Alan, what's worked fairly well in practice for me is what I first learned from the research of Roy Allison(June 1974 AES Journal, August 1976 Stereo Review, August 1994 Audio). The point appears to be that it isn't necessarily how close the speaker is to any one room boundary, but rather how the distances to the floor and each wall differ from each other. Allison showed that, for example,a bookshelf speaker with the woofer raised 2 feet from the floor on a stand but also 2 feet from each wall would show a greater coloration from the room boundary effects than that speaker on the floor, but 3 feet from the side wall and 5 feet from the front wall( or vice-versa).
