What is Phase Cancellation?
Sound is made of waves of force that travel through the air. When they travel out from the sound source (the speakers), they push and pull the air molecules, creating shifts in the air pressure. When digitally mixing the left and right channels together, sometimes the low pressure part of one wave will line up with the high pressure part of the other wave. Since music is highly regular, this can cause consistent drops in your volume.
In Phase Audio- No dips in volume are happening here
Out Of Phase Audio- When the peaks and troughs of the audio lines up, there is complete silence or out complete phase cancellation
When is this a problem?This is mostly a problem when your music is played on mono systems like big PA sound systems, phones, and tablets. So if you use stereo sounds in your track, you should always check your song in mono.
To do this, all you have to do is throw on a utility plugin on the master channel and convert the track to mono. Every DAW will have an on board plugin that will convert any signal you pass through it to mono.
The best way to identify phase cancellation is by A/B'ing your sound, mix, or track in stereo and mono.
If there is a decrease in volume when you switch to mono, then your audio is out of phase or phase cancelling.
How To Fix Phase Cancellation
Let’s say you have an out of phase signal.
This phase cancelling could be caused by a sample that you are using, or it could be caused by a spatialization plug-in such as a delay or reverb, or an overlap of too many sounds.
Whatever the source of the problem is you have a few options on how you can fix this phase cancelling.
Fixing Phase Cancellation: Option 1
If you do have an out of phase sound, the first thing you want to do is change the phase of the left and right channels.
To do this, I recommend downloading the Voxengo’s PHA-979 utility plugin which is FREE!
Download the plugin here: Voxengo PHA-979
The PHA-979 plugin will help you identify where the phase cancelling is happening and give you the best tools to fix it.
Typically you would use a goniometer to get information about your sound's phase.
The PHA-979 uses an extremely intuitive read-out called a "phase correlation" meter. It tells you exactly how much phase difference there is for different frequency bands.
So the first option for fixing is again, to change the phase of the left and right channels.
You want the bars to be as high as possible towards the left side of the meter (the bass), while it's sometimes acceptable when the bars dip a little bit into the red on the right side of the meter (the treble).
Option 1- Adjust the left and right channels of the phase
This is what a signal that is in-phase looks like in the phase correlation meter or "Correlometer."
Fixing Phase Cancellation: Option 2
The other option is to add a slight delay to your left and right channels. Once again, we can use Voxengo’s PHA-979 to accomplish this. However, adding delay is a little bit trickier to deal with because the results can be unpredictable. I find that I need to add only very small delays, around 1 ms, to fix phase problems.
Sometimes the delay time that I need to add to a signal is smaller than the smallest tick available when turning the knob with my mouse. This is the only downside when using this option to fix phase cancellation.
Option 2- Adjust the left and right channel delay
Fixing Phase Cancellation: Option 3
Another option is to try going back to your sound source and finding the source of the problem. A/B your effects and look at the results in the phase correlation meter of the PHA-979.
Fixing Phase Cancellation: Option 4
Another option is to mix in a mono version of your track to bring up the power level.
Use your ears to determine the optimum amount of side mix. Sometimes you will only hear a power loss in certain notes, or in certain frequency bands. If there is a lot of dynamic variation in your sound, this could be a better option than narrowing your sound too much. Trust your feelings and make it your art!
Fixing Phase Cancellation: Option 5
Your final option is to decrease the side mix on your sound.
You should use this option till last as it will make your sound narrower and less defined in the stereo space.
Voxengos FREE MSED plugin can help reduce stereo width. All you have to do is lower the gain on the side of the gain knob on the plugin.
Phase cancellation is a common problem in todays mixes and can destroy the quality of your track.
This problem must be dealt with in order to compete with the mixes of today’s commercial tracks.
By using any of the 5 options above, you can give the clarity and power back to your tracks and avoid phase cancellation