A bigger subwoofer gives more bass, but needs a bigger box. 10 and 12-inch woofers are most common. When buying a subwoofer always keep in mind that bigger size is not necessarily better. Types of boxes Free Air - subwoofers are either mounted under the rear deck or behind the rear seat of a car. This configuration will not work very well for hatchbacks.
Holes have to be cut where the woofers are to be mounted.
Since the woofers use the whole trunk as a box, the trunk has to be as sealed as possible from the cabin. Trunk can be isolated usually by putting particle board under the deck and behind the seat. Sealed - is the most common box and easiest to build. The box internal volume should be as close as possible to the recommended by the manufacturer. If a box is smaller than what it is supposed to be, the sound will be tighter, but more amplifier power will be required.