Soundstage

Very cool speakers,
after years of trying the equilateral triangle at 8 feet 
and trying to extend the 8 feet feet listener to my rooms max of 8 ft 6 in
I tried something different .
My speakers manual suggested 8 feet apart and 8 to 10 feet from the listener , so what's the difference ?  
The angle from the listener to the speakers ,
from 60 degrees to 47.2 so if you haven't already maybe try
moving your speakers to 8 ft 10 in  apart with your 11 feet to the listener
you'll have an angle of 47.2 degrees .
Just a thought and maybe worth a try .
https://www.calculator.net/triangle-calculator.html?vc=&vx=132&vy=132&va=&vz=106&...

Don't know where this equilateral triangle deal came from but it is erroneous.  

Speaker setup is a two-step process. 

Step one, move them around relative to the walls listening for bass balance and tone. Listener position matters as much as speaker location so listen to each speaker location from closer and further away. Step One the speakers do not need to be perfectly equidistant or symmetrical, but pretty close. 

Step Two, now from the smoothest sounding location measure very accurately to get them perfectly equidistant and symmetrical. Listen for image focus and sound stage width and depth. Adjust the toe in very slightly and the image focus and depth will be greater. Adjust the toe out very slightly and the sound stage width will expand. Equidistance and symmetry must be precise each and every time or you will lose image focus and think it was due to changing toe when really it was sloppy symmetry. 

When you are happy with the balance you are done. Does not matter what the distances are. That is all simplified to the point of rubbish. This is how you do it. 

While reading this thread I began to wonder about the carpet on the wall behind the speakers. I put it there when the projection setup was installed, but there are other ways to darken the wall. Is that counter productive? The speakers are a pair of KEF Reference 1s supplement below 80 Hz by a pair of Velodyne HGS-15 with acoustic bass management. The equipment that used to be on an adjacent wall now resides in a low (20") rack between the KEFs. In the past I’ve avoided placing anything between the speakers, but the low rack between them makes for a neat setup. If I did move the rack, I’d leave the amp on the floor between the speakers so there would be only a pair of balanced cables running from the preamp to the amp.