On crosstalk cancellation and equalization with multiple loudspeakers for 3-D sound reproduction

People prefer to be able to enjoy spatial audio without wearing a headphone. Such a tethered device is anyway inconvenient and undesirable, if not cumbersome. Alternatively, 3-D sound can be delivered to a listener with loudspeakers. However, crosstalk arises, and the rendered binaural signals are distorted by room reverberation when arriving at the listener's two ears, which lead to the need for a crosstalk cancellation and equalization (CTCE) system. Classical CTCE systems employ only two loudspeakers, and their performance is usually unsatisfactory in practice. While the idea of using more loudspeakers has been investigated, it was never shown why using more loudspeakers is theoretically more advantageous for CTCE. In this letter, we will study this problem and demonstrate that with two loudspeakers, only a least-squares (LS) solution can be obtained, while using multiple loudspeakers, we have more options: either an LS solution or an exact solution for perfect CTCE. These findings are justified by simulations using real impulse responses measured in the varechoic chamber at Bell Labs.