Very popular subwoofers these days include small, flat subwoofers that can be placed under the front seat. The height of flat active subwoofers varies from 6 to 8 cm. Once you measure the space under the seat and find the necessary approx. 8 cm, you have, as they say, won. Always aim when setting the seat to the lowest position, and also try sliding the seat so that there is no movement of any protruding part that could damage the flat subwoofer.