Looking for recommendations on how to set up a sub on a covered back porch\/patio. I have 2 RSL outdoor speakers mounted high and a polk psw10 sub. Patio is about 15 x 20' with walls on two adjacent sides. The amp is a Denon dra 800h with 2 sub pre outs. Initially, I have the sub close to the middle of the long wall and the crossover set to 100hz. Any thoughts about sub placement and the best crossover frequency?