Mixing: Phase button first, EQ second
I’ll write a post on what polarity and phase are at a later point.
You import the drum tracks into your DAW, then balance the drum kit, only to notice that the kick drum sounds too thin.
STOP IT RIGHT THERE
Before reaching for the EQ to bump up the lows, use the stock gain plugin (Logic Pro X), or a stock EQ or Compressor (Pro Tools), or maybe it's right there on the channel strip (Reaper)
and click that button that looks like a zero (0) wielding a katana. I mean this one below:
Consider these two scenarios:
1. Your kick drum was recorded using 2 mics on it - inside and outside the drum; close and far, both outside; etc
2. Your kick drum was recorded using 1 mic on it, and it's in the overhead microphones as well.
Fixing the phase issues
The steps to fix the second scenario from above (or at least ameliorate it, see the link at the end of the article) are as follows:
- Solo the kick and overhead(s) channels
- If you have multiple overhead tracks, pan them to the center
- Adjust the volume on the tracks so that they're close to being the same. THIS IS VITAL, otherwise you might not hear any difference
- Insert a trim/eq/whatever plugin, one that allows you to flip the phase
- Flip the phase in and out and listen to the difference.
You're listening for a thicker, deeper low end.
It's easier to hear differences in the low end, than the top end. With experience, you'll be able to hear phasey top end as well.
Flip the phase on every drum track against the overheads, for example, and HEAR what sounds best. If you can't hear a difference, maybe you need to try nudging the regions a bit.
Another situation when you'll want to...
... check the phase is after re-amping bass guitar.
You listen to just the DI track, and it sounds full. Then you listen to the re-amped track, and it sounds amazing. Then you listen to both, and they sound thin and flimsy.
Usually, it takes time for the signal to travel from your interface into the amp, then into the microphone and back into the interface; this introduces phasing issues.
Flipping the phase on one of those two tracks could greatly increase the instrument's low end presence.
Last, but not least…speakers pushing or pulling?
Here’s something for the slightly more seasoned mixer: the polarity of the bass instruments affects how the speakers are moving. Understandably, this also changes the sound of the low end, especially if you’re listening on speakers.
It’s important to make sure that all the low end elements are moving the cones in the same direction. If the kick drum is pushing and the bass guitar is pulling, it can happen that they cancel each other, ruining your bottom end.
Checking the phase before doing any EQ moves solves many issues you might encounter.
Audiomere's Polarity Maximizer does this for you for all the mics on an instrument at once. At only $49, it's cheap and it saves you quite a bit of time at the beginning of any session. I highly recommend it.
Obviously, getting it right at the source is better than any plugin.
Further reading on phase and polarity
If you'd like to learn more about the science of phase and polarity, common situations when you need to flip the phase, and so on, check out this article on Sound on Sound.