I used an equivalent product from JC Whitney (about $30 for a 32x54" sheet). They call it Sound/Vibration Dampening Sheets. You'll need 2 sheets for the the front and rear floor area. I used smaller pieces for flat areas of the door, tunnel and trunk areas to help dampen noise.
Dynamat is good too, but it's quite a bit more expensive. Since this is asphalt-based, excess weight is the result if used in large quantities. I saw a 525 audio-prepped Bimmer with the entire front cowling/bulkhead/wheel wells covered with Dynamat. Owner claimed about 300 lbs. added due to the Dynamat.
There might be newer, more effective and lighter materials for this purpose.
Sherwood Lee
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