In the Sonnox Oxford EQ, the highest and lowest bandpass sections can be independently
switched to shelving functions. Although shelving functions are
often considered elementary, they are by no means all the same
and their importance to the sound engineer should not be underestimated.
Various types in common use are considered to favour certain types
of use or are considered preferable by users of differing taste.
Our analysis of common shelving EQs has shown that one of the most
important differences in the sound of the shelving EQ is the response
around the band immediately below the HF section (and above the
LF section). Many of the most loved classical EQs have a degree
of 'overshoot' in this region (when in boost), either by design
or as a result of circuit limitations in legacy units. Therefore
most units can be characterised by control within this region of
the frequency response. In appreciation of the importance of this
parameter, the Sonnox Oxford EQ provides the facility to modify the response
in this region to provide differing styles of shelving EQ.
When the HF shelving function is selected, the Q control provides control of the 'overshoot' function.
With the Q control set to minimum (yellow plot) the section has no overshoot and performs a basic and accurate shelving function. This is most like the responses provided by the original SSL 4000 EQs and many other outboard units often described as 'clean' EQs. Although these are still very popular units, some engineers complain that they can sound harsh and overbearing in comparison with legacy EQs.
As the Q control is increased the overshoot factor is also increased. For instance the red plot shows the slight dip in the response at around 1.5KHz for a boosted HF setting of 6KHz. This has the effect of suppressing the perceived mid range boost that occurs with the previous 'clean' variety, reducing the apparent 'hardness' of the sound. This, along with the increased slope rate, provides more apparent definition to the EQ in the band of interest.
The purple plot shows the effect of the Q control in mid position. This produces a gain loss of around 10% (of the boost gain) in the overshoot region and further defines the effect described above. This setting provides a response most like the legacy Neve designs and their derivatives and the later SSL G series EQs. This response produces an optimum effect by providing what the ear expects to hear as the gain control is operated and can explain the enduring popularity and renowned musical qualities attributed to EQs of this type. At maximum (blue plot), the Q control provides for an overshoot of half the total boosted gain, i.e. for +20dB total HF boost the maximum loss in the overshoot region will be -10dB. The curves are symmetrical in cut and boost gain settings.
Shelving overshoot control
(HF shelf Q control) |
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| Click to enlarge |
When the HF shelving function is selected, the Q control provides control of the 'overshoot' function.
With the Q control set to minimum (yellow plot) the section has no overshoot and performs a basic and accurate shelving function. This is most like the responses provided by the original SSL 4000 EQs and many other outboard units often described as 'clean' EQs. Although these are still very popular units, some engineers complain that they can sound harsh and overbearing in comparison with legacy EQs.
As the Q control is increased the overshoot factor is also increased. For instance the red plot shows the slight dip in the response at around 1.5KHz for a boosted HF setting of 6KHz. This has the effect of suppressing the perceived mid range boost that occurs with the previous 'clean' variety, reducing the apparent 'hardness' of the sound. This, along with the increased slope rate, provides more apparent definition to the EQ in the band of interest.
The purple plot shows the effect of the Q control in mid position. This produces a gain loss of around 10% (of the boost gain) in the overshoot region and further defines the effect described above. This setting provides a response most like the legacy Neve designs and their derivatives and the later SSL G series EQs. This response produces an optimum effect by providing what the ear expects to hear as the gain control is operated and can explain the enduring popularity and renowned musical qualities attributed to EQs of this type. At maximum (blue plot), the Q control provides for an overshoot of half the total boosted gain, i.e. for +20dB total HF boost the maximum loss in the overshoot region will be -10dB. The curves are symmetrical in cut and boost gain settings.