Do you adjust your subwoofer

Mine is a set it and forget it component.  The sub's output should be proportionate to the rest of the system, and controlled by the main volume. Occasionally I'll make a minor adjustment, but the sub settings have an unofficial default setting that I've deemed ideal for the room and system.

My secondary system shares space with our modest home theater.  Both have separate subs.  The crossover and volume are quite different in both systems. The home theater crossover is higher,as welll as the volume. That is for the extra boom for movies. 

Hell yeah. Second system. No sub on main. Depends on the mood. REL S3 SHOs. Different recordings have different levels so I might make a few tweaks now and then.

The science answer would refer you to Fletcher-Munson and Harman curves. The subjectivist says turn to where it sounds right for what you're listening to. The purist epoxies the level knob in place only after excruciating critical listening sessions with curated selections. At the end of the day, you'll set it where you like the best, and don't have to mess with it too often 

I have two SVS Ultra 13subs with upgraded plate amps and now I can control all the settings on the subs through the SVS DSP app on my smart phone My tower speakers have built-in powered subs also, I have my SVS subs crossed over at 40 hz and sub volume relatively low  Depending on what's playing on my streaming play list i will tweak the volume and crossover on the fly  It's so easy to return it back to the original settings