Randy, the rule of thumb to calibrate the sub flat with the speakers at 75db using the RS SPL metre is to set the sub at 72.5db so you may want to bump up your sub gain by 1.5 db using 40hz as the reference. Also you may get flatter response at a location closer to the seats on your left sidewall. In any event I would try to place the sub to minimize that peak at 80hz. The EP600H works just as well standing up and the small posts would be facing the front. Your direct graph shows why running the system to duplicate bass through speakers and sub is usually not a good idea.

That huge null at 120hz is a problem. Perhaps moving the speakers a bit further apart or moving the seats slightly will help. Also I would experiment with a 100hz crossover and see if that helps reduce breadth of the null. Blending the speakers with the sub to obtain flat response at the crossover point is very important to getting good system integration.

Here is one of my recent graphs. I had reasonable response but had to tame several peaks with an SMS equalizer to get it this flat.



John