The timing reference is just an option you enable while taking a sweep. Basically REW will use whatever regular speaker you choose as a timing reference to chirp before it sweeps the sub. It uses this to calculate the relative delay between each sub sweep and the stationary “timing” speaker.Question: when you say "run a REW sweep with timing reference," what exactly does that mean? It's the "timing reference" that I'm unfamiliar with (I haven't used REW yet, just watched a bunch of tutorials) - is that just a standard sweep or is there some extra step/box to check?
Also, when you say each of the possible locations: how accurate to you need to be here? Are we talking moving the sub 2 inches each time, or 6 inches each time, or a foot each time?
I just do sweeps of each general location to get an idea. While small moves of a foot or less have “some” impact, that is something I do after I locate the best general areas. A sweep that looks terrible isn’t going to look incredible if you move it 6 inches.