how are they hooked up...did you make sure that they are wired correctly,did u move the wires around to make sure it wanst the connection being shorted out or wires broken.....are they a 2.1 set or are they seperate speakers....
Speakers have got a magnet inside fabricated with special glue. After long time of use the glue becomes hard but brittle and at certain times mishandling or accidentally falling of speakers the hard glue gets destroyed and the magnet coz of repulsion looses its position and the sound is stopped.