Manual

11
2.3.6.1 ‘Least Possible’ Approach
The first and most obvious, which we will call the ‘least possible’ approach, is to leave the
majority of the programme uncompressed, forcing the compression to deal only with the
louder passages. This method has a definite psychological advantage in that one gets the
feeling that the majority of the programme remains unaffected. There is also some possible
technical merit (especially for legacy designs) in that the compressor is working ‘less often’
and over a restricted range, thereby avoiding some of the potential errors in the application.
The above graph illustrates this kind of approach. The situation here is that the programme
goes ‘over’ on the loud passages, so we seek to control the loud portion only by setting the
threshold relatively high (-5dBr) and setting the ratio high enough (ie. between 3:1 and 4:1)
to prevent the ‘over’. With the Oxford compressor, the threshold and gain make-up controls
can be used to accommodate this approach over a 24dB range of relative input levels, without
change in the sonic character of the programme.
This method has the major disadvantage of risking increased rate of change disturbance
because the transition between non-compressed and compressed programme regions is sharp.
There is therefore a considerable reliance on longer time constant settings in order to reduce
the sonic effects of the compression. In other words, we need to seek to control the rate of
change using time slewing rather than level progression. Whilst this approach would naturally
form a good basis for using the compressor as an audio effect, it is less suitable for composite
programme control.