What determines speaker distance?


What determines the spacing between the speakers? I've seen a 1.3 formula for setting the distance between each. If I have a 9 foot distance from the speakers to the listening chair that would make the spacing approx 7 feet? Seems a little wide to get a good soundstage. Are there are any other "general" guidelines for getting a basic spacing between the two?
fishwater
The formula doesn't work well in my room b/c the speakers would then be in the middle of the room, not too wife friendly. The 7-9 feet seems a little more then where I am now. I think they are around 6'6" center to center, the soundstage improves as I keep adjusting but still not there. They (Vandy 2ce sigs) also sound too harsh with more than an inch of toe-in. I didn't think they would have any center image with 8-9' ft of spacing center to center. I'll continue moving them around & see where it gets me I just didn't know where most folks are running their speakers as a general rule of thumb.
Of course all this depends on your room etc., but a pretty good rule of thumb is an equilateral triangle. Maybe, you(the listener) just a tad furthur away from the speakers. If your speakers are 8 feet apart you should be at least 8 feet, perhaps, in some cases 9 feet from your speakers. Just one of those rules with a zillion exceptions. Listen and thee shall hear....warren
I couldn't help myself- the question had me rolling on the floor. But seriously, What I meant to say is put 'em where they sound the best to you....