Can I add another sub?

[bhoup]

I currently have a Velodyne VRP-1000 sub hooked up to my Marantz SR7300 receiver but I am thinking about adding a second sub to help fill the room.

Currently I have the sub cable running from the pre-out of the receiver to an adapter like this: http://www.monoprice.com/products/pr...seq=1&format=2, which them plugs into the sub. How can I hook two subs up to my receiver? What adapters do I need if this can be done?

Thanks!