OK so here goes... I pulled the plug to the poweramp, leaving just the sub. This time I triple-checked the scales
Also, I did a waterfall - note that the scale is 600ms
The sub needs to be in precisely that corner, as can be seen from the room picture. I've placed it close to both walls - is that something I should experiment further with?
Seems like equalization would come in handy, surprise eh? Is the 1124 most suited for this or is there another option?
Are there any other obvious things I should do or check or refurniture?