As a general principle for speaker positioning, the so-called equilateral triangle rule is used, where the listening distance is at least as big as the distance of the speakers from each other.
However, with dual channel stereo listening, it has been noted that it is better for the stereo image to have the listening distance bigger than the distance of the speakers from each other, e.g. 4:3 with the speaker directivity overlapping in front of the listening position.
This rule is also applicable to the front speakers (left-right) in home-theatre use. There should not be anything between the speaker and the listening location that would disrupt the spreading of the sound waves. It is highly recommended that the speakers are in direct line of sight from the listening position. Both speakers should be positioned in an acoustically similar location to achieve the best sound image. Hard surfaces, such as windows, strongly reflect mid-range/high range frequencies.
The distance from the side and the back wall should be at least 80 - 100 cm. The corner positioning with speaker close to both the back and side wall, is not recommended due to the overemphasis of the bass range. This emphasis can be muffled by placing the muffler in the reflex element. In order to achieve the best listening enjoyment in the listening room, it is worth trying several different positioning options.
The central loudspeaker of multi channel set-up should be placed closely to the live picture.