70 Cuda 3-Speaker Dash - Only Center Speaker works

[indetrucks]

I have a factory 3 speaker dash in my Cuda. Until recently the 8-Track AM receiver did not work, but I sent it out to Barry's 8-track repair who fixed the 8-Track and also converted it to FM.  While out for repair, I also replaced the blown center speaker.  The car is very much stock and still retains the factory 3-Sspeaker crossover box and harness.  Everything appears plugged in, but only the center speaker works.  I fiddled with the balance controls etc, but still only center speaker sound.

Not sure where to start diagnosing the left/right inoperative dash speakers.  Any advice would be greatly appreciated, thanks! 

[pschlosser]

connect the center speaker to the left or right speaker wires, to test if the outer speakers see any audio signal.  If not, it's the crossover, if so, it's the speakers (which seems unlikely)

[indetrucks]

connect the center speaker to the left or right speaker wires, to test if the outer speakers see any audio signal.  If not, it's the crossover, if so, it's the speakers (which seems unlikely)

Thank you!  I didn't realize the crossover box controlled both the right and left speakers.  Do you think this might also be while I have to turn the radio volume to max just to hear it?