Klipsch Promedia speakers don't work with normal speaker wire. They have a 1/8" (3.5mm) mono socket in back. This cable is a cheap way to go from the standard 9 ft cable to 12 ft.

If you need more length, you either need a weird series of adapters or you will need to attach a mono plug to a speaker wire of your choice.

1/8" stereo extenders work also, but they are generally made for input signal levels and probably won't contain thick enough gauge wires.