Are saying that people on here actually triple their efforts when they say they applied a layer of sound deadening? Or are you talking about a professional? Either the case, I have seen many installers put down exactly how many layers they say they would. Not sure why someone especially an installer would go the extra mile and give a customer 2 extra layer or even 4 extra layers (double deadend) for free. None the less, ventilation is good in our cars, allows you to shut your doors, keep condensation down, keeps mold down, etc.. But if you are try achieve a solid door or car for competition, SPL or SQ, you will want them completely sealed off. Its really a give and take situation.
Oh and if it takes a pro 5-6 hours per door, and they are only installing a few layers, they probably do not know what they are doing and they would most likely be fired. If they were even doing it leisurely, I still dont know what to think about that.
Back to the original poster, Like Hebrew said, I also Sandwhich my ensolite between my deadener. This is about the best approach I have come up with, without using acoustic foam. Foam is about the best bet for knocking down those unwanted noise. But you will only reach a certain reduction in different cars, until the windows and designs start to come into play. That of which you can usually do nothing about. Cars are just not the perfect enviroment for audio..I guess thats what pushes us to achieve better things in them?
I learned that from installers that work with expensive cars in expensive audio shops, not best-buy installers. //content.invisioncic.com/y282845/emoticons/confused.gif.e820e0216602db4765798ac39d28caa9.gif
In fact, it takes a shop 1-2 weeks to do proper audio install.