So i recently completed a 5.1 set up using polk audio speakers. I have a sony DH520 receiver and I am trying to make sure i set up the 5.1 setup correctly. I have the correct pattern chosen and when i do tests online to make sure the speakers are correct the rear speakers produce the same noise at the same time. the front 3 all produce their own sound but when it comes to the left and right surround they tend to be in unison between the speakers. is this normal? Any suggestions would be great. Thanks!