ABSTRACT
This chapter deals with bandpass and notch filters. Bandpass filters as such are rarely used in performing the basic band-splitting functions of a crossover, but they can be useful for equalisation purposes and are essential for putting together high-order allpass filters for time correction. Bandpass filters are essential for filler-driver crossover schemes. Notch filters can also be useful for equalisation, but their most important use is in the construction of notch crossovers, whether based on elliptical filters or other sorts of filtering. The Bainter filter is an extremely convenient building block for highpass filters, but not so much for lowpass filters, because a lowpass notch means gain on the low-frequency side of the notch, and this will often be highly inconvenient. Like Bainter filters, Boctor highpass or lowpass notch filters are frequently used as a component part of elliptical filters. A notch filter that can be tuned with one control can be useful in development work.
