The Oxford EQ and Filters plug-in draws on the considerable experience in professional audio and studio systems earned by the Oxford Team, the team that designed the OXF-R3 console system. The Oxford EQ plug-in is based on the OXF-R3 EQ section and provides a truly professional EQ processor for Pro Tools, VST and Audio Units users.
The Oxford EQ is a fully functional 5-band application with selectable shelf settings on LF and HF sections. Additionally, separate variable slope low pass and high pass filters are provided. The EQ also features four different selectable EQ types that cover most of the EQ styles currently popular amongst professional users, including some legacy styles, which are renowned for their artistic capability. The use of novel coefficient generation and intelligent processing design provides unparalleled performance that surpasses analogue EQ in both sound quality and artistic freedom.
An additional GML 8200 emulation is available for Pro Tools TDM and AAX DSP.
Programme equalisers have expanded beyond their original use as distance correction devices for film and vision, into highly creative tools that represent a leading part of the sound engineer’s artistic palette. A great many EQ designs have been developed over the years that have been attributed with qualities that lend themselves to particular uses and sounds. The Oxford EQ plug-in is designed to be flexible enough to address as many of these generic types as possible from a single application, by presenting a variety of types to the user. The following pages are presented as a general explanation of many of the factors that affect EQ performance, and to illustrate how we have addressed these issues with the Oxford EQ plug in.
Many types of EQ exist with many differences. One of the most important areas is the issue of control ranges and interaction. Whilst it is true that with a parametric unit with continuous controls (ie. not quantised) any response could be obtained by matching their curves, many of the popular EQs have control dependencies that err towards specific application. One of the main areas where EQs differ is Gain / Q dependency. Most analogue EQs have Gain / Q dependency as a result of the circuits used. This factor can greatly affect the artistic style that an EQ presents by facilitating certain parameter settings and encouraging particular uses when the unit is operated.
In the Oxford EQ plug-in we have covered this situation by providing three different styles of EQ that take account of Gain / Q dependency as well as overall control ranges.
The EQ and Filter controls are presented in a user-friendly layout, and the function of most of the knobs and switches should be immediately obvious. Full information on each control is provided in a later section of this manual: .
Note the numeric displays for each rotary control. These provide instant feedback of your EQ and Filter settings, in addition to the graphic ‘response display’ provided at the top of the plug-in layout. The numeric displays can either be activated when an EQ or Filter section is hovered over, or may be left on permanently (as shown in the example above). The choice is made in an option menu available via the Sonnox button (in the top left of the plug-in); more on this later.
Four options (also in the Sonnox menu) determine how the rotary controls (knobs) behave under mouse control.
The upper area of the Oxford EQ plug-in is taken up by the EQ and Filter response display:
In addition to more conventional knob control, the EQ can be controlled from this graph if the ‘drag handles’ option is selected via a drop-down options menu that appears when you click the Sonnox button in the top left of the display.
By default, the drag handles will be shown on the graph. Each drag handle corresponds to the EQ band or filter section knob caps that match the colour of the drag handle. For example, the dark blue drag handle controls the LF section, the red the MF section, the dark grey the low filter, etc. If not currently active, a band is automatically enabled when you drag its corresponding drag handle.
By default the vertical scale of the graph automatically adjusts itself to contain the yellow response line or all active handles – whichever is larger. The default graph scale, and other options, can be changed by clicking the Sonnox button and selecting the Graphs entry on the drop-down menu.
Note that the response graph setup is saved and restored across instances.
The graph display is designed to be as intuitive as possible.
Whenever a handle is being used, the numeric readout displays of the corresponding section will provide immediate feedback of which section is being used, and the precise values of your adjustments.
When a section is switched out, the handle remains true to the gain position of the control. Also note that moving a handle will automatically enable that section.
Bands IN
Bands OUT
There are two options in the menu accessed via the Sonnox button that allow you to configure the graph display for your preferred way of working:
You can disable the graph handles for a cleaner look if you prefer to use the more traditional knob and button controls, and don’t want to be tempted to use the handles:
This determins whether the coloured fill is displayed under each section:
This style has minimal Gain / Q dependency, smaller amounts of boost or cut still have relatively high Q, and it is therefore precise and well defined in use.
However it is sometimes difficult to obtain overall EQ fill on combined sources and subtle EQ on vocals and the like, as the user needs to adjust the Q control to maintain an effect when the gain is changed. Failure to understand this fact has often added to the reputation of this type of EQ for sounding ‘hard’ or ‘harsh’. However, because the user retains separate control of all its parameters, this EQ is still the most flexible for users that have the time and patience to spend when using it.
It is most like the original SSL 4000 Series, and other ‘clinical’ styles of EQ that became popular in the 1980’s.
Type 2 EQ is the same as Type 1 in boost, but has constant-Q responses in cut. This is the only type offered in the Oxford EQ that has unsymmetrical curves. Therefore EQ applied in a boost cannot be readily reversed by cutting afterwards. The EQ resembles some speciality legacy units, and lends itself well to resonance control for percussion instruments such as drums, since relatively high Q is available at low gain settings, whilst fairly subtle ‘fill EQ’ can be achieved using boost settings at the same time.
This style of EQ has a moderate amount of Gain / Q dependency whereby the Q reduces with gain. This provides the EQ with a softer characteristic as EQ is progressively applied and since the effective bandwidth is increased for low gain settings, it sounds louder and more impressive when used at moderate settings. The gentler Q curve also lends itself better to overall EQ fills and more subtle corrections in instrument and vocal sources. Turning the Gain control seems to produce the effect that the ear is expecting, without needing to adjust the Q control too often. Therefore EQs of this type are often dubbed as ‘more musical sounding’.
This EQ most resembles the older and well-loved Neve types, their modern derivatives and the later SSL G Series. Also many of the more popular outboard EQs have this dependency to some extent.
EQ Type 4 builds on Type 3, using a far greater Gain / Q dependency which maintains an almost equal area under the curve in the boosted region with gain control operation. It is extremely soft and gentle in use and is most suited to overall EQ fill and character modification for mixed parts (and completed mixes) where subtle changes in overall impressions are required. Therefore it will also prove useful in mastering situations where there is requirement to match the sounds of tracks from different sources on a common production release.
In the Oxford EQ, the highest and lowest bandpass sections can be independently switched to provide a shelving function. 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 persuasions.
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 ‘undershoot’ 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 Oxford EQ provides the facility to modify the response in this region, and so 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 example, the red plot shows a 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 its 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 an overshoot of half the total boosted gain, ie. for +20dB total HF boost the maximum loss in the overshoot region will be -8dB. The curves are symmetrical in cut and boost gain settings.
In addition to the four Oxford R3 EQ types, a further GML 8200 emulation EQ is provided, currently only for Pro Tools TDM and AAX DSP.
With the GML EQ, the Q controls in the LF and HF sections are inoperative when shelving is selected. Any previous setting of the Q controls will be restored when the EQ is reset to any of the appropriate GML 8200 band pass or Sonnox Oxford EQ selections.
GML 8200 Response Curves
The response curves of the emulation are very accurately matched to the outboard analogue unit, giving all the character of the original GML 8200 EQ, but with the added bonus of full +/-20dB gain ranges. Also, the Sonnox Oxford EQ filter sections may be run whilst in GML mode for additional processing effects.
Characteristically gentle GML 8200 shelving curves with frequency range to 26KHz and with full +/-20dB boost and cut gain ranges.
GML 8200 Bandpass
GML 8200 band pass section responses, showing full frequency ranges from 15Hz to 26KHz with +/-20dB gain ranges.
The plug-in’s user interface consists of two sections for EQUALISATION and FILTERING functions.
Displays the currently active EQ and filter response curves.
The LF and HF buttons switch the relevant filter in/out. The numeric button above determines the slope of each filter from 6dB – 36dB/octave in 6dB/octave steps. The rotary control determines the filter turnover frequency.
The FREQ control sets the centre frequencies for bandpass or turnover frequencies for shelf curves. The Q control determines the bandwidth of EQ curves, and sets the amount of overshoot function for shelving sections.
Two buttons to the left and right of the LF and HF gain controls select the shelving function for these sections.
The +/- rotary controls set boost or cut gains for each section.
The IN buttons enable individual sections of the EQ to be switched in/out.
Two complete EQ / filter settings can exist simultaneously. The A and B buttons allow you to toggle between them for comparison purposes.
This sets the attenuation level of the complete EQ section to avoid clipping signals when in boost.
The drop down menu lets you switch between available EQ types, as shown in the character display above.
This (just above the EQ Type window) displays any signal overload at the output of the EQ and Filter sections. This can be disabled via the Sonnox button menu (see below). When active, the default mode for this function is latching, requiring a click to reset. The options menu provides a mechanism to select the duration of the overload indicator.
Clicking the Sonnox button displays a drop-down options menu.
| Variant | 44.1/48 kHz | 88.2/96 kHz | 176.4/192 kHz | |
|---|---|---|---|---|
| 5-Band EQ & Filters | Mono | 17 | 8 | 4 |
| Stereo | 10 | 4 | 2 | |
| 5-Band EQ | Mono | 34 | 16 | 7 |
| Stereo | 19 | 9 | 4 | |
| 3-Band EQ | Mono | 42 | 20 | 9 |
| Stereo | 23 | 11 | 5 | |
| Filter | Mono | 33 | 16 | 7 |
| Stereo | 17 | 8 | 4 |
Sonnox Oxford plug-ins come equipped with their own onboard Preset Manager, which is displayed at the top of the plug-in window. The reasoning behind this is to allow increased portability of your presets across all the host applications, while also providing a consistent and versatile interface. While most host platforms allow creation and loading of presets, those host-created preset files are not portable between different host applications. With the Oxford plug-ins’ Preset Manager, you can create a named preset in one host application and load it when using an alternative application.
The Sonnox Preset Manager is fully described in a companion document — Sonnox Toolbar and Preset Manager User Guide — available for download at www.sonnox.com/docs
For latest System requirements, please visit www.sonnox.com.
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