SUBWOOFER horns are built underneath the floor in a cavity 1 meter deep. Each horn is driven by 8 x 18" (48 cm) woofers. A total of 16 woofers:eek: http://www.royaldevice.com/custom.htm#HORN%20SUBWOOFERS%20MADE%20IN%20BRICKS now this is out of the box thinking!