Hodu - I think 11x14 is more relevant to your situation than the 11x20.
I'm in a ~13 x 15 foot alcove myself. Facing the speakers that are positioned 7-8 ft apart along the long wall (not ideal)the right (13') side wall of the rectangle is missing. The alcove opens into a much larger space on that side (probably 3x the area). There's a pocket door in the left wall that I keep open while listening + left speaker placement is a good few feet from the wall and corner (also have some DIY room treatment in the corner).
I consider my listening area, which seems like it might be even more "open" than yours, to be 13x15...and don't worry about the larger space outside it. Tom6897's point is a good one. I sit 7-8 feet or so from the speakers that are out (front plane) ~3' from the wall. I like to listen at volumes in the range of 78-85 db. No problem doing so in this setting. Hope this helps a little.
I'm in a ~13 x 15 foot alcove myself. Facing the speakers that are positioned 7-8 ft apart along the long wall (not ideal)the right (13') side wall of the rectangle is missing. The alcove opens into a much larger space on that side (probably 3x the area). There's a pocket door in the left wall that I keep open while listening + left speaker placement is a good few feet from the wall and corner (also have some DIY room treatment in the corner).
I consider my listening area, which seems like it might be even more "open" than yours, to be 13x15...and don't worry about the larger space outside it. Tom6897's point is a good one. I sit 7-8 feet or so from the speakers that are out (front plane) ~3' from the wall. I like to listen at volumes in the range of 78-85 db. No problem doing so in this setting. Hope this helps a little.