& I can tell you if you're going to be putting it inside your rear quarter panels, it will make a big difference at first .. I especially like the bassy thump when you tap on the rear panel from the outside
However, with Dynamat by itself, it's only going to amplify the noise back into the cabin, especially if you leave the service holes of the rear panels uncovered, so all the noise in the rear wheel arches is going to create an echo back there..
To get total sound deadening, you're going to have to fill the panels with something .. I got a whole bunch of offcut foam from Clark Rubber & packed it into the rear quarter panels as densely as I could (inside pillow cases) & the results after this are much better..
I think you will get better results from using an expanding foam in the rear panels rather than using lead sheets ..
It's also cheaper, you can pick up a can of it from BUnnings or Home Hardware for as little as $8 .. I recommend for you not to get the 3x expanding stuff, you will get better results with 2x expanding foam if you can find it, its a lot denser. - Ask for "Space Invader" brand - apparently its the best stuff for use in cars.
LIke I8A4RE said, rattling is caused by the vibration between panels .. Dynamat will lessen the vibration of the metal panels .. but you need to stop them from moving altogether .. that's where the expanding foam comes in .. it will adhere to the inner & outer skin of the car & when it dries, it sets hard & especially when you have subs, the foam holds the panels in place. The way it works is when the inner or outer skin tries to push outwards with the the expanding foam pulls against it & so on .. It also acts as an accoustic barrier, because you have an added wall of sound insulation.
THe down side - is that its not really possible to remove the stuff. So make sure you get a good quality brand that doesn't deteriorate over time, or when exposed to moisture.
If you're looking for that bit of extra sound deadening for inside the cabin & you can't be bothered going to the lengths of Dynamatting *everything* like i did (I literally have done 'everything' including inside the dash)
You should be able to pick up some carpet underlay, not the springy foam stuff, but the stuff made up of all the strands of fibre, it has a proper name, but I can't remember right now .. go to a carpet store & ask for some cheapo / freebie stuff if they have it laying around..
Also, you can't just stop at the interior of your car to stop the rattles, even with the entire interior of my car out, most of the rattles come from outisde the car .. next on my list if, sound deadening the outside of wheel arches, any external plastic panels / bumpers & the rest of the mechanical knocks..
So far Ive spent about $700-800 to get rid of them.. but would be more like $500-600 if I'd gotten the Dynamat on ebay from the start - it's about $245 for a BIG Bulk Pack. CHEAP AS!
