Shane Buettner wrote in the Audio Perfectionist Journal:
Warren
Hope this helps.I achieved the sound I liked best with the 2.4s just under 7 feet apart (center to center), with a distance of just over 9 feet from each speaker to the listening position (an included angle between the speakers and listener of considerably less than 60 degrees, which is less than Thiel’s user manual recommends).
In my 24.5' x 17.5' room the distance from the coaxial mid/tweeter to the respective side wall was just over 5 feet and each speaker was more than 5 feet from the front wall. This did not optimize bass performance in the room as there was little if any boundary reinforcement from this position, but produced the best soundstage with the most coherent, convincing, precise imaging and best soundstage depth.
Warren