I disagree. The OP's question implied that he was attempting to set up his speakers by measuring the placement. Newbee merely said to measure from the drivers.
Hmm, you and I understood the OP differently then. I would not make the same assumption as you have. I see that he's reading articles (plural) on speaker placement and some mention measurements. He seems to want to clarify those points the measurements were taken from. I would never have read into that he is subscribing to any one of those methods. Just that he was curious enough to read more than one article. That in itself would prompt me to offer suggestions, as you and others have. Furthermore, Newbee suggested what HE used as the points in question. He did not suggest subscribing to using a specific methodology.
Yes, I think we basically agree, though I'm not entirely sure. I agree with some of the things you said - as I've pointed out later, I do not think there is a single methodology to use, that, as a rule, will work with every room, including the Sumiko one you suggest. But then I only have half of your 50 years in this hobby. Do you get a gold watch or certificate for your wall when you reach that landmark? :-)
Yes, I did feel you came off as disagreeable and thank you for the apology. Call me thin-skinned, but the phrase "extremely naive concept" as well as the general tone of your post rubbed me the wrong way.
Newbee - Yes, you've described it better than I did; essentially a triangle where two sides are identical (distance from ear to driver, not ear to speaker plane), and the base is 83% of those sides. Again, a suggested starting point.
If you came at this with no suggested starting points at all you might very well put one speaker in a corner in front of you and the other to your left side facing away from you and see how the sound pressure suits the music. Keep moving them around until you figure it all out and the pressure is equalized, and measurements are strictly verboten.
Mockturtle - No worries. I have had systems in various small rooms and, again, ran into some of the same challenges you describe (per my response). Sometimes a good solution, I've found is an asymetric corner placement. Man, Roger Sanders did that with his panels at a couple of the shows I've been to and was able to achieve a pretty impressive soundstage considering the size of the panels vs the size of the room they were in. Very impressive.
Marco