I recently installed a 10" subwoofer, and two powerful 6x9s in the trunk of a dodge neon. Everything worked fine till we closed the trunk lid. We immediately received a loud low resonating feedbackish tone. When we opened the trunk the sound went away. It is apparently due to the 3 strong magnets proximity in a closed environment. How can I eliminate this issue? (other than moving them further away, the trunk is to small)