Ok, just an idea I had to test for the correct sub distance. If you sent a frequency that both your fronts and sub could play sufficiently loud at the same time (say crossover frequency), couldn't you just adjust the sub distance until you get the maximum SPL output? Technically this would mean that your sub and mains are perfectly in phase (at the location you're testing at), which is the goal of the whole setup thing. Sure there may be some variation as you drop to lower frequencies due to different response times of the sub and mains, but crossover is the essential one to match, isn't it? I haven't tried this myself yet, but I may when finals are over. Has anyone tried this or know if it'll work (or why not)?
