Hey,
I'm researching what needs to be done to upgrade the sound system in my 2013 Porsche Panamera.
One issue at hand is that I won't be able to do much as far as mass-loading and sound-proofing to the inner door cavity due to the way they're designed, so any material I use will be limited to the front door trim panels and the face of the door itself.
Here's a screen grab from one of the videos I watched in my research showing what the door looks like:
The speaker upgrade will be either an 8" or a 6.5" mid-bass depending on the available depth (the stock size is 8").
My daily driver has 8"s in kick panels, so door rattles aren't an issue I've had to deal with in ages. My first instinct is to concentrate on the trim panel: mass loading and sound absorption/blocking material to fill the trim panel cavities, similar to this video from Batdog Garage.
For the door itself, I'm thinking just add a layer of MLV to cut resonance, and then a layer of an open cell/vinyl composite to cut some road noise infiltration (SecondSkin products or similar).
Any opinions, or hard lessons learned?