Goldpick
Chris Johnson
If out of warranty, and you have no joy tracking down the details, it may pay to check the connection from the speaker to the main board. The plug connection at the main board itself may be loose, or the solder joints at the speaker end may be loose or the wires may have completely parted ways with the speaker. Was it a sudden fault like your brothers, or did the speaker start to play up over time? Not sure if the above pic is exactly the same, but should be similar (only internal x-terra photo I could find on the net).
Just ensure you don't touch the electronics on the main board due to possible static build up.
Just ensure you don't touch the electronics on the main board due to possible static build up.