Originally Posted by 4DHD
If I am reading this right, you have two XOs in the sub line. The AVR is providing the 80 Hz XO. If your sub has a crossover/LFE switch then set it to LFE. Or if there are two inputs, one labeled crossover and the other LFE, then connect the AVR sub out to the LFE input. If there is only one coax input, then turn the sub's XO all the way up to its highest frequency.
Thanks for helping and sorry if what I'm about to say doesn't make sense, I'm still learning all this.
My sub has two inputs: Speaker level inputs (for when the receiver has no Sub Out) and Sub in (single RCA connector). My sub is connected via the latter to the Subwoofer pre-out output on my receiver.
The sub, however, does have 2 switches that interact with the crossover setting. One is Digital receiver and the other is ProLogic receiver. When set to digital, the crossover knob on the sub becomes inactive and does nothing to the signal. When set to Prologic receiver the knob becomes active.
So, I think this is the important part. The AVR-3600 does not appear to have the ability of setting the crossover for the subwoofer, you can only set the crossover for the speakers, so what I did is set all my speaker's crossover to 80Hz, switching my Subwoofer source type to Prologic (so the crossover knob on the sub becomes active) and set the crossover knob to 80Hz.
I hope this makes things clearer. I'm still a beginner.