Configuring an EQ plugin to function like a mixing console EQ section

Hi I am Chris Farrell from Western Australia. The following lesson is for week 5 of Introduction To Music Production at Coursera.

In today's lesson I'll be configuring an EQ plugin (WaveArts TrackPlug) to function like a mixing console EQ section. I've chosen the Solid State Logic (SSL) 4000 G Series mixing console to base my EQ plugin settings on, which was a very popular mixing console in the 80s.

The SSL console's EQ section

The EQ section on the particular console I'm referencing (with SL611G module) comprises of a four band parametric equaliser plus high and low pass filters. Here are the specifications of each filter in the console's EQ section:

• Hi pass filter: 0 - 350Hz with 12dB/octave slope
• LF (low frequency) band: a 12db/octave low shelf filter with a range of 30Hz - 450Hz, and boost/cut control
• LMF (low-mid frequency) band: frequency adjustable from 0.2 - 2.5Khz, with a Q of 0.5 - 3*, and boost/cut control
• HMF (high-mid frequency) band: frequency adjustable from 0.6 - 7Khz, with a Q of 0.5 - 3*, and boost/cut control
• HF (high frequency) band:  a 12db/octave high shelf filter with a range of 1.5kHz - 16kHz, and boost/cut control
• Low pass filter:  3Khz - +12Khz with 12db/octave slope

* Note this filter's bandwidth (Q) roughly corresponds to a range of +2 octaves (0.5) to about half an octave (3)

Now that we have a general idea of the SSL console's EQ bands and filters we can start to recreate this in a software plugin.

High pass filter

A high pass filter is used to remove frequencies below a sound's fundamental frequency which don't contribute to the sound and tend to muddy up a mix - such as noise, rumbles and vibrations.

In my EQ plugin TrackPlug I'm going to add a new Highpass band with a 12dB/octave slope, and set the cutoff frequency to 20Hz. Later when I'm mixing I'll be able to adjust the cutoff frequency to adjust where the low frequencies will start to be cut from. Note that TrackPlug doesn't allow me to specify the filter slope but it is set at 12db/octave in the plugin. To match the operation of the SSL4000G I would adjust the cutoff between 0 and 350Hz during mixing.

LF band (low shelf)

A low shelf filter can be used to boost or cut the low end - for example you might want to cut lower frequencies from guitar and vocals to make room for bass guitar. Shelving filters are gentle and provide a uniform volume shift beyond the cutoff frequency, unlike a hi pass or low pass filter which have a progressive volume shift.

In TrackPlug I'll add a new Lo Shelf band, set at 30Hz. TrackPlug doesn't allow me to specify the slope which is set at 12dB/octave automatically, but I'll be able to adjust the cutoff frequency and also whether a cut or boost is made (by adjusting the height). To match the operation of the SSL4000G I would adjust the cutoff between 30 and 450Hz during mixing.

LMF band 

This is a mid-range parametric EQ band which can be useful to remove unwanted resonances. It's always better to cut when adjusting in this range to avoid phase problems and distortion.

I'll add a parametric band with a Q (bandwidth) of around 0.5 octaves, and a cutoff frequency around 300Hz. Later I'll be able to adjust the cutoff frequency, height (boost or cut) and width (Q) to target any unwanted resonances. To match the operation of the SSL4000G I would adjust the cutoff between 0.2 and 2.5Khz.

HMF band

Like the LMF band, this is a mid-range parametric filter and can be useful for removing unwanted resonances.

I'll add a parametric band with a Q of around 0.5 octaves, and a cutoff frequency around 2000Hz. Later I'll be able to adjust the cutoff frequency, height (boost or cut) and width (Q) to target any unwanted resonances. To match the operation of the SSL4000G I would adjust the cutoff between 0.6 and 7Khz.

HF band (high shelf)

A high shelf filter can be used to boost or cut the high end to add brightness, particularly used on an element that you want to focus on in the mix. For example you could apply a high shelf boost to a vocal, while applying a high shelf cut to competing instruments, to bring clarity and focus to the vocal.

In TrackPlug I'll add a new Hi Shelf band, set at around 3500Hz. TrackPlug doesn't allow me to specify the slope which is set at 12dB/octave, but I'll be able to adjust the cutoff frequency and also whether a cut or boost is made (by adjusting the height). To match the operation of the SSL4000G I would adjust the cutoff between 1.5 and 16Khz.

Low pass filter

The final filter to be added is a low pass filter, and although probably used more rarely than the others is can be useful to remove all frequencies above a cutoff frequency.

In TrackPlug add a new Lopass band, and set the cutoff frequency to 20kHz, and I've bypassed this band so it's not active. Later when I'm mixing I'll be able to adjust the cutoff frequency and also the amount of cut or boost. Note that TrackPlug doesn't allow me to specify the filter slope but it is set at 12db/octave in the plugin.

Saving a preset with these settings

In my DAW, Presonus Studio One, I can click on the Preset menu item above the plugin GUI and choose "Save Preset As" to save a new preset. I've called it "Mixing EQ - SSL4000G" and I'll be able to load this preset whenever I want to start mixing with EQ bands similar to the famed SL 4000 series:

Putting it all together

To put this preset into practice I've loaded a vocal recording into my DAW and changed the EQ settings in the following way:

• Hi pass filter: changed cutoff to 46Hz with -24dB cut to remove noise and rumbles
• LF band (low shelf): changed cutoff to 345Hz with a slight cut to give other instruments (guitar, bass, kick) slightly more room
• LMF: bypassed
• HMF: bypassed
• HF (high shelf):  slight boost at 1.5Khz to make vocal sound brighter
• Low pass filter: bypassed

As you can see the lower frequencies are cut from the vocal while I've boosted the top end to make it brighter - this should allow the vocal to sit better with competing instruments like guitar and keys.

Conclusion

Today you've seen how to transfer the EQ section capabilities of a large format mixing console such as the SSL 4000 G series to a software EQ plugin - and save the settings as a preset to use as a starting point for general tracking EQ.

I hope you've enjoyed reading this and have learnt something, and feel free to let me know if you saw any errors. Note that I don't own an SSL4000 G series but I researched mixing consoles and found the user manual for the SSL 4000G and thought it would be good to base my assignment on this console. Apparently they claim that the 4000 series has had more platinum selling albums mixed on it than all other consoles combined.