Instead of HPF/LPF, try shelves
Sometimes there’s too much information at the very low end or very high end of a sound, and we need to deal with it. Kick drums might have a bit too much sub information (or not quite enough), cymbals might have too much fatiguing high-end garbage, etc.
I think a lot of us learn early on that the “correct” way to deal with extraneous information at the extremes of the frequency spectrum is with highpass and lowpass filters (HPF/LPF). And it makes intuitive visual sense, right? LPFs and HPFs cut things off. Which is what we think we want.
But HPFs and LPFs do something else, too: they mess with the phase response of the sound in question pretty severely. And they don’t just mess with the phase of the signal on the inside of the cutoff point; they mess with it outside the cutoff point also!
Check out the below picture; see how the phase response of a HPF is 45 degrees at the cutoff point, with half of the frequency shift happening above that and half below?
What this means in practice is that your sound can get kind of “mushy” in this area. Sometimes that can be a plus! Phase shift in the high frequencies in particular can result in a gorgeous “smearing” kind of effect, kind of like portrait mode on a photo.
There is also a potential downside to phase shift, though, which is that your transient definition can also get smeared. This can result in sounds losing their impact / solidity / definition. In the example of the kick drum, that can be problematic for some fairly obvious reasons!
So here’s my little hack: instead of HPFs and LPFs, use shelving EQ.
On the low end, one of my favorite tricks is to do a low shelf at 40 Hz, and then sweep the EQ gain until the amount of thwomp is precisely where I want it. (This also works great on bass synth and bass guitar, both of which often have way too much sub-bass in them.)
On the high end, a shelf in the 10-12k Hz area can provide some gorgeous contouring and definition to keyboards / drums / guitars / cymbals, while retaining much more of the definition that allows those parts to speak clearly.
Check it out for yourself and see what you think!
Shelving something can actually be a good thing — jamie
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