Patent ID: 9191766
Filing Date: 2015-11-17
Classification: H04R,H04S

Abstract:
1. An all-pass filter design method for improving audio reproduction within a bass frequency range in a listening room comprising at least one loudspeaker and at least one listening position, the method comprises: providing, for the at least one loudspeaker, a group delay response to be equalized and associated with one pre-defined position in the listening room; and calculating filter coefficients for all-pass filters each arranged upstream to a one corresponding one of the at least one loudspeaker, the all-pass filters having a transfer characteristic such that the corresponding group delay response matches a predefined target group delay response, where the step of calculating filter coefficients comprises providing a frequency dependent group delay constraint defining a finite range which confines the group delay response of the all-pass filter; iteratively calculating updated filter coefficients such that an error norm assumes a minimum while complying with the group delay constraint, the error norm representing the deviation of the group delay response of the respective all pass filter from the corresponding target group delay response.