Speaker Placement

Abstract, pls excuse my misunderstanding, but is this 40 inches from planer to back wall? Regarding rules of 3rds, I had active panels (Audioexklusiv 3A) placed 2/3 from side walls, 3/3 between them, 3/3 or 4/3 from panel to back wall (depending upon listening position, 4/3 for further away). This is panel centre-to-centre.
I got excellent soundstaging without toe-in (as you, I used female vocals).

I think from Redkiwi's post that front wall is the front wall that the listener faces and is behind the speakers. I am used to calling that the back wall as you point out in your post, but I wanted to be consistent with Redkiwi's original thread. So it's 40 inches to the wall behind the speakers.

Forgot to mention, I had mine 42 inches from the back/front wall.
To tackle one of Redkiwi's questions, "...shifting speakers closer to optimum position":
A)soundstage started expanding beyond the speakers to reach room boundaries
B)image stability and depth enter the scene, esp. the former. The piano, say, would not perceptibly shift position depending on the octave the pianist is stiking (typically, left hand or right...). Similarly with female voices. I wonder if you've encountered this.

I saw some refreshing new insights into speaker placement at
www.immediasound.com/Speakersetup.html
Departs from rigid Cardas type perfect symetrical setup, and encourages different toe-in each speaker and trying
moving one speaker closer/further from speaker wall to acheive balance. Given the fact that almost no one has exactly equal hearing ability in each ear, and various
wall treatments and furniture placements this is worth reading and trying some ideas.

My PSB Silver-I speakers are 5ft from speaker wall, 6ft apart, and I sit 7ft back from speakers....classic nearfield
arrangement. However I do use different toe-in each speaker, and one speaker is 4" closer to acheive my preferred balance. All depends on your room and individual hearing ability.

Intersting Sam: My speakers ended up with non symetrical placement that was arrived at through trial and ear. The left speaker is 21" from the front wall and 6' from the side wall. There are (almost) floor to ceiling standard bookshelves directly behind it but there is also an open doorway to the left and behind this speaker. The left speaker has no toe-in and I some times partially cover the open doorway with a hall closet door that opens up to the doorway and cock it at an angle. The doorway has a pocket door as well, but I do not care for the sound when it is used in any position, so just leave it in the wall. The right speaker is 25" from the back wall with the bookshelves also directly behind it but is 8' from the side wall instead of 6'. This speaker has a slight toe-in. The speakers measure 5 1/2' from tweeter to tweeter. The left speaker fires directly into the living room and the right speaker (with toe-in) fires into the living room but also partly to the dining and kitchen area (the kitchen starts approx. 12' back from the front wall and the whole setup is a horseshoe arrangement with a center wall running half the length of the room (starting from the back wall and extending to the middle of the room). The center wall divides the living room and the kitchen. If the kitchen were completely walled off (which it is not as it has an open end) the setup would be the typical and dreaded "L" shaped room. The sound is fairly nice throughout the living room (especially on the left wall, opposite the center wall and where the sofa is located), but when I get serious I position myself in a chair dead center and 7-8 feet back from the speakers. There is a bentwood/cane settee behind/between the speakers that doesn't seem to make a great deal of difference in the sound. I can't decide whether it's good or bad is one way to descibe its effect. Although the speakers are very close together the sound stage often exceeds the boundaries of the side walls (more so on the left side wall), especially since the addition of the 300B SET amp and a pair of Svetlana output tubes. Swapping the small signal tubes in the amp not only changes detail and tonality but also the height as well as the width of the sound stage and the "size" of the instruments within the sound stage (if this makes any sense). Sometimes Krall has a huge mouth and sometimes it's smaller, depending on the tubes used. Because of all the new variables that I have been dealing with lately, I havn't posted much about the "current" state of affairs with my system. I am still trying to figure it out. I have wanted to post photos of this setup as it is one of the strangest ones that I have ever had, but it really sounds OK all things considered (not great but OK). Other than bookshelves on two other walls of the room I can't imagine why though.