High shelf EQ is one of many types of EQ filters which can be used to uniformly boost or cut a frequency range higher than a starting point of your choosing. Let’s talk how to use high shelf EQ, its benefits, and how it differs from low shelf EQ.
High Shelf EQ
As I typically mention when talking EQ (grab my free EQ cheat sheet for a complete, comprehensive, but short guide on everything to know regarding using EQ in your mix), gentle slopes and smaller changes in gain yield the most natural and oftentimes the best results.
This is the basis of high shelf EQ when you want to boost or attenuate the higher frequencies in your mix.
High shelf EQ creates an upwards or downwards slope into positive or negative gain at the point of your choosing. That slope then levels off to create a flat and uniform boost or attenuation which resembles a shelf, hence the name.
Using a high shelf is great whenever we want to bring out more top end, like with vocal EQ.
If I want more vocal clarity with EQ, rather than nitpicking in boosting 8k, 10k, 12k, trying to bring out more air and crispness in the vocal, I just love a high shelf in that 8-12k.
Not only does a simple uniform boost like this cause less phase issues, it’s also easier to get quicker results that sound good without overthinking it.
You can then make a cut or boost within that shelf if you need to if something pokes out after you make that adjustment (another benefit of adding a high shelf).
High Shelf EQ Settings
The like other EQ filter types, the main things which affect shape of the shelf are the Q, slope, and gain.
The gain is straightforward – it simply affects how much gain you’re adding on average with the boost or cut.
The slope affects the grade of the that upward or downward slope to the shelf. A higher dB/oct creates a sharper and faster climb into that shelf/adjustment. A smaller figure like 12db/oct creates a more natural adjustment.
The Q has the greatest effect on the high shelf EQ as it controls the behavior of the frequencies on both sides of the EQ point.
In the above image, we have a default Q of “1”. This create a gentle and smooth transition up or down into positive or negative gain for that shelf.
If we max out the Q at “40” in FabFilter’s Pro-Q 3, you’ll see we get a considerably more aggressive and steeper break point at the EQ point, like a cliff.
Note only does this have an aggressive adjustment on the higher end, it has the reverse effect just below that EQ point.
On either side of the cliffs, the curve begins to smooth back out to flatness. If you need to simultaneously cut/boost above a point while simultaneously having the opposite effect just below it, a high shelf with an extreme Q like this works.
What if we turn the Q practically all the way down?
If we drop the Q to 10% of that, let’s say with a Q of “.1”, you’ll see that there’s virtually no difference between the grade before and after the EQ point.
The effect of this is the point to the left of the point will get pulled up or down sooner, making a more natural curve overall.
This yields a more transparent result, but at the expense of affecting the lower frequencies likely more than we want.
Generally speaking, the standard Q of “1” works well to create a gradual and subtle adjustment to emphasize or de-emphasize the higher frequencies with a boost or cut, respectively, via a high shelf.
The next time you decide you want more or less brightness, sharpness, or immediacy in that high end of a track, rather than completely rolling it off with a low pass filter, you might try a high shelf for a more subtle and natural sounding compromise.