In the beginning there were volume knobs, and that was good. Then came bass and treble controls, and that was better still.
But more was wanted, so more was created and thus the equalizer was born. Over time, equalizers have been shaped and honed into the various formats that are ubiquitous today.
Graphic, parametric, semi-parametric, paragraphic, and more – such as Lake’s rather brilliant Mesa filters – entered the market years ago and we can’t seem to get enough of them. At last count, retailer Sweetwater has 70 different models in it’s catalog, with GC Pro offering an even larger portfolio.
How do we sort them out? It starts by matching EQ types to EQ tasks. The use of equalization falls pretty squarely into four primary processes – let’s call them layers – that they’re expected to perform. It’s important to approach these layers in a logical order.
Room. The first layer should always be correcting low-frequency room resonance and any other room-related issues. Usually, this is best accomplished by means of a loudspeaker management tool that includes a generous bank of user-adjustable EQ filters, as most now do. This layer is the foundation that everything else is built upon.
Loudspeakers. The second layer is likely to be far less linear than a console, power amplifier, cables, most microphones, and so on. Even top-shelf loudspeaker systems will rarely be the flattest ruler in the tool box, so this is the layer in which we solve frequency and phase response problems, fix misalignment in the time domain, and integrate the mains with the subwoofers.
Fortunately, modern DSP-based loudspeaker controllers offer a wide selection of corrective tools, enabling precision alignment. Such tools include an extensive range of filter types, incremental delay, protective limiters, and more.
It’s important to note that if a given loudspeaker system is seriously deficient and nowhere near flat, it needs to be addressed first, then the room, then the loudspeaker system one more time. Don’t mistake room resonance for loudspeaker performance problems.
Instruments, Microphones & Vocals. The third layer is tailoring the sound of the vocals and instruments to support the style of music in consideration of what the artist wants to achieve. We add filters to suppress feedback, make that piano, sax, or Sousaphone sound like it’s meant to sound (and/or whatever sound is appropriate for the mix), and shape the overall aural “feel” of the show.
Vocal tonality should flatter the vocalists, instrument tonality should flatter the instrumentalists, and everyone needs enough gain-before-feedback to be clearly heard and understood. If the event includes track playback, then tracks should be given the attention they might need to satisfy the desired production values.
This layer can usually be handled by channel EQ on the console, but outboard devices – graphic or parametric, depending on what you’re comfortable using – can be very useful for taming difficult sources such as podium mics, lavaliers, strings, grand pianos, vibes, xylophones, poorly recorded tracks, and any other source that requires more sonic shaping than the channel strip is able to provide.
Preferences. When the other layers are firmly in place, you may wish to make tonal changes that are purely preferential at the start of sound check. This may be a one-time thing, or it may vary from moment to moment.
Perhaps the guitarist demands an unusual tonality for a certain solo part that defines his signature sound and needs help to obtain it. Maybe the vocalist performs in a wide range of styles and wants to come across differently from one tune to the next (think David Bowie). Or it might be as simple as occasionally compensating for changes made on stage, such as swapping out a guitar or horn.
In any case, preferential EQ changes should ideally be programmable from console presets, or if that’s not available, then programmable from outboard equalizer(s) so that the baseline EQ can always be found again and reverted to. Preferential EQ should never compromise the system’s overall linearity.