Bipole

Technology / Home Audio / Bipole: A speaker design that uses two sets of drivers to generate equal amounts of sound both forward and backward, or side to side, with the two sounds being 'in phase.' In a home theater setup, bipole speakers are particularly effective at creating a full, diffuse soundfield when used as surround speakers placed behind the listening position. Some speakers offer both bipole and dipole modes.
Search Google for Bipole: