i have cadillac cts with factory bose radio & amp, i have to keep both because one will not work without the other correctly. i have 6 partial channels, 2 for 100 hz & down, 2 for 100 hz -8khz, 2 for 8khz & up, all six of these make up only 2 full range channels, want to sum three together to make full range channel x 2, the speaker wires from the amp are hi level, after summing 3 to make full range channel have audio control lc2i, to change them from hi level to low level inputs to external amp, what size resistors will i need to sum 3 channels together to make 1 full range channel x 2 ? thanks
