Anotherspeaker placement question (distance measurements)

The key is you use something consistently, that is all. I always use the front plane and tweeter for toe in.   As you know, all the recommendations are only starting places. So, it only maters you use something consistently. 
 

As an example, the recommended starting toe in for my speakers is to cross the beams 18” behind my head in the listening position. In my room, they sound best…. by a large margin with zero toe in. None. 
 

So, it is really true. Formula are simply a starting point. For me, I did my movements over a year. I plunked them in the prescribed place. And listened for a couple months (they are really awesome speakers). I realized they were capable of disappearing, but were not and the soundstage was restricted. So, I toed them out some. Listened for a couple weeks. No question… better. Moved again. Better. Some folks move, listen, move, listen… in a day. I find that confusing. I prefer listening to the music and wholisticly appraising the change. 

Thanks to all for responding.

@bigtwin  , I did read your response in the other "room size" thread.  Like the OP of that one, I am working with a small space.  When you posted this formula, I did not, at that time, work with any of your measurements.  I just went back to take a look to see how it would apply to me, and the center of my midrange driver (these are monitors on stands) is 33"  You stated that floor to center is usually the shortest (therefore 'A') but it doesn't have to be, correct? 

@immatthewj  Correct.  The shorest distance can be any of the three.  I think normally there is a Bass driver on the bottom and therefore that would most often be the shortest of the three.  Use the formula and the speakers can be in a variety of positions.  In the end, it's how they sound to you.  Cheers.

  @bigtwin  , (I will make a correction & report that my woofer is about 33.75 & the formula with the variations I was calculating with was giving me numbers very close to that) math was never a strong subject for me (I think that is why I have such troubles with electrical theory) but I sat down with a pen, paper & a calculater (I am still living in the 20th century) & went to work with my constant which, using the formula you provided, had to become C.  (I did say that this room hsa small amount of clean space to work with)  I started experimenting with BxB which is the dimension I feel I have the least flexibility with (side-wall-to-speaker x side-wall-to-speaker) and found a B that would work in my space and then I started adding inches and 1/2 inches to B and calculated 6 speaker placements that will fit in my allotted space. 

I am going to start with the numbers for the formula that will put the speakers 27" from the rear wall & go from there being fully cognizant that this formula is not etched in stone & if I cannot make it work, all I am out is my time & if I do discover the lost chord . . . hey, far out, man!

BUT:

the formula does not make any recommendations for listener's distance (I suppose ear to tweeter is what I should be measuring?) and I have been living with the preconceived notion of an equilateral triangle.  Is that where you would put your chair (to start) if you were using this formula to place speakers?

@immatthewj  I start with the triangle rule and kerp in mind it's not the law.  Many suggest trying to keep the distance between speakers not less than 75% of the distance to your chair. Once I have my chair set, I will stand behind the speaker and aim them to focus just behind my head.  Once again, it's what works for you.  All these rules are only guidance to help each room and system give max enjoyment.  Have fun with it.