You can't sketch it from my description?
Not with confidence (but I tried anyway, see the attached .pdf file).
Living room is 23 ft from south wall to center of the trigonal shaped north wall... The south is 11 ft long.
Assuming your architect's drawing is to scale, and the distance from the south wall to the center of the trigonal north wall is 23 feet, then it looks to me like the south wall (from the south-east corner westward to what I presume to be a kitchen cabinet) is a little over 14 feet, instead of 11 feet.
OR, again assuming your architect's drawing is to scale, if the south wall (from the south-east corner westward to what I presume to be a kitchen cabinet) is 11 feet, then it looks to me like the distance from the south wall to the center of the trigonal north wall is a little under 18 feet, instead of 23 feet.
... two 17" x 15" power amps need to go deep into that corner and a Don Sachs DS2 preamp about 1 ft in front of them. Then in front or along side of the preamp is the Merging Hapi DAC and a few feet further from the center of the corner, towards my chair a small desktop PC on the floor feeding the DAC via USB. And atop the pc a 17" monitor.
So these items go in front of the door that's in the south-east corner?
Is 7 to 9 ft center to center main speaker distance vs the corresponding listening distance considered a very wide listening area?
I got the impression that the listening area should be 8-10 feet WIDE (slightly wider than the center-to-center speaker spacing) from this:
As for listening sweet spot, am I right in assuming that if one has CD pattern waveguides with good horizontal coverage, then the off-axis response would be good enough where if the center of the speakers and I were placed ~ 9 ft equillaterally between each other then I could move 4 or 5 ft left or right without a drop in frequency response, yes?
Imo a listening area slightly wider than the center-to-center speaker spacing is an unusually wide listening area. Ime it can be done, but it calls for a horizontal radiation pattern about 90 degrees wide.
If you see where I have misunderstood you, please make corrections.
I would receive mostly constant output across the AF range and accross the 180 arc of both speakers within that ~ 5 ft wide sweet spot.
I don't know what that "180 arc" is referring to, and here it sounds like the sweet spot width you are seeking is only 5 feet wide, which imo would open up the possibility of using waveguides with horizontal patterns somewhat narrower than 90 degrees.
Again, please correct where I am misunderstanding you.
The speakers would be placed in that corner and the center to center distance between them would be somewhere between 7 and 9 ft, and I guess toed slightly out (?).
"Toed slightly out"? Maybe I'm misunderstanding you again... a time/intensity trading configuration calls for aggressive toe-
in.
Please advise if you think otherwise regarding placement.
How much freedom do you have as far as speaker placement in that room?
I'm not ignoring your other questions; I just want to get my confusion here cleared up first, because if I've misunderstood something important then I will need to re-think my suggestions.
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I have attached my best guess of the speaker locations assuming the 23-foot room dimension is correct, and have drawn them with the aggressive 45-degree-ballpark toe-in angle I have in mine. Let me know what I'm getting wrong.
Thanks!