Whether it’s vocals, speech or instruments – these days you’ll hardly come across audio that hasn’t been processed in some way. Even a small amount of EQ can help a voice stand out by emphasising presence. We generally distinguish between effects that simply optimise the signal and more creative effects that audibly transform it. Signal processing is as old as recording itself – but it’s far more affordable today than in the days of huge plate reverbs hidden away in studio basements. Alongside “specialist” devices, there are also multi-effects units that combine several effects in one piece of gear.
Designed for different tasks, these devices help keep volume levels under control. In the most extreme case, a limiter can cap the level at an event or within a venue area. Some processors such as the Behringer MDX2600 V2 (PAH0020550-000) offer additional options beyond limiting for processing mono or stereo signals – including expander, gate and de-esser.
This limiter is officially approved and allows the configured “sound wall” to be sealed, preventing any debate about the permitted volume level.
On loud stages – where the risk of feedback is highest – feedback destroyers detect runaway frequencies in a fraction of a second and eliminate them automatically. Some devices analyse the mix continuously to react to emerging feedback, while the filters are adjusted automatically. Depending on the model, multiple frequencies can be suppressed at the same time.
Crossovers are used to split the full frequency spectrum into separate ranges and route them to the appropriate loudspeakers. A subwoofer, for example, handles only low frequencies and doesn’t need to reproduce mid or high content. This takes strain off the midrange and high-frequency drivers and results in a clearer, more precise sound, allowing each speaker to play to its strengths.
Example crossover: Behringer CX2310 V2
Almost everyone has used an equaliser at some point – consciously or not – whether on a home hi-fi system or in the car. In simple cases, these feature two or three controls for specific frequency bands. On mixing consoles, EQ sections are usually more sophisticated. A 3-band EQ often allows the mid frequency to be adjusted, which is then referred to as a parametric equaliser. A classic SSL console additionally provides separate controls for high-mid and low-mid ranges.
31-band graphic EQ in action: Behringer FBQ3102HD Ultragraph Pro
A graphic equaliser is one where the frequencies are fixed and laid out as a row of sliders. This makes the frequency curve easy to read visually – hence terms like the “smiley EQ”. Graphic equalisers are often placed at the end of the signal chain, directly before the power amps, to adapt the sound to the room acoustics. A so-called master EQ is often used to correct boomy bass frequencies in the overall mix. In addition, there’s usually a low-cut filter that removes low frequencies below a defined threshold entirely.
This DBX 231S equaliser offers 31 bands per channel to tailor the sound of a stereo mix optimally to the room and PA system.
If you’re looking for a live mixing console, you’ll usually choose a model that already includes all the common effects. But even outside the console – for example directly on stage – standalone multi-effects units are often used to shape the sound more precisely.
While the specialist devices mentioned above are more suited to the overall mix, other multi-effects are used directly with an instrument or microphone. Vocalists can add harmony voices, reverb or distortion to their signal. Effects such as chorus or compression are also available, helping deliver a finished, balanced signal to the engineer – particularly useful if they haven’t worked with the band before.
Multi-effects for flexible sound shaping: Behringer Virtualizer