Crosstalk Cancellation for Spherical Loudspeaker Arrays

Spherical loudspeaker arrays for directivity pattern synthesis of natural sound sources have been recently reconsidered in electro-acoustic research [3, 4, 5]. Quite some time after the pioneering works in that field [1, 2], multichannel hardware and computational resources are easy to obtain, and the design and control issues receive increased interest. The loudspeaker arrays considered here consist of transducers mounted into the rigid surface of a spherical or polyhedral shell. The enclosure volume in this shell acoustically couples the motion of the transducer cones. Directivity pattern synthesis, however, requires individual control over these motions. On one hand, encapsulated enclosures behind each transducer minimize acoustic coupling. On the other hand, a shared enclosure is easy to construct and supports playback at low frequencies. To control the acoustically coupled loudspeakers in that case, a computationally expensive multiple-input-multiple-output cross-talk canceller (MIMO-XTC) has to be employed. This work discusses a spherical harmonics subspace approach for MIMO-XTC in rigid spherical/platonic loudspeaker arrays. It can be shown that matrices involved in the MIMO-XTC task become sparse within the spherical harmonics subspace, and largely reduce the computational demands.