Tom, isn't this a given? I mean, even without TacT, isn't there only one sweet spot. Move a little bit to the right or left, or raise or lower the listening chair, and, depending on the speakers and room, one may have vacated the sweet spot.
This is what I meant and I think we agree here. I don't doubt the efficacy of digital room correction. It can work very well indeed to compensate for lack of room or set up symmetry. But whether or not one uses a digital room correction device, the sweet spot stays small.