[BlueWizard]

A nail or thumbtack, a string, and a pencil.

Tie the string with one end on the tack, the other on the pencil, and the length as needed.

Pin the tack at the wall/ceiling junction, and mark out from the wall, the proper distance.

Next pin the tack to the center speaker mark with the string at the distance needed between the speakers; mark to the left and right. Where this mark intersects with the previous distance from the wall mark, is now the exact center of you left and right speakers. Where the thumbtack hole is on the center speaker from the wall mark, is the center of that speaker.

Steve/bluewizard