Unlike a conventional speaker that creates audio waves by moving air as a result of the cone travelling in and out, this "exciter" speaker produces the audio waves by vibrating the flat panel it is fixed to.Install it on ceiling panels, under a table, on a wall partition, behind a fibreglass panel or other flat surface where a conventional speaker can't normally be used.They are low profile, and could be used in a sealed chamber in a marine application.Array them to increase sound level.