Subwoofer placement

I agree with with Tom as that is where YOU sit.
If you move from that spot(even a foot)you will hear a big change in the bass.
Two subs even out the layer of bass,so if you move,it sounds more consistent.I'd never go back to one sub.
try putting her where you sit as Tom suggests(as that's your
sweet spot),happy subbing.

with single sub have it in your listening chair then crawl around on hands and knees to find best spot while playing rolling bass line.

corners or walls work well.

Also, if you crossover at fairly high level (60Hz or higher) then try to keep sub within 3 feet of mains to reduce group delay. Or else, use digital correction to delay mains and keep group time with sub.

Once you have placement, play accoustically recorded cello to integrate with volume and phase. Don't integrate using same bass line you used to place, you need to get upper bass working with bass.

Thanks all. Went through the "put the sub in the listening spot" trick, and it's a corner placement that's best. That's where it is now, and it's quite a big difference from the former center placement.