Surround : Surround Panning and Mixing : Surround Panner Controls : Divergence Controls

Divergence Controls
Divergence determines the width of the panned signal with respect to neighboring speakers. (For more information, see the Pro Tools Sync & Surround Concepts Guide). There are three Divergence controls:
Front, Rear, and F/R Divergence
Provide separate, automatable divergence control over front speakers, rear speakers, and between front/rear, respectively.