transsam

iTrader: (5)

I am doing everything I can to deaden every possible sound in my car from the outside - from insulations under the carpet and on the walls and even sound proofing film on the windows.

I hope everyone on here knows that unless you plan on having passengers in the back, there is more harm than good done by keeping the rear speakers. I am looking for advice on filling the outer section of the rear panel with spray foam sound deadening like is used in houses.

Is there a downside to this?
Thoughts?

Black_Z28

iTrader: (1)

I'd like to know why you think this? The speakers in the sail panels are mid bass, which produce very little highs. So, obviously they produce more bass, which won't matter at all where the location is, to a point.

wssix99

iTrader: (5)

There are foams that you can use to do this, but they are not available over the counter. The stuff you get in stores will cause so much pressure as it expands that it will rip your steel panels and spot welds apart. (This would be a very bad thing.)

transsam

iTrader: (5)

Z-
This isn't a stock system. My fronts (it's a T/A) are CDT components rated to 300 watts/RMS/side. The bass is just an Alpine typeR, but when he wrote L'arlesienne, I doubt Bizet could have imagined 600 watts RMS!
So, if you need mid bass from the, err, mid speakers, you are dead on and my blanket statement was pretty dumb.

99-
Damn. That is exactly what I was afraid of. Thanks for the info. For ***** and giggles, I think I'll fill it with towels. I'm already in $550 on deadening, what's a bunch of towels going to cost from walmart on clearance. If it doesn't do anything, I'm only out $30-$40 more. Besides, it's like side airbags! Side towelbags?

Thanks guys.

scj

iTrader: (89)

There's no way. i've used expanding spray in foam on the interior of my car, on the armrest area bar for the rear seats, the seat brackets that stick out of the floor, as well as in various other places, and Its by no means strong enough to do this.

wssix99

iTrader: (5)

If you put a shitload of it in to a large cavity like the one behind the B pillars, you will have a much greater amount of foam expanding, which will cause a lot more force than you experienced with those smaller areas. The force would be proportional to the depth of the cavity you are filling.

This is even a problem when using the stuff for its intended purpose in a structure. You need to have an expansion relief to release the pressure.

So, you could probably drill a bunch of holes in the interior panel to let the foam escape and relieve pressure. Not sure what that would do to the car, though.

There is a special type of low expansion foam for windows and doors (you can NOT get this at a hardware store) that would be better - but even this will cause problems. (The regular foam around doors and windows will deform the jams so they don't work correctly.) The low expansion foam will probably not cause the panels to explode, but it will probably cause them to bulge a bit and deform the shape of the car somewhat. (All expansion foams will build up pressure.)

If you want to deaden the space, I'd suggest using a loose fill insulation. (Like the type blown in attics.) That will fill up the space, deaden sound, and will not cause any pressure problems. You'd just need to find a type that won't rot when exposed to moisture, etc.

transsam

iTrader: (5)

See, loose insulation, like my towelbags. Safety and insulation! I don't want to risk filling it. There is always a chance that I'll want a pair of 8" CDTs in the sail and possibly a better sub to take on only low bass. Who knows. And my towelbags are removable! I'll have layers of sound deadening there anyway, so this is really the tipping point just past sanity into overkill anyway! But if I change my sig, you can bet towelbags will be in it to confuse the hell out of people!
Thanks guys!

wssix99

iTrader: (5)

If you have time to kill, you might check out the Monster Garage Swamp Buggy episode. They used foam on that car - but were making special floats, I think.