Well, theres got to be a way to amplifiy sound.. think about how a magnifying glass makes something look bigger, well light is a wave just like sound is (albeit sound is a compression wave rather than electromagnetic).. There's gotta be some sort of audio equivalent of a lens or maginfying glass.. something to take existing SPL force and make it louder... I know horns just collect all the waves and direct them in one direction, effectively concentrating the source of the sound in a certain direction, but given bass wavelengths are so **** long, horns are impractical for subs...
But think about a drum.. that was kinda my influence here.. small tump from a hammer or stick gives you a much louder sound.. maybe the pelxi window just needs to be fixed on strongly, and ported..