See ive found a wall is concentrateing the soundwaves and air pressure in the front of the cab by the meter and listener along with shorteing the cabin space so easier to pressureize. Then with a box if you face it back the waves and pressure just have to bounce off the back of the hatch and they are concentrated straight to the front of the cabin, subs up port back the subs are boucing between the roof and floor, dont understand how it would become loud in anyway you know?