Why is a single powered subwoofer getting involved with the mono amplifiers?
I have a single powered sub and simply Connect the rca cable to the back of it. My sub has volume and crossover settings on the back. It's a b&w asw 2000.
Newer subs require Wi-Fi access to adjust them which is troubling but it's the modern age I guess.
I use the sub output from the processor I have. My main speakers when I use my preamp for two channel listening don't use a subwoofer. Not really needed.