To reduce the ripple in a cascade g

To reduce the ripple in a cascade graphic equalizer’s magnitude response, Azizi [59] has proposed to use extra filter sections, which he calls ‘opposite’ filters, between the band filters in a cascade graphic equalizer. When the gain and Q value of the opposite filters are set appropriately, the ripple seen in the overall response can be reduced further. Lee et al. refined this method by allowing the Q value of theband filters to change with gain [64]. McGrath et al. developed an accurate graphic equalizing method by constructing each band filter using several cascaded second order filters so that its magnitude response approximates a cosine pulse, spanning one band only [65]. Such high order filters have reduced interference, while the overall computational cost of the graphic equalizer is increased. Chen et al. have proposed an optimization method, which needs good initial values and definition of the desired gain at command points as well as at additional intermediate frequency points and which then iteratively adjust the coefficients of the cascaded biquad filters to reduce the mean squared error [66].