Anotherspeaker placement question (distance measurements)

@immatthewj   Hope this helps.

Focal, who know something about speakers, uses a flexible equation to find the best speaker placement.

“Optimisation For perfectionists, here is a formula for optimal positioning: If A is the distance from the centre of the woofer to the nearest floor or wall, B is the distance to the next closest floor or wall, and C is the greatest distance (A < B < C), the equation B2 = AC defines the ideal loudspeaker position. • Example: If the centre of the woofer is 20” (50cm) away from the rear wall (A) and 24” (60cm) above the floor (B), then the side wall will be ideally 28” (72cm) away [C = B2 ⁄ A = 28” 

I found this a little confusing at first, but it became clear in short order.  There are three distances involved.  Floor to center of woofer, Side Wall to center of woofer and rear wall to canter of woofer.  The shortest distance is always “A”.  This is usually floor to center which is the only constant.  The next shortest distance is always “B”, and the longest distance is always “C”.  The distance “C” is always (B x B) divided by A. 

By example, if your floor to woofer is 24 inches, and you are 30 inches from the side wall, you would need to be 37.5 inches off the rear wall.  Find the numbers that work for your space and see how you like the sound.  

In a nutshell, Focal suggests there is no rule about distance from any wall as long as C = (B x B) / A

There are some great calculations and theories for optimum placement available to us, but none of them address the variables that are unique to your room, so they aren't an absolute or one size fits all solution.  Use those theories and calculations as a starting point, but don't be afraid to experiment and find what's optimal for your room.  If it pleases you and works in your room, it not wrong. 😉

I always use the center of the woofer.

That is; From side wall to center of the woofer and from the wall behind the speaker to the center of the woofer (at the front of the cabinet).

Same thing when measuring distance between speakers, from center to center of the woofers.

ozzy

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?