check out what clark has to say at...
http://www.clarksynthesis.com/whatis.php
they hook up to your reciever either via lfe or off your front mains.
placement is either in the floor, or in your seating. mine is in the stage that my seating is on. you can see it here
http://www.hometheaterforum.com/gall...g2_itemId=4443
where the 2 levels of my stage come together, there is a main support beam. on that beam, all other
joists are attached. in the center of that beam is the shaker. the idea being that anyone or anything on the stage will FEEL the bass - low/mids in their feet/butt/hands, not just hear it, or feel it in your chest like you do with typical subs.
Lots of fun, for not a lot of money, especially if you are building from scratch.
I've got an amp that i can remotely control crossover and volume. so if it is too much for my wifes (girl) movies, I can turn it down. then back up again when I watch explosions.