ABSTRACT
This chapter deals only with the equalisation of the frequency response, but there is another very important form of equalisation; this is commonly called time equalisation, time-delay compensation, or phase equalisation, and while its results can be seen in the form of an improved frequency response, the circuitry involved essentially works in the time domain, and in itself has a flat frequency response. Equalisation to attain a desired flat frequency response may be applied to correct problems in the loudspeaker itself or, moving along the audio chain, to modify the interaction of the loudspeaker with the room it is operating in. Drive unit equalisation usually involves the correction of minor humps and dips in the frequency response. The equalisation is typically performed by a highpass filter-boost equalizer. Dipole speakers are commonly regarded as needing equalisation in the form of a 6 dB/octave boost as frequency falls, starting from an appropriate frequency.
