Inside skin or inside panel is there a difference ?

Hello all, to those that have used sound dedining material on your doors. Is there a difference or preference to improve the audio experience in your car of using sound deadening material on the inside of the outer skin/panel of the door or is it better to cover the inner panel of the door ? I don't have a lot of $$ so I can only do one or the other. Thank you for your help.

 

I didn’t do the whole door , just a big square section around the speaker . And used fast rings to help focus the sound more to the inside instead of it sounding spread out.

 

sound deadening is a vibrational damper. meaning that it changes the frequency that things resonate and move at by adding mass. because the goal is only to reduce the 'floppiness' of the panels, it's minimally useful to cover every single panel fully-- it does provide an advantage, but not as significant as altering the 'floppiness' of the large flat panels, of which would require signficantly less damping material.

see this post:
https://www.ft86club.com/forums/showpost.php?p=3435403&postcount=2