I have been told it is good to form an equilateral triangle with you and the speakers.

example: if you measure straight from your ear to one of the speakers(not from your ear to the tv) and it is 10 feet, then you should have 10 feet between the two main speakers as well. (or each one should be 5 feet from the center of the TV).


If you are talking about the picture shown in this article:
http://www.axiomaudio.com/home_theater_layout.html

the 30 degree angle would create the equilateral triangle mentioned above.



-David