CHAPTER 11 Equalisation 11.1 The Need for Equalisation 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. Moving along the audio chain still further, equalisation can also be used to modify the response of the room itself, by cancelling resonances with dips or notches in the overall amplitude response. However, it is not normally considered a good idea to try to combine an active crossover with a room equaliser, not least because they are doing quite different jobs. Moving the loudspeakers from one listening space to another will not require adjustment of the crossover, except insofar as the loudspeaker placement with regard to walls and corners has changed, but would almost certainly require a room equaliser to be re-adjusted unless the room dimensions, which determine its resonances, happen to be the same. At low audio frequencies, normal rooms (i.e., not anechoic chambers with enormous sound