This is a really short one, but even after the invention of one button magic plugins and sophisticated metering, it’s still one of the fastest method for correcting some mix problems.
Reverse the polarity
This is the fastest way to detect and solve problems with your ears and cost no nothing, and as a real bonus, can be done in a few seconds easily. It is a general advice because it works great both in post and music production. I know we have many fancy plugins that can detect, show, correct, suggest solutions, but some of them really just a nice GUI with no real value, some cost too much, some eat huge amount of CPU power.
In my opinion, don’t waste your money and time. Use what you already have, your ears and some free plugins.
Just a few examples, you can find these plugins in all Pro Tools versions (Native, HD, etc.) for free:
- trim plugin
- any stock Avid EQ
- Avid channel strip
Post production example
During dialogue editing, reversing the polarity on one track can help you filter out duplicate tracks (contain the very same thing), and detect issues in multi-miked situation.
During the sound design stage, we often layer many sounds on top of each other, sometimes this can be problematic. If suddenly you hear that your layered effect starts to sound too thin, you might have some problem with the phase. Just quickly flip the polarity switch on a plugin which is on the last track (last sound you just added) and listen if it solve your problem. Many times it does.
During the mix stage, when everything comes together and you constantly mixing in tracks, sometimes you might detect strange issues such as the well-known “head twisting” effect, or suddenly your bass and low region is suspiciously and strangely empty, you might simply have to flip the polarity on one or on a few tracks.
There’s more occasion than I can mention. Multi-miked situation almost always has some problems. Even a drum kit miked up properly can have some issues. Or if you have two bass drum mics, testing the sound with the polarity switch is a good idea. It pays off very soon as your mix will sound much tighter, the stereo or surround landscape will be more defined and stable.
It can even help between different instruments as this might help separation. If you record something live (studio or stage) there’s the inevitable leakage from other sources. This is generally not a big deal if it is under control, and more importantly if it don’t screw the instruments phase relationship too much. Sometimes, again, a polarity switch can solve these issues too.
What to listen for
It’s very easy really. You can even test it yourself with an old session where your deliberately force instruments to be out of phase.
The first thing to listen for is the low and bass regions. Every time you hear more healthy low and/or bass, you’ve found the right setting. Probably one of the most obvious example would be a snare drum miked both from the top and bottom. Set both faders to unity and flip the polarity switch on the bottom track. Many times what you’re going to hear is that the snare will be much more punchy and healthy at the lower registers.
The second thing sometimes a bit tricky, but with a very short ear training it’s quite easy to detect without any serious device. This is the “head twisting” effect. I bet once you hear it you’ll know what I’m talking about. It really feels like your head automatically want to turn into different directions. With just one button (you guessed right: the polarity switch) you can solve the issue.
This is a very easy and old thing, but often forgotten. It is so basic that we often forget the whole thing, while it can easily ruin a mix. Don’t afraid to test this, it takes only a second and you might solve many issues with it.