I have a 10" Sony Xplod, i know its not the best but its great for my needs. It is very loud in the car, outside the car you can't hear it at all. When i open up the hatch i can put my ear like a foot away from it because it sounds so quiet but when i close the hatch and get in the car, its banging! this always confused me, why is it like this? I can't seem to think that the sound resonance would amplify it this much

 

I had two 15s in a sealed box in my Tiburon that would bang hard with the hatch closed, but didn't hit worth a crap with it open. maybe just the way it bounces off the hatch?