In this paper, a method to extend the perceived spatial width of a virtual sound source using multiple loudspeakers is proposed. Control of perceived source width or apparent source width (ASW) has been attempted by decreasing the inter-aural correlation. For this purpose, numerous decorrelators were proposed for stereo loudspeakers or headphones. However, these techniques are inadequate for sound field reproduction system incorporating multiple loudspeakers. For sound field reproduction, extension of source width has to be realized with three requirements. First, extension should not deteriorate the localization cue, provided by the reproduction system. Second, the coloration artifact, which induces by extra wavefronts other than the direct wave, should be minimized. Most importantly, the effect of source width extension has to be maintained over a large listening area. To design a spatial decorrelator that can meet these requirements, we design a proper target sound field with reduced inter-aural correlation over a zone of interest. The target sound field is reproduced by loudspeakers driven from a multipole expansion technique. The performance of the proposed method is verified by examining the inter-aural correlation coefficient (IACC) of the reproduced sound field over a wide area, as well as the ITD and ILD distributions.