man i heard about that lol... what i heard is: it has 2 be from 20-50Hz and it has 2 be like 148 dB or more
THATS WHAT I HEARD AT LEAST lol
its gotta be some serious power, like comp said somewhere around 150 dbs and the box has to be poorly made, cuze if its screwed in their good and tight it shouldnt happen. but then again if your hitting 148 db's you wouldnt be making crappy boxes for your subs
ill try it, jus play a tone cd wit a girl in the car and ask her what ones are best. ill let you know the results.