A signal processor for determining a plurality of drive signals for driving a plurality of loudspeakers (230; 410; 510) to cancel a reverberation effect in a listening area (430, 432, 435), wherein the signal processor is configured to: - drive the plurality of loudspeakers with an initial plurality of drive signals, - measure one or more audio signals at one or more measurement locations, determine (330; 604) from the one or more measured audio signals a plurality of measured physical coefficients in a basis of physical sound functions, such that a sum of the physical sound functions, weighted with the plurality of measured physical coefficients approximates the one or more measured audio signals, wherein at least half of the plurality of measured physical coefficients are zero, - determine (340; 604) a residual error between the plurality of measured physical coefficients and a plurality of desired physical coefficients, the plurality of desired physical coefficients are coefficient sets representing a desired multi zone sound field, - estimate (350; 606) a transfer function describing a transformation from the plurality of desired physical coefficients to the plurality of measured physical coefficients, based on the determined residual error, and - update (360; 608) the initial plurality of drive signals based on the estimated transfer function, wherein the signal processor is configured to repeatedly carry out the above steps; wherein the basis of physical sound functions is orthogonal with regard to an inner product that for a first vector b i and a second vector b j is representable as: 〈 b i | b j 〉 = ∫ R b i x b j x w x d x = σ ij wherein R is a reproduction region of the plurality of loudspeakers (230; 410; 510), the first vector b i and the second vector b j are vectors of measured physical coefficients corresponding to locations in the listening area, and w ( x) is a weighting function and σ ij is 1 for i=j and 0 otherwise; and wherein the transfer function assigns a zero-coupling between a first and a second coefficient of the basis of physical sound functions, wherein the transfer function is representable as a diagonal matrix U(k). - drive the plurality of loudspeakers with an initial plurality of drive signals, - measure one or more audio signals at one or more measurement locations, determine (330; 604) from the one or more measured audio signals a plurality of measured physical coefficients in a basis of physical sound functions, such that a sum of the physical sound functions, weighted with the plurality of measured physical coefficients approximates the one or more measured audio signals, wherein at least half of the plurality of measured physical coefficients are zero, - determine (340; 604) a residual error between the plurality of measured physical coefficients and a plurality of desired physical coefficients, the plurality of desired physical coefficients are coefficient sets representing a desired multi zone sound field, - estimate (350; 606) a transfer function describing a transformation from the plurality of desired physical coefficients to the plurality of measured physical coefficients, based on the determined residual error, and - update (360; 608) the initial plurality of drive signals based on the estimated transfer function, wherein R is a reproduction region of the plurality of loudspeakers (230; 410; 510), the first vector b i and the second vector b j are vectors of measured physical coefficients corresponding to locations in the listening area, and w ( x) is a weighting function and σ ij is 1 for i=j and 0 otherwise; and wherein the transfer function assigns a zero-coupling between a first and a second coefficient of the basis of physical sound functions, wherein the transfer function is representable as a diagonal matrix U(k).