One way or the other. Jumpers on BOTH speakers or no jumpers on BOTH speakers. You can always use short pieces of wire or even a paper clip for temporary jumpers. Just make sure you connect the (2) RED posts together and the (2) BLACK posts together.
Here's a picture and info:
http://www.cardas.com/content.php?area=oem&content_id=13&pagestring=Jumpers
Here's a picture and info:
http://www.cardas.com/content.php?area=oem&content_id=13&pagestring=Jumpers