A subwoofer is generally built to be best suited for an enclosure of a certain size. The bigger the subwoofer, the greater volume it requires within the sub-box. So, to make the subwoofer sound optimally, its dimensions in the box must be in line with the subwoofer's size. If you want a 10-inch subwoofer, the ideal dimensions are at the very least 11 inches wide and 11 inches tall with a depth of 11 inches.