Our TriAxial surround speakers have side drivers, where the one firing backwards in the room, is out of phase with the other drivers.
Therefore when mounting as the surround back channels in a seven-channel system, the in-phase drivers should be mounted pointing at each other in the center of the rear wall.
Meaning, the Left speaker should be placed in the Right position at the back wall, and the Right speaker on the Left side. You can tell the right/left apart, by looking for the R or L marking next to the serial number on the back.
This means the out-of-phase drivers are working in the correct phase with the out-of-phase drivers on the side channels.
Between them, this pairing continues to assist with placing pin-point images at the rear, whilst working with all of the other drivers to diffuse the sound field around these effects.