Genelec Speaker Angle App ($.99) will help you create a symmetrical speaker setup that will deliver the fullest fidelity.
Theory: From my experience, most speakers benefit from angling or toeing-in toward the listening position. The amount of degrees for stereo speakers can depend on a variety of factors including room acoustics, and speaker design. Most of my fellow audio engineers agree that some degree of angling-in is preffered to a flat-facing forward speaker position. Achieving the best angle will take some testing with your own ears. For 5.1 surround sound the ITU (International Telecommunications Union) standard specifies a specific degree for front and rear speakers to be angled. The distance of each speaker from the listener is recommended to be equal, but odd room sizes can make this difficult. The Speaker Angle App will at least ensure that a symmetrical position is achieved from left to right, and rear surround speakers.
In Use: Using this App proved to be very easy indeed. Creating an equilateral listening position (sitting the same distance from stereo speakers as they are apart or wide) allowed me to test several angles before settling on what I felt best represented the stereo field. Placing the iPhone on top of my front right speaker (which I alligned flush at 0 degrees by facing my speaker forward) and tapping that speakers alignment tool allowed for each degree to be displayed as I angled (or toed-in) in the right speaker. I used this measurement to match my left stereo speaker to the right's angle. This took the guess work out of speaker matching and allowed me to more quickly arrive at an optimized speaker angle. If you want to extract the most from your stereo or surround sound system, then this handy app from Genelec is a worth a look. Take all the guess work out of matching speaker angles, and start enjoying the best sound delivery. (Images: iPhone screen shots & Vahan Baladouni)