Rattle in jeep from system

I just installed a new stereo system in my jeep. I don't know the wattage or any of that but it is very loud and now my trunk is rattling! It seems to be coming from under the car rather than in the lift gate. Has anyone had this problem and how can I try to get rid of it myself rather than paying up the ying to have it fixed by someone else? HELP!:rolleyes:

I have 2 10 inch subs in my 97 Grand. All I had to do was Dynomat the lisence plate.

KJC

Cheaper than dynomat. Buy a section of carpet padding, trim it about a 1/2 incher smaller than your plate, and reinstall.