Phase Cancellation: A Pocket-Guide to Phase Cancellation and How to Fix It

Understanding phase cancellation came was mini revelation for me. You don’t even have understand the theory behind to actually hear the difference

So, what happens when you have phasing issues?

  • Dull and flat sounds
  • Decrease in amplitude
  • Become weak and brittle not strong and powerful

The image below shows two signals that are complementing each other. As you can see both waveforms are identical.

what is phase cancellation in music?

This is where the two wave forms are ‘in phase’ – When the positive and negative peaks of both wave forms line up with each other it’ll give the sound a bigger and more thicker sound..

However, what happens when the peaks of the wave forms don’t line up with each other?

Phase cancellation happens when you have two similar or identical sounds or signals cancelling each other out when they move out of ‘phase’ or work against each other.  

The more the waveforms work against each other the lower the amplitude and the duller the duller sound becomes.

Complete phase cancellation is when the negative waveform from one signal directly mirrors the positive signal of the other.

As you can see from the new image each waveform is almost a complete mirror of one another. This is when phase cancellation happens. The sound coming from this now would be the opposite of the first image and there would be silence and no audible tone.

 

Why? Here’s a great video to help your get your head round the concept;

Key Moments:

  • 52: What a basic sin wave looks like
  • 41: The horizontal line in a wave form (AKA zero-point crossing / the neutral point)
  • 53: Anything above that line is positive signal
  • 59: Anything below the line is a negative signal
  • 21: What is phase cancellation? Two ‘tracks’ that are shifted out of ‘phase’ with one another.
  • 30: ‘In Phase’ Example – notice how the amplitude increases when they are both combined and complement each other.
  • 48: How do they get or move out of phase?
  • 27: Phase Cancellation Example – notice how the volume has dropped significantly
  • 15: How to do a comparison
  • 45: What 360, 90 and 180 degrees mean when talking about phase cancellation
  • 47: the 3 in 1 rule
  • 30: Mono compatibility vs phase cancellation

Layering Sounds

So how does this relate to the real world when you’re producing music?

Well lets take a kick drum sample for example. Maybe you want to ‘beef’ the kick up a little so you find another kick drum sample that fits well with the sample.

If the opening transients of the each kick drums go off in opposite directions (that is, one going towards positive while the other simultaneously goes negative) you might end up with phasing issues.

The chances of getting completely silence are rare but if you wanted to add more ‘meat’ to your kick drum and you’ve got a phasing issue actually end up with a kick that sounds less ‘beefy’ that what you started out with.

Again, this can affect any layered sound.

How to identify phasing issues in your mix

Using your ears to hear dull and flat points in your track is by far the best way to ‘search and destroy’ any phasing issues that might going on in your mix.

Sometimes these phasing issues will be as bright as day – sometimes they won’t.

A good habit to get yourself into before mixing your tracks is to solo everything in your mix and listen. So you could;

  • Solo and play just the drums section of your mix
  • Then repeat for all the other sections of your track
  • Then, solo each of the instruments in your mix (Kick drum, Snare, Hats, Keys plus any layered instruments etc)

While you’re doing this you’re looking for a couple of things.

  • Firstly: Your listening to instruments in relation to each other. So how does your kick drum sound in relation to your snare and hats for example
  • Secondly: You’re listening for the relationship between your layered instruments

While you’re doing this here are a few questions to ask yourself;

  • Does this sound like I want it too sound?
  • Does it sound like it should sound?
  • For my layered sounds – are they loud and thick or are they flat and dull?

And if you want to do a more in depth inspection – zoom in on the waveforms of each sound that don’t seem to be sounding right and compare them; Does each waveform mirror each other? In other words –  do the negative and positive peaks go in opposite directions?

If they do – then you have phasing issues.

How to Fix Phase Cancellation When Mixing

One way (and the most popular way) of dealing with your phase cancellation issues is to invert the polarity of the one of the samples. Since the resulting sound is almost identical it doesn’t really matter which layered sound you invert.

When you invert the polarity of the selected waveform you’re essentially ‘flipping’ the waveform. Usually a quick press of a button and that kick drum layer that was sound poor, weak and dull all of sudden sounds like a beast.

Sometimes though, polarity inversion won’t work.

If you watched the video above you’ll notice that if the waveform fall on a 90 degree – flipping or inverting the polarity isn’t going achieve much.

So you might have to play around with the polarity and edit the position of the waveform to get the sound you’re really looking for.

Save yourself some money

There are some paid plugins that offer polarity inversion plus a few other features that might come in handy – but for the most part, all top level DAW’s should have a polarity inversion option.

So as you can see phase cancellation really can be the silent killer in your mix. And if it’s something you didn’t know about before you certainly do now.

What’s important to remember is that whenever you are layering sounds whether that’s a kick drum or some leads – listen carefully and if the sound doesn’t create the feeling or punchy you were looking for, take a deeper look ‘under the hood’ and inspect the waveforms.