I'll start by saying this: I'm an audio newbie. I recently purchased four Def Tech studio monitor 45s, a Def Tech 8040hd center, Def Tech prosub 800, and the Yamaha rx-v675. I plugged my iPhone into the usb port on the front of the receiver to listen to music, but I noticed my subwoofer wasn't hitting (front, center, and rear channels worked). I changed over to my PS3 and it works just fine. Do I have to change some sort of setting, or does the usb port not play music using the subwoofer?