A 12” subwoofer is a larger sized speaker. The placement of the subwoofer can be problematic, because many cars are not large enough to place it in the best spot for bass. This is frequently known as an under seat subwoofer, as it can be placed under a seat but is too large to go in the dash. Placing this subwoofer in a convertible can be tricky because it may be necessary to put it in the trunk. Many times trial and error is the best option to find the sweet spot for maximum bass.
Trunk: Placing the subwoofer in the trunk is not necessarily an issue, as it will cut through the back seat. It does need plenty of air in order to produce the maximum bass. Even with the subwoofer behind you, it’s still possible to get great bass all around you, even from the front. The main issue is getting the correct slop and crossover. The subwoofer may need to be propped up and surrounded by dampening material.
Distance: Ultimately the distance from the passengers will depend on the vehicle. It is best to experiment with the placement for the type of sound you want. Normally the further away the subwoofer is from the passengers, the louder the sound. Having the subwoofer very close to the passengers, such as under the seat, does not produce the best sound. This is all dependent on the space and material used in the interior.
Hatchback: A subwoofer in a hatchback vehicle can produce a great effect, because the sound is amplified as it bounces off the hatchback and moves into the passenger area.