ABSTRACT
There is not a great deal of information out there about the design of linear-phase filters, and some of what there is appears to be contradictory. The crossover here uses linear-phase filters as defined by Linear-X Systems Filtershop [6], which for a fourth-order linear-phase filter consists of two cascaded second-order stages; the first has a cutoff frequency of 1.334 and a Q of 1.316, while the second has a cutoff frequency of 0.7496 and a Q of 0.607. With this filter structure the crossover point is at −4.5 dB. The summed response with the outputs in-phase has a gentle +1.2 dB hump at crossover, dipping very slightly below the 0 dB line on either side; see Figure 4.53.
