Hi Ned.

It all depends on the resistance of the
amp(2ohm or 4ohm stable) and the
subwoofer(4ohm or 2ohm dvc).

Go to this link http://www.crutchfieldadvisor.com/S-GQQawc1YgHU/learningcenter/car/subwoofers_dual.html
click wiring diagrams on the right of the page.

Hope this helps.

Louis.