ABSTRACT
It is often desirable to include an equaliser that can put a peak (like that of a resonant circuit) or a dip (essentially a broad notch) in the frequency response. This is particularly useful for correcting amplitude response irregularities in drive units. The circuit shown in Figure 11.11 is based on the Baxandall tone control concept, and is commonly used in lowend mixing consoles. It can implement a low-Q peak or dip of variable height, giving a flat response if the control is set centrally. The centre frequency can only be altered by changing the capacitor values. This equaliser is described as “adjustable” because it can be set to either peak or dip by any desired amount within its limits. It is unlikely you would want to incorporate a peak/dip control potentiometer in a production crossover, though it could be extremely useful during the development phase. In manufacture RV1 would be replaced by a pair of fixed resistors that give the desired response.
