The nebulous Q setting in EQ. Is it the “qualization” of equalization? Not exactly… so what DOES it do, and where should we typically set this important EQ setting? Here’s everything to know about the Q setting in EQ.
Q Setting
The Q setting affects the width of an EQ band/adjustment that you make in your EQ plugin, relative to the surrounding frequencies.
Depending on the type of EQ filter you use, the Q will have a slightly different effect.
Above pictured is a bell shape in FabFilter’s Pro-Q 3 EQ, making a 3dB cut at 500 Hz with the default Q of 1.
Generally speaking, a lower or smaller Q setting will yield a wider curve. You’ll notice with the Q at 1 in the image above, even at 500Hz as the nadir of the cut, frequencies below 200Hz and above 2k are affected to some extent.
If we drop the Q as low as it will go, you’ll see that 3dB cut affects roughly the entire frequency spectrum!
That’s a bit of an extreme example as typically a Q of 1 is gradual enough a transition to yield good results.
What if we want to get surgical in a cut, removing a very specific unwanted sound which is exclusively at 500Hz. The narrowest Q of 40 would look like this:
We need to be careful with making too many cuts like this, or we enter the realm of comb filtering as a result of moves we made ourselves!
So on a normal bell style band to cut or boost limited frequency ranges, the Q affects the width of that band. How does the Q affect different types of filters.
In high shelf EQ or low shelf EQ cuts or boosts, the Q affects both sides of the shelf point:
Similar to the bell filter, a lower Q results in a gentler and slower transition, affecting more surrounding frequencies.
With an aggressive, maxed out Q setting on a shelf, we pull from one side while simultaneously boosting the other side:
So instead of just affecting the frequencies on the shelf side of things, we’re aggressively taking from the other side, as well.
A Smaller Q Setting is Generally Better
While higher Q settings can be used to make surgical cuts, leaving the surrounding frequencies intact, you generally want to stick with average or lower Q settings.
As I’ve mentioned time and time again when talking about EQ in mixing, gentler and more gradual curves yield more natural and transparent results, also resulting in less phase issues.
If you find that your audio needs a lot of adjustments with an aggressive Q setting, you should identify what the issue was with that audio during the recording process so that you can correct it for the next time.