Have found that my TV built in sub is pants so popped to my local shop for a cheap external sub. I picked up a Wharfedale moviestar 60+ and was told to connect the Left & Right phono from my DVD player. I pass the sound out from an optical connection as well as the tv only takes optical in for Dolby. As I'm using the sub-woofer as a standalone, do I connect L & R, or just one? And does the crossover setting make any difference if I haven't got any other speakers connected to the sub?