I have just acquired a pair of Sharp stereo speakers that have an inbuilt sub-woofer. Each speaker has a separate set of connecting wires for the sub-woofer. Am I supposed to join the wires (positive to positive etc) and insert them into the same hole in the back of the stereo or should the sub-woofer wires be plugged into a separate hole. Do these speakers require a specific amplifier that has separate connections for normal speakers from the sub-woofers?