For those of you who have added sound insulation (Dynamat, etc.), did it make a difference?

If it did, was it a big improvement, or just marginal?

 

Marginal.

The doors do make a nice "thunk" when you close them though

 

Small amounts of dynmat can solve for the tinny sound when panels vibrate. But you don't need to cover everything with it. eg. A 6 inch wide strip inside the door will do the technical job, a one foot square in the footwells, etc.

Some insulating rubber foam will also mute the reflected sounds, and I would use more of that than the dynamat.

I can only imagine the hassle of a future restorer dealing with butyl rubber fused to everything, degraded aluminum flaking off the dynamat, etc.

 

I haven't put it in my Ferrari (and won't). I let myself get talked into having it installed in my 911, and quite frankly it made no difference. Waste of money.

 

Not in my 328, haven't had the carpets out yet given the general condition of the car is not necessary .
I did it in my Lancia Montecarlo. Old ones cleaned up from the bottom and back wall and new ones installed, not the brand product but alternative. Keeps shaking with the buttocks

 

I see it used all the time but never understood what someone was trying to quiet.

For example, Dynamat on one with a Tubi...