I have not tried to wire them in series yet. I have one wired to the front main left, one on front main right, one on back left, and one on back right. I was playing with all the settings again last night with the sub unhooked so I can just hear the speakers. I had to turn the back set of speakers off because now they are getting a loud humm in them. The sub is a cerwin vega 10" down firing. I can get the model number tonight. The sub used to hit a lot harder with the old receiver also. I notice the receiver has a setting that won't let anything below 60 hz go to any of the speakers. That is the lowest I can set the built in crossover. Settings are 60 hz, 80 hz, 100 hz, and 120 hz. I think this is what is creating my biggest problem with this receicer.