^Thiel measured their speakers from a distance of 3 meters (approximately 10’), and a minimum of 8’ is required for driver integration and time alignment, aimed straight ahead. If I recall correctly, the 3 meter distance would have a convergence of 22 degrees behind the listener. As space allowed, close to an equilateral triangle for placement was recommended. So, in a room with available side wall space (at least 3’ and preferably 5’ or more) closer to 10’ apart center to center. As you have more than 5’ to side walls, closer to 10’ might work and provide for a bigger soundstage. The distance to listener is another variable to consider. If placed 10’ apart (center to center) and you have less than 10’ between listener and speaker, a bit of toe in might be needed. Toe in can be tricky, just a little bit goes a long way. Too much toe in, and you can shrink soundstage and perhaps even worse, introduce brightness. Another consideration would be the distance of woofer centers to front, rear and sidewalls, and though obviously less controllable, floor and ceiling. The ratios of which can be important for smoothing bass frequency. Simply put; it might be best not to have even multiples or divisibles of any of those distances.
FWIW, as I set up my Thiels, my room affords similar wide space between speakers and sidewalls, but regrettably doesn’t offer quite the ideal distance of listener to speaker. So, I set up mine 10’ apart (center to center), 7.5’ from center to sidewalls, cabinet backs 3’ from nearest wall, and a speaker to listener distance of 8.5’. with 2.5 degrees of toe in. If your room is similar to mine in that the back wall is close to the listener, I can’t emphasize how important some absorptive room treatment behind the listener can be!
Every room is different. Use the figures as a starting point and customize as necessary.
