Skip to Main Content
We investigated the multipole loudspeaker array based on spherical harmonic expansion in the Cartesian coordinate system. The arrangement of the multipoles with the least number of loudspeaker units has been studied for 2nd order of spherical harmonic expansion. The directivity of the multipole array does not achieve ideal directivity of the spherical functions due to the asymmetrical arrangement. The multipole array was also applied to an end-fire array because a multipole array uses less loudspeakers than the spherical array if the look-direction is fixed. We compared the performance of the conventional least-squares design method and multipole array method for an end-fire array. The least squares method had a higher directivity due to the large number of variable coefficients. Nevertheless, the multipole array based on spherical harmonic expansion has advantages of easy setup in the Cartesian coordinate system, analytical directivity, and small number of filter coefficients.