speaker questions

i installed 4 tower speakers and a Boss MR1000 w/ pa. for some reason only channel 3 and 4 works loud and i can barely hear anything come out of the other two speakers. but when i use the mic, the speakers work fine and loud. anyone have this issue? i ran each speaker into each channel

Are the gains/sensitivity set the same? Should be a knob for channels 1/2 and another knob for channels 3/4.