Ive done my var after retrofit the dyna audio but i only did the doors allot of work and tbh the sound is better the bass i mean but the efford and the money if i knew back then what i know now i would not have done it saved me like 200 euro
Depends on how you do it. For speakers, your mounting location and enclosure make more of a difference than deadening. If you go factory, you lose those potential gains.
Few speakers are genuinely meant to be mounted in an infinite baffle scenario. They like an enclosure, and they like it
enclosed.
What you want to do with a door is seal it air tight away from the cabin space. That means all those little cutouts and things used to install window regulators and lighten things up need to be completely sealed with the deadening material. You want the back-wave of the driver to stay in the door or outside of the car. That's where your increased bass comes from in a factory location. The other option is to mount an enclosure to the door panel; which doesn't work easily on modern hard foam panels.
That's for audio, though. It's different than trying to quiet a car.
It's certainly an
option for keeping traffic noise out, and it does work very well, but most of the "noise" you notice in a car is being transmitted through body and shock mounts, as well as firewall, vibrating floor, roof, and wheel wells. The doors are actually quite stiff, in that regard. The wheel wells are stiff too, but they're right next to the tires and suspension; so all manner of frequencies get in there. Deadening and insulating those is about shutting them up as much as possible.
More expensive cars will typically feature many laminations of steel or aluminum in those areas to mitigate the issue, and then add deadening asphalt to appropriate areas (same as Dynamat, just a different material), and then carpet with a thick neoprene pad.