Automotive Sound Deadener Showdown

[mah]

This comparison may interest Altec Users.

Cheers, MarshallSound Deadeners Showdown

[bfish]

Some time ago I did "due diligence" in searching out damping products. For years, Aquaplas was the Altec/Lansing de facto standard, one of many wartime developements that found later industry uses. It hasn't been made in years, but the current replacement product, called AntiVibe is available through Blanchard (Canada) in 55 gal drums. Prepare to see your banker before purchase.

It soon became apparent to me that the cost/profit ratio of such products became astronomical as soon as they got the "audio/acoustical" purpose label. That's a polite way of saying "prepare to bend over and spread 'em". There are, however, ~equivalent products targeted at other markets that are both effective and affordable.

For brush-on/spray application, The best bargain I found was at WW Grainger;

http://www.grainger.com/Grainger/wwg...ration+damping

For blanket application, there's a much cheaper alternative hiding on the Home Depot shelves;

http://www.homedepot.com/webapp/wcs/...3+90401+500209

Both products are intended for HVAC ductwork sound attenuation, an industry that lacks the glamour and golf-playing, pool-party conmen that sell audio products. If you're into the brand name thing and are willing to support some profiteers' vices, polish up the VISA.

There may be other affordable options, but my needs and budget were satisfied by the above, so I quit looking for more.

[mah]

G'day bfish,

Thanks for your input. I will check out similar kinds of suppliers in Oz.

[Old Guy]

The stuff you mention at Grainger is good, have been using it for a while. Made by a company called INC, I think that's Industrial noise control. I buy from a place called Drillspot, they handle other products from the same company, you can get bulk materials like automotive sound deadener but cheaper. YMMV.

[aauwen]

I've heard that the spray on truck bed liner is the same, or similar, to the Aquaplas used on Altec 311-90 horns. If this is true, I have found a local company that is willing to spray a horn when they are spraying a truck bed. Does this sound something I should look at doing?

[bfish]

Hi Joe,

Bedliner is only "similar" to Aquaplas in that it's a spray-on coating, just like ketsup and mustard are both squirt-on condiments. In no sense is it optimized for acoustical damping. If you need to treat your horns for abrasion resistance or non-skid footing, spray them with bedliner. Otherwise...

Spray or brush on acoustic damping compounds utilize a very high solids content (typically in the form of tiny mica platelets) suspended in a viscoelastic polymer to dissipate vibrational energy. As the surface it's applied to vibrates, the material flexes, causing the platelets to rub against each other, converting the mechanical energy to heat through friction.

<font color="#FFFFFF" size="1">[ September 29, 2008 12:57 AM: Message edited by: bfish ]</font>

[GM]

True, but as I noted/implied WRT spray undercoating in the other thread, if you spray it on thick enough to mass load it enough to push the horn's Fs to below its pass-band, then there's nothing to excite it. This is essentially what sand loaded paint does, but don't have a clue how many passes of spray bed liner it would take to do it or even if you can layer it on really thick without it cracking/whatever.

Only one way to know for sure, I guess.

GM

<font color="#FFFFFF" size="1">[ September 28, 2008 04:32 PM: Message edited by: GM ]</font>

[Audio_by_Goodwill]

Originally posted by GM:
True, but as I noted/implied WRT spray undercoating in the other thread, if you spray it on thick enough to mass load it enough to push the horn's Fs to below its pass-band, then there's nothing to excite it. This is essentially what sand loaded paint does, but don't have a clue how many passes of spray bed liner it would take to do it or even if you can layer it on really thick without it cracking/whatever.

Only one way to know for sure, I guess.

<font size="2" face="Verdana, Helvetica, sans-serif">Spraying the bedliner on thick enough shouldn't be a problem. It's been awhile since I've researched it (for bed use, not audio), but I seem to recall it being put down about 3/8ths to 1/2 inch thick in some areas. Having said that, I was under the impression that it didn't work very well for audio.... too stiff/rigid. I don't know where I read that, Though..... maybe here, maybe Audiokarma?

[bfish]

GM's right again. My explanation assumed ~equal application thickness. In the original application (aircraft), and the current intended use (ductwork and other lightweight noisy panels), mass loading simply isn't a practical option. My main point was to disprove the myth that bedliner was in any way similar to damping compounds.

[GM]

Right on, for least weight/max damping you want constrained layer construction, i.e a high impedance mismatch between layers.

BTW, by thick, I'm thinking in terms of inches, i.e. turning it into a blob, same as I had done to a pair back in the '60s by a paint contractor shooting something like this on the inside of industrial corrugated roofing: http://www.hytechsales.com/prod150.html

GM