For the front speakers, the normal rules apply. ÿYou're aiming for a triangle, with the listener at the apex. ÿIf the speakers are too close together, you won't get much of a soundstage. ÿToo far apart and you'll create a hole, with the sound lacking cohesion and seeming unconnected with your screen. ÿThere's plenty of advice/diagrams online. ÿThe need to cater for more than one listening position would be a further complication, of course.