I appologize if this isn't the correct fourm. I just picked up my first surround sound system today and I have a few problems. 1)I can't get any sound out of the back speakers unless the reciever is set to "Movie Theater". If it's in "Straight" only the front speakers work. Is this normal? 2)When I use the THX Optimode sound test the back speakers don't have any sound. It comes from the front. What's the problem? 3)My reciever supports EX/ES soundtracks but I can never get any sound out of the back center except a slight buzz from the power going to it. I've tried several EX/ES films and nothing has happened. I've also followed the manual's instructions and checked the balance and its fine but I still don't get any sound. 4)Finally I've used a coaxial cable to connect my dvd player to my reciever using my reciever's coaxial input but I don't get any sound. I can only get sound if I use regular red and white cables. Could anyone offer some advice? I've triple checked my wiring so the problem must be with the way the reciever's set up. My reciever is a Yamaha HTR5750S Dolby Digital Receiver and the speakers are Yamaha NSP436B. Thanks.