I'm not familiar with the rear speakers, as I do not have any and have not worked with them...The door speakers are supposed to be subwoofers/woofers and are only supposed to emit low frequencies, tho I don't know the cutoff.....Either the stock amp or the head unit probably has the low pass frequency for the doors built in and at a set point(Probably the head unit). As far as the door speakers wiring, the left door I believe is the green wires, and the right door the purple wires. If you check your head unit plug you should be able to see these easily.....The wires with the brown going thru them is the negative in case you didn't know
Lou