The Use of Graphic Equalisers
Equalisers may be used for corrective or creative purposes and the Klark Teknik DN360 is applicable in both live sound and studio applications.
For studio use, a pair of 1/3 octave equalisers might typically be used to compensate for deficiencies in the control room acoustics and in this instance, the precision allowed by 30 bands is a great advantage. Because it is almost impossible to set up an equaliser accurately without first analysing the room response, the centre frequencies of the filters have been chosen to correspond with those of the Klark Teknik spectrum analyser, the DN6000. In this way the readings can be transferred directly from the analyser to the equaliser.
It must be stressed however that even a good equaliser doesn't offer a complete solution where the room has severe, inherent acoustic problems. For example, standing waves and resonances cannot be made to disappear simply by using equalisation. True their effects can be reduced, but in a critical listening environment such as a studio control room or concert hall, efforts must be made to minimise these problems at source before equalisation is employed. Also, equalisation cannot overcome the lack of sound clarity caused by rooms with unduly long reverberation times though they may be able to effect some improvement in the intelligibility.
On the other hand, the sound company who may well have to set up in different venues night after night have little or no control over the acoustics of the buildings and so have to use equalisers to arrive at a compromise solution. Depending on the room, some compromises will be more successful than others. Again, effective use of the equaliser means employing the services of a spectrum analyser. It is however not always desirable to achieve a dead flat room response. For example, applying substantial amounts of bass boost to try and restore a weak bottom end is going to use up large amounts of amplifier power and the extra loudspeaker cone excursions so caused will rob the system of headroom and may cause distortion. The harmonics produced by an amplifier driven into clipping may also damage the high frequency drivers and will at any rate sound unpleasant
Therefore, reducing the low frequency output may produce real advantages by way of improved intelligibility and subjective naturalness and this is particularly true of buildings made from concrete or stone where much of the bass is reflected rather than absorbed. Equally, rolling off the high frequency end above 5kHz may also contribute to a more natural sound. The resulting house curve then is far from flat but may will be the ideal compromise. Depending on the individual sound system and the environment, the shape of the optimum house curve will vary and a degree of experience is needed in order to achieve the best results. It should also be borne in mind that the ideal house curves for pure speech and music will not be the same.
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Frequency Hz
Typical House Curve
13
