The disclosure relates to an apparatus for generating a sound field on the basis of an input audio signal. The apparatus comprises a plurality of transducers, wherein each transducer is configured to be driven by a transducer driving signal ql of the respective transducer; a plurality of filters configured to generate for each transducer the transducer driving signal ql of the respective transducer; and a control unit configured to provide or receive a first transducer driving signal vector q0 of dimension L such that the gradient of J(q;ψ) with respect to q is zero in (q0;ψ0), the control unit is further configured to provide a second transducer driving signal vector {tilde over (q)} of dimension L such that the gradient of the cost function J(q;ψ) with respect to q is [approximately] zero in ({tilde over (q)}; {tilde over (ψ)}), the control unit is configured to provide the second transducer driving signal vector {tilde over (q)}.