quisterio

Alright, since im about to get subs installed soon, I got to thinking about unwanted vibrations and where they can come from.

The plastic trim in the hatch area on the left and right sides, would it be worth filling those areas up with polyfill?

Im talking about taking them off and totally stuffing them with it.

Would it just be a waste of time or actually help with vibrations?

Gummie

Polyfill won't kill vibrations - you need a mat or a thick liquid based deadener to do that. The most commercially available option is Dynamat but you're really just paying for the marketing with it. There's no need to pay that much for a product that you can get elsewhere for much less and generally also of better quality.

There are 3 primary deadeners available for cars. They are:

Butyl /asphalt based mat. Butyl is a better choice than asphalt because it's more durable and sticks in place better than asphalt based products. It’s only marginally more expensive than asphalt and that added cost is usually made up for with thicker overall mat. Mat kills vibrations by adding mass to whatever it’s applied to and will help shield your car against lower frequency sound. It works under the same principal as sticking your hand against something that’s vibrating to stop it from vibrating. Will it stop higher frequency sound? Yes, but not as well as other options, which brings me to the next item.

Closed cell foam. This is the stuff you see in recording studios hanging off the walls in the funky pyramids. It's excellent at absorbing mid/high frequency sound but really isn't that useful in terms of lower frequency sound because of the relative thinness available for car applications. I’ve never used the stuff so I can’t vouch for it but I can say that I plan on installing it in my car once I get closer to putting my interior back together.

There's also a liquid deadener. It works on the same premise as mat - killing off vibrations and thus lower frequency sound but it's a TON easier to apply. Take it from me, I've done work with both mat and liquid deadener and the liquid can be applied in a fraction of the time.

Here are some companies you can buy from

Second Skin – They sell all of the above and are a good/reputable company. $2.34 per square foot if you buy 80 square feet. $2.76 if you buy 10. More varying pricing in between depending on quantity.

Raammat – My personal favorite (only because I’m using their butyl deadener in my car – this was pre-ED’s offering). Their material costs $1.90 per square foot and you’ve got to buy a full roll of the stuff if you want any at all (62.5 square feet). They also sell closed cell foam but don’t sell a liquid deadener.

[url=http://www.edesignaudio.com/edv2/index.php?cPath=24] – They sell everything (foam, mat, liquid) just like second skin and they also offer varying thickness of mat. You can purchase 45 mils thick mat ($1.00 per square foot) or .60 mills thick mat ($1.60 per square foot) depending on your wants/needs. This makes their offering the cheapest out of those listed.

Honestly though, I've got a pretty crazy substage and there are no vibrations to speak of inside the car. The deadening has helped a good deal with the exhaust as well as some road noise (it sounds like I have a fiberglass roof when it rains) but it hasn't made that noticeable of an impact on sound.