Shelf bands on an EQ: a clarification · Mastering.com Members Club

Shelf bands on an EQ: a clarification

I noticed in the music production 101 course, there was some talk about EQ shelf filters, and how they boost a frequency "above a certain point". This isn't really true though, they also boost a bit (in a slope) below that point too. This is important, because if you're recording and mixing at a high sample rate (such that frequencies above 22.05kHz are not aliased), then using a plugin like the Maag plugins' air bands (or other analog emulations) at 20k or above can affect the frequencies below it in a really pleasing way.

I posted a comment somewhere nearly a decade ago about how recording and mixing above 48kHz is a pretty good idea, and people widely rejected that, claiming that "mixes are rendered at 44.1k and humans can't hear above 20, so there's no point!" but that ignores the fact that frequencies above 20k can actually have an effect on how the ones below it sound, and doesn't take aliasing issues into account. Fast forward 10 years and everyone else seems to be catching up on this fact (and oversampling too!), but I'd just like to point out that there's a reason mixes are exported at 44.1kHz and not 20! Because to give the minimum viable aliasing, you need double the max frequency (so 40k) but also provide a small buffer so that the top range of hearing isn't mangled by a 1-bit on/off aliased cycle, the minimum sample rate suggested is actually 44.1kHz, not 40, not 20. That's not an accident, and finally,

It's widely misunderstood that 44.1kHz is "all that's required" when actually, it's a bare MINIMUM requirement, for not exceeding the most possible damage to high frequencies that listeners can tolerate. However, 44.1kHz is still the maximum damage to those frequencies that users can tolerate. 48kHz is less, 92 even less and less and so on.

So higher sample rates = less damage to those frequencies, as is very apparent when using plugins or hardware that boost frequencies above 20k, especially in analog emulations.

4 comments