The graphic equaliser is now commonplace on many HiFi systems. Its operation is very simple and is an extension of the traditional bass and treble controls found on even the earliest music systems. A graphic equaliser allows bands of audio frequency to be `cut' or `boosted' (ie. reduced or emphasised) to accommodate listeners preferences and to compensate for different room acoustics.
The number of frequency slots into which the overall sound is divided dictates the degree of control provided. These slots are called `bands' so we often see `5 band,' `7 band' and even `9 band' equalisers available. The central position is called a `flat response' which means the audio within that frequency band is played at its natural amplitude.
