What Axiom subwoofer(s) do you own?

2 x EP500

Where do you have the Level, Frequency, Phase, and Subsonic Filter (if applicable) controls set?

9 o'clock on both, bypass, zero deg, N/A

How are you connecting your signal source to the subwoofer (RCA/XLR/High Level)?

RCA

What receiver/processor/pre-amp/integrated amplifier are you using?

Denon 4306 with all RCA outputs connected to A1400-8

What are you using for your main speakers?

M80 v2

Where do you have the crossover frequency and trim levels set in your processor/receiver for your main speakers and your Axiom subwoofer?

EP500's on bypass crossover with flat trim

Receiver:
LFE+Main mode
M80's - small 60Hz
VP150 - small 80Hz
QS8's - small 90Hz
LFE - 80Hz

Are you using the trigger on your subwoofer?

Yes, in cascading mode (i.e. Denon 4306 --> 1st EP500 --> 2nd EP500)