Vector Base Amplitude Panning (VBAP) is a method for positioning virtual sources to arbitrary directions using a setup of multiple loudspeakers. In VBAP the number of loudspeakers can be arbitrary, and they can be positioned in an arbitrary 2-D or 3-D setups. VBAP produces virtual sources that are as sharp as is possible with current loudspeaker configuration and amplitude panning methods, since it uses at one time the minimum number of loudspeakers needed, one, two, or three.
Check out the following links for further information:
V. Pulkki “Compensating displacement of amplitude-panned virtual sources.” Audio Engineering Society 22th Int. Conf. on Virtual, Synthetic and Entertainment Audio pp. 186-195. 2002 Espoo, Finland
V. Pulkki “Spatial Sound Generation and Perception by Amplitude Panning Techniques”