Shelving Equalizer

In a shelving equalizer, all frequencies are boosted or cut by the same amount. But, to understand this, let’s first get back to basics. One describes equalizers in reference to a flat response curve. This means that a system or a piece of equipment responds evenly to all frequencies within a specific range. The range is typically set to 20Hz to 20kHz. However, one never applies shelving to a mid-range boost or cut. Rather, shelving varies from the high-frequency end of the spectrum to the low-frequency range of the spectrum.

Forms of Equalizers

Equalizers appear in many forms. Firstly, one of them involves the bell where the band is boosted. At higher and lower frequencies, the response tends to return to normal. Secondly, another form of EQ is the one that increases the response within a stable frequency and moves towards the high end of the spectrum.

When Does the Shelving Equalizer Come Into Play?

Shelving equalizers can apply to both high and low frequencies. They also concern cuts and boosts. These equalizers provide a peak/deep response on the side of the desired mid-frequency, as well as a flat cut or boost region. Specifically, you use shelving EQs to add brightness to the general sounds. A high-frequency shelving equalizer is not limited to a center frequency, nor to its associated bandwidth. As a result, there is a flat frequency response above the chosen frequency. Above all, the flat region that is beyond the center frequency increases or decreases.

More Specifics on the Shelving Equalizer

Because the transition back to the unprocessed region is always half of the bell curve of a peak/dip outline, the 3dB down point, the idea of bandwidth and the quality apply to the shelving equalizer. Boosting by 9 dB at 10 kHz and above translates into a 3 dB down (+6dB) at 10 kHz, which achieves the full boost at 9 dB. (That is, a little bit above 10 kHz.) Below 10 kHz, the shelving EQ might not be able to process the signal. Below 10 kHz, the it starts to lift the signal amplitude up. A high-Q shelf suddenly transitions from a region of unaltered frequency response to the region of the 9dB boost. In contrast, a low-Q increases that transition.

Shelving EQs: Conclusions

As you can see, shelving EQs are quite easy to use, but not that flexible. They are somewhat limiting, for they only alter the fundamental timbral qualities of a sound. Shelving equalizers work on bass and treble, which are located on both sides of the audio spectrum.

If you’re interested…

If you want to learn more on this topic, you can consult our entries on linear phase, dynamic, and parametric equalizers.