\rHi Greg,
You have two options for outdoor subwoofers; both are passive and will require power. The first is our OMSUB 200. You can drive this with your regular amp because it has a built-in crossover. See the diagram on the product page for wiring information. It basically goes in-line between the speakers. The second option is our RSUB300, which requires a sub amp like the SMP250. We sell it in a combo with both, and you would connect your Y adapter to the sub amp.
CL/MA 1969\r