Your right sorry, my mistake the AVR is THX certified I had it confused with another model.
For speaker type "Normal" can this be changed to small?
Low frequency information below 120Hz is, for the most part, non-directional, meaning that even if the info is “crossing over” from a surround channel, you won’t know it. The effect will still sound like its coming from the surround, thanks to the principles of psycho-acoustics. If you are concerned with changing the crossover point for the subwoofer start at 100Hz then change to 120Hz and see if that helps.
Also, have you done a system reset as Scott suggested as it might help the AVR pick up the Sub when running Audyssey.