So, in my 36' deep room, taking the 1/3 concept, we'd be looking at Duettas 12' from front wall, 12' to listening position, and 12' listening position to rear wall?
Marc, if you are to follow Limage’s (moniker of the Magneplanar guru in Hong Kong) concept, and your room is a true rectangle (i.e. not truncated, no slanted walls) then, instead of 1/3, the ideal speaker location is more likely to be 40/60, 40% from front wall (wall at the back of speaker) to speaker, and 60% from speaker to back wall.
Again, if your room is a true rectangle, I would be very concern about these ratios, as 18 and 36 are multiples of 9, and 36 is also a multiple of 18. You may have serious problem with standing waves. You probably would want to get as further away from any multiples as possible, and aim for 1.3, 1.8, 2.3 etc. The 1.5, 2.5 etc. doesn’t seem to cause much problem, but I would try to avoid that also if possible. This is also an audio room design concept of Limage.
I have experienced Limage’s speaker placement and room dimension concepts in multiple rooms, and it has always worked great!
But then, since your room has slanted walls, all bets maybe off!
Not sure whether the following is the write-up that Ked has mentioned, but I suggest you take a look and experience moving your speakers accordingly to see whether this method works for your situation. With this Room Coupling concept, we are trying to find the “focal point” of the room, and it seems the sweet spot would remain pretty much the same no matter what speaker is used. So, your current Zu is already a good reference. In Limage’s old audio room, we compared the positioning of the small BBC LS3/5A and the Maggie 3.6, and the ideal location was pretty much exactly the same!
http://www.1pekingroad.com/zaspx/replies.aspx?topicsno=3&subjectno=874&uppersubjectno=874&sortby=updatedate&orderby=asc