Editing Audio crossover (section)

====Notched====
There is a class of crossover filters that produce null responses in the high-pass and low-pass outputs at frequencies close to the crossover frequency. Within their respective stopbands, the outputs have a high initial rate of attenuation, while the sum of their outputs has a flat all-pass response. Their two outputs maintain a constant zero-phase difference across the transition, thus enhancing their lobing performance with noncoincident loudspeaker drivers.<ref name="Thiele2000" />