Comparison Between Time Delay Based and Non-Uniform Phase Based Equalization for Multi-Channel Loudspeaker-Room Responses
Traditionally, room response equalization is performed to improve sound quality at a listener. Given a loudspeaker and a listener, in a room, a loudspeaker-room response is obtained and an inverse filter is designed for loudspeaker-room magnitude response equalization. However, due to non-coincident positions of any two loudspeakers, in a multi-channel setup, the combined response of the two loudspeakers may have an undesired broad spectral notch or peak or large spectral deviations in the crossover region. These spectral deviations introduced around the crossover, due to the combined phase response, generally cannot be compensated with magnitude response equalization. In this paper, we compare two different methods (time delay and all-pass cascade) for correcting for the spectral deviations in the crossover region. We demonstrate that using non-uniform phase distribution, with all-pass filters, around the crossover region, as opposed to a constant phase (i.e., a fixed and optimized time delay in the satellite), it is possible to obtain better correction in the crossover region but with increased complexity. We also present an automatic approach for evaluating performance with the time-delay approach.
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