99' Discovery 2 with the Harmon upgrade sound system. The rear door has a bass module on the inside that vibrates horribly. I went through it making sure all the screws were tight and that both of the little 6"? rounds weren't blown. All seemed fine. Also annoying is vibration on the license plate assembly behind it. I know I'm not the only one because I've heard other Discoverys driving around with that damn rear liscene plate buzzing. Any quick fixes?

 

Go to the hardware store, buy a small sheet of adhesive backed rubber bumpers, remove your license plate, adhere the bumpers in a well distributed pattern to the back of the plate, reattach the license plate by screwing down well perhaps including rubber washers as well. Second method is to get the plate off the door completely by using longer license plate screws and nylon or rubber spacers between the plate and the door. As far as other vibrations are concerned, sometimes not easy to track down, but there is a shotgun approach in the form of damping kits available in auto audio specialty stores and probably via mail order from Crutchfield. Good luck

 

as far as the interior is concerned, invest in some dynamat... remove the enclosure and line the whole thing and the inside of the door with it

this will help a LOT and dampen further spread of vibration damage

 

B-Quiet Ultimate is much cheaper than Dynamat, I did my entire interior with that, L-Comp and studio foam where it would fit. The truck is still noisy bu most of the noise is road noise from the mud tires now.

One thing you can do to help is mass load the plate. Bolt the plate to something heavier then bolt that to the vehicle. Put a rubber sheet between to stop high frequency vibration. I.E. Cut an aluminum plate 'blank' to go behind it and bolt it to that securely, the more mass the lower the resonance frequency and the less vibration you'll see.

I'm surprised the stock subs are doing that though, they're really just a couple midrange speakers If you pull the door panel off you may find something inside causing vibration, loose handle mounting bracket for example.