[968kid]

The thick plastic door liner, what is/are it's function(s)
If installing dynamat do you retain this liner?
What affect does the liner have on the sound waves emanating from the speakers.
Does the dynamat affect reflective sound or the vibration of the sound through the sheet-metal of the door.

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[Darryl]

The plastic liner is the moisture barrier and should remain "mostly" intact whenever possible. Most cars have them and most people ignore them and is a very common cause of leaks.

The dynamat provides a number of acoustical benefits. It's main purpose is to reduce the outside noise from coming into the car - basic sound insulation - thus hearing more sound and less noise, increasing your "signal to noise" ratio. It can also help reduce/absorb the undesired resonant frequencies as sound bounces around and reflects off the hard surfaces of speaker cavity, in this case, the car door.

- Darryl

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[flash]

to answer the reflective/absorbtive question, it does neither, though the result is the same as doing both, within some spectral limits

what it does is increase the effective mass of the surface applied to and thereby require more energy to make it vibrate - its semi-pliant nature is extremely effective

so, while it does not absorb the sound wave itself, what it does is make the surface less capable of reflecting or vibrating sound energy

the result is the elimination of a lot of noise that would otherwise interfere with the ability of the speaker to generate full spectrum sound

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[Ryan]

Every object has a resonate frequency. The Dynamat lowers the frequency out of the audible range. Or at least a less sensitive range.

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[968kid]

All good stuff, thank you Gents. For some reason I was thinking the dynamat was creating a better surface for the reflexive waves emanating from the speaker, acting like a speaker cabinet. But evidently it cancels the sound coming in from the sheet metal, allowing for an un-obscured signal from the source.

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[Cloud9...68]

I know there's been some discussion as the the effectiveness of Dynamat vs. some other brands of sound deadening material, primarily B-Quiet. Has anybody ever heard of a brand called Cache? It retails for about the same as Dynamat Xtreme, but I found a guy locally who has an unopened box of ten 4 square foot sheets (the same 18" x 32" sheets Dynamat sells in their 36 sq ft box) that he's selling for $80. It's more material than I need to finish my job (I've put Dynamat in the doors, and now want to do the rear hatch area and the rear wheel wells - I know, I know, I should have bought the large box of Dynamat in the first place), but if this stuff is the equivalent of Dynamat, I might make him an offer. Does anybody have any information as to the effectiveness of Cache compared to Dynamat? Or is there a web site somewhere that might have some comparative test results for the different brands? Thanks.

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