Sound deadening coating

[ben62670]

Well I have a rather large set of speakers that I am working on. They have about 100sq feet of interior surface. I was looking for a long time for sound deadening material, and finally went to Lowe's. I read the labels on all the cans of various coatings. One of my major concerns was having any product with high VOCs in them. I don't want drivers to come unglued do to fumes. I chose rubberized latex driveway sealer after doing a lot of reading of labels. I dipped a piece of MDF in the stuff. I left it on as heavy as I could to try to get it to fail by peeling or cracking. After 2 days of drying I was able to scrap the coating off the MDF. It does bond well, but I used a bit of elbow grease to get it off. I wanted to see if there was any problem with wood swelling or softening. No problems. Second test. Picked up a hammer, and struck both ends of the MDF. There was a definite ring to the end with no coating, and the treated end sounded nice and dead. The cost of a 5 gal bucket was $25! works great. I applied a thin coat today as a tack coat. I have painted for many years, and know to put on a thin coat at first, then build up the fallowing coats.

Here is a link to my project.

http://www.polkaudio.com/forums/showthread.php?t=53273

You have to do some scrolling to see the progress pictures, but I believe it is worth a read, and I like to get feed back on my ideas.

Thanks Ben

[ben62670]

66 views, and not one reply?
Has anyone ever tried this approach?

[sbrads]

I haven't tried it in speaker cabinets but if it's like the stuff used to reseal flat roofs I've used it quite a bit for its intended purpose. It's water based and definitely doesn't give off fumes and yet it dries to a rubber-like substance, so yes it could be useful for cabinet damping.

If I was taking on a DIY speaker project I would try something like that, or try to find something that sets to rubber in the absence of air so that I could lay panels of hardboard on top, that ought to damp really well.

[Colin]

Looks a very ambitious project. You might find the original BBC research papers on cabinet damping interesting, if you've not already encountered them. The main one is here. A Google for Harwood and Loudspeakers will turn up more.

[ben62670]

Thanks for the link. I have turned into an audio junkie about six months ago. I spend an average of 3 hours a night on reading!
Ben

[Colin]

The article covers a range of materials for loudspeaker cabinets. One of the many interesting points it discovered is that doubling cabinet wall thickness has relatively little effect on wall resonance - you just have to use twice as much damping material.

Good luck with the rest of the reading - there is some good stuff out there. Some of the classic loudspeaker books from the 50s and 60s have hardly dated and contain priceless material.

[ben62670]

I have David Weems book on loud speakers design. The main reason I posted this is many people are buying very expensive acoustic dampening material. I bought the rubberized latex driveway sealer for $25 for 5 gallons. It works great. I dipped a piece of MDF in the bucket fully knowing that heavy first coats typically fail either by cracking or peeling. To my surprise I did not have either issue with the test piece. I hit the treated end with a hammer, and I heard thud thud. I hit the other end of the MDF, and I heard a distinct ring. I have had quite a bit of help here electronically. I just wanted to share this with you guys. I highly recommend if you are using any sort of coating to apply a light "tack coat" first, and then build it up. The last coat I used as the adhesive for the poly batting. It worked out fantastic.

Ben