Generally, ProAc's sound best well out from both side walls and the back wall with significant toe-in, even to the point of slightly crossing them. For specific distances from the side walls and back wall, divide the room into 5th's, and 7th's and place them in some combination of odd dimensions from each wall. Otherwise do it by ear and put them in the spots that make them seem to disappear the best.
I'd set up the speakers on the long wall. Given the size of that speaker, I'd say you'd want a minimum of 15 feet for the long wall. More would be better. Then try to make sure that none of the dimensions are multiples of each other, i.e. don't make a room that's 16x24 with an 8 foot ceiling.
The good news is that ProAc's sound really bloody good even in the wrong spot in the wrong room, but optimizing things brings much better performance.
I'm running Response 5's in a room that's about 17x20 with 9 foot ceilings and it works very well.
A couple more tips:
Try to have no furniture between the speakers and try to use absorptive material on the wall behind the speakers centered around the height that your eyes look at when seated in your listening chair. Also treat the first reflection points on the side walls.
I'd set up the speakers on the long wall. Given the size of that speaker, I'd say you'd want a minimum of 15 feet for the long wall. More would be better. Then try to make sure that none of the dimensions are multiples of each other, i.e. don't make a room that's 16x24 with an 8 foot ceiling.
The good news is that ProAc's sound really bloody good even in the wrong spot in the wrong room, but optimizing things brings much better performance.
I'm running Response 5's in a room that's about 17x20 with 9 foot ceilings and it works very well.
A couple more tips:
Try to have no furniture between the speakers and try to use absorptive material on the wall behind the speakers centered around the height that your eyes look at when seated in your listening chair. Also treat the first reflection points on the side walls.