flooring you could also ripple the sheet inside to eliminate any parallel surfaces, though it might make computing volume more of a challenge.

 

[Puggie]

Just a thought but I've been doing car audio for years and some of us spend silly money of sound deadening products. These include bitumin and viscoelastic based self adhesive sheets and visco elastic latex based 'paint' which can be painted onto wooden pannels to help reduce vibrations and also seal the interior of you box nicely, some of these are water based latex solution so no chance of any nast fumes that could harm drivers and rubber surround etc while it cures.

try this link for one companies examples

http://www.edesignaudio.com/edead.htm

 

[FrankWW]

Roll roofing.

I dunno, GM. I'm talking about this stuff without the mineral finish:

http://www.ebuild.com/guide/products/specifierResults.asp?catCode=109

I don't have fond memories of using it.

 

[GM]

Yes, that's the roll roofing I'm referring to. Seems I'm behind the times, it's rated 55lbs now. Anyway, it worked quite well for me as the filler in a plywood 'sandwich'. Theoretically it wouldn't do well between lower MOE materials such as MDF due to the impedance mismatch wouldn't be all that great, but I never tried it so YMMV.

GM