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So I think it's about time to install some Dynamat in my car. I've been putting it off for a little over 5 years now..
I have a few questions.
1) Where are the most beneficial areas to Dynamat? best for sound quality, reduce road noise, and SPL .
My thoughts are (in order) front doors, rear doors, trunk, floor, headliner, firewall
2) The front doors are pretty bad. I think this is my primary area. I'm just trying to figure out exactly how I should install it. I notice that when you take the door panel off, there is a plastic shield bolted on, then under that is the interior and exterior sheet metal of the car. my THOUGHT is that it should go between the interior sheetmetal and plastic shield. but I'm not sure.. Where exactly should I put it?
3) in the trunk, I am going to Dynamat the entire floor and I'd also like to do the inside of the trunk lid, but I don't want it to be that obvious. Should I just Dynamat what the trunk lid liner can cover?
4) do you have any tips for installing in any of the areas I mentioned?
5) Is anyone near middle tennessee and want to help?
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1) Your lineup sounds pretty good. I think I'd swap trunk and floor though. I have noticed when you drive the car without the rear seats, you can hear gas sloshing around in the gas tank. This leads me to believe quite a bit of road noise can get through here too.
3) That's what I did. If you have vibrations you're trying to stop, hunt them down and wedge something in there to prevent the vibration. But just for deadening road noise, I'd just do under the liner. Looks ugly any other way.
4) Sound deadening must always lay on metal and have no air bubbles. A roller helps, but I actually prefer a block of wood for some reason. lol Seems to work better for me.
To be clear, soundproofing requires lining everything to form an air-tight seal between the body shell and the interior, plus a lot of mass. Vibration dampening (Dynamat, Damplifier) does not require complete coverage to be effective, but does require a tight bond to the metal surface. Covering unsupported plastic or the asphault-like foam stuff already stuck to metal from the factory is also likely to make little difference.
Front doors made the most obvious difference, but I did everything else at one time, so can only speculate on the relative effectiveness of the rest. Areas near the exhaust and muffler are likely to be next most important, followed by the roof, transmission tunnel and front floors. The firewall is almost impossible to access except under the front footrest.
Doors + trunk + area under and behind the back seat cushions can be done without taking the car out of service for some time. Be sure to cover the laminated cross ('X') braces between the rear seat and plastic beauty covers - it will often rattled when thumped.
I should also mention (though it's in the service manual) that disconnecting the battery is an especially good idea when working around the airbag stuff! The right way to get the rear deck cover off (there's a DIY, but note: http://www.rx8club.com/showpost.php?...8&postcount=82 ) is to pull off the C-pillar covers which requires pulling off the rear passenger side panels. Once that is done, it's not a huge deal to pull the A-pillar covers and drop the headliner, though that's much easier to do with the front seats out. There are some tricks for pulling the headliner, so consult the service manual. With the headliner out, be sure to put a bit of sticky foam between the top of the sunroof motor and the roof - it's very close and a potential rattle generator.
Also, if you pull the carpet, you will have to remove the lower mounting bars for the front seatbelts. If they are allowed to retract fully into the holder, they won't come out again until the safety system is online again - best to put a strong spring clamp on the belts to prevent that full retraction.
Of course, pulling the carpet means pulling the center console too.