Try to set the options correctly first.
If both systems are in the same room, and speakers connected to BM6500, set audio option to 2:
Press SOUND - 2 - STORE
Set video option to 0:
Press PICTURE - 0 - STORE
Standby LED should flash for confirmation.
If both systems are in diferent rooms set A.OPT to 2 and V.OPT to 2.
If you have a BEo4 consult the manual for option settings.
Now it should be possible to listen to TV sound via your BM6500 by selecting source (TV, DTV, V.AUX....).
Stefan