A pic of a door with some NXT sound dampening

Can I ask, is the purpose of this to lessen the outside sound or help with the acoutics of the stereo?

 

I've been suspecting this for years... and it was confirmed by some videos by audio shop owners on youtube... you guys are using way too much of this stuff. the goal is to damp panel vibrations where there's no reinforcement. Basically wide open "plains" of sheet metal. And even then, you only need a small patch/square of it. This is evident from the way manufacturers dampen their cars. If you look at the stock Prius exterior door skin, you'll notice a 5"x5" square right smack in the middle of the door panel. Not the entire panel. Since this particular type of material really only prevents panels from vibrating, the best bet for this stuff is to damp any empty parts. That's how I did my car, I used very minimal amounts and the doors sound and feel more solid as they shut. I did not do the entire panel.

 

The more the better in my experience if you can sacrifice the weight that it adds. Spot patch will do the job for many with noticeable change in sound and road noise. Normally one patch where the speaker sits and one behind it on the inside door skin.

Btw op, you added new speaker to oem system without an aftermarket amplifier?

 

Reflectix foil insulation (home depot $15) works well, I overkill it with bedliner. better sound, better a/c & heat

 

Yes, you're on the money here. It's a mass loading damper so only really works on unsupported panels. It's useless on an inner door skin as a sealer - should use sheet plastic or similar. A great use I found was reducing heat. I has an Alfa 156 that would bake if parked up on a sunny day. A single layer of Dynamat reduced cabin heat substantially.
Having said all that, I used to go completely insane with the stuff: my old car had a 36ft2 bulk pack in each door.

 

Is the price comparable to Dynamat?