[jtwrace]

I have two doors that are in my listening room.  The back of them are to the outside of the house.  What can I use on the back of them that would damp them? 

I'd love to use a really good CLD.

[bpape]

Green Glue and a sheet of MDF work great.

[jtwrace]

Green Glue and a sheet of MDF work great.

Really?  1/2" or 3/4"?

[bpape]

More mass is your friend (as long as the hinges will take the additional weight...)

The only problem with MDF and being outside is that you're going to have to seal it somehow to deal with the weather - though that's something you'd have to do with pretty much any material.

[jtwrace]

this is interesting stuff http://www.megasorber.com/solutions/building.html

A bit far away though.

[WGH]

I would shy away from MDF, it has a great affinity for moisture and puff up and flake off if it ever gets damp which will eventually happen in an exterior application. Durock (cement board) is dense and very water resistant. Add a layer of sound damping or green glue, patch the screw holes with Bondo and paint.

Wayne

[bpape]

Probably a better suggestion with the cement board.  That will be much less prone to the weather.

Bryan

[audioblazer]

I tried green glue and MDF ( 2 layers) . Didn't really work unless you take care of the gaps between the door and door frame

[WGH]

Proper gaskets are always needed to keep sound out or in. I use Pemko all the time, they have an extensive lineup of products.
http://www.pemko.com/

Pemko's New Hospitality Products
Watch the video: http://www.pemko.com/index.cfm?event=videoLibrary.listVdeos
Description: Pemko introduces a new line of door hardware and gasketing products designed for noise and light reduction!

[jtwrace]

Would some Pink foam insulation with some green glue do anything other then provide some needed insulation?

[bpape]

Not really.  The idea is to add additional mass - which the foam doesn't do.  The Green Glue is also designed to work between 2 layers of mass.

Bryan