The listening room comprises at least one loudspeaker and at least one listening position. The method comprises providing for each loudspeaker, a group delay response to be equalized associated with one pre-defined position within the listening room; calculating filter coefficients for all-pass filter(s) each arranged upstream to one corresponding loudspeaker, the all-pass filter(s) having a transfer characteristic such that the corresponding group delay response(s) match(es) a predefined target group delay response. The filter coefficients have a group delay response being confined by a frequency dependent group delay constraint that defines a frequency dependent interval exponentially decaying with increasing frequency.