Either voice coil to the speaker is shorted, or the audio output section circuit to your receiver has shorted component/s at it. Disconnect all the speakers from the set, and check whether it shows any warning error like this. If dhows, the fault is within the receiver itself. If does not show any error message, switch off the set, and connect the speakers; one by one at a time, and try to find out which one is faulty. Be remember to switch OFF the power to the receiver, each time when one speaker box is connected. If you wish to get some details; check the site linked here. Pull up older posts. Surf the site with patience. http://electronicshelponline.blogspot.com/