The position of a signal (waveform) in time is referred to as the phase and is measured in degrees. Much like the degrees of circle from 0 to 360.
Signals that are out of phase with one another will cause a varying degree of phase cancellation creating a loss in sonic material. There are multiple ways in which you may experience some phase cancellation problems.
Some common areas where phase cancellation often occurs:
1. Signal summing. 2 or more tracks being output through the same track within the DAW.
2. Mono compatibility. A stereo track when converted into mono.
3. Acoustics.The physical interaction of air molecules from the speakers to your ears directly and via reflections from surfaces in the room.
When you “sum” a signal, you are generating one signal with multiple combined signals. Signal summing can happen at various stages of the production process. Here is a list of a few of them:
a. Using instrument racks and drum racks. Having multiple sounds contained within a track must be carefully considered. When more than one instrument is being played, the combination of those sounds will ultimately be summed at the tracks output.
b. Using mono converting devices. If a stereo track has too much width, using a device that sums the left and right channel will create a narrower signal.
See the “Stereo vs. Mono” blog post for more information on this topic!
c. Using tracks that share the same band of frequencies. There will always be frequencies that are played simultaneously, this is what gives music its layered textures and stereo width. When summed at the master, the combination of these sounds will be produced through the left channel and the right channel.
All tracks output to the master channel and are therefore summed to produce the entire context of the production. In a classic case of phase cancellation, if the kick drum hits while the bassline is present, there is a varying potential for cancellation. Full cancellation may occur when two identical frequencies are generated at different phases and partial cancellation may occur when two slightly dissimilar frequencies are being generated.
To correct this particular problem, you may use sidechain compression to enable the bassline to “duck” below the kick drum when it hits.
In the low end of the spectrum it is common practice to keep those frequencies as mono sources but as you move up the frequency spectrum you may begin to exercise the stereo field more.
Although correcting phase problems in your mix is of the utmost importance, it also should be noted that stereo width can be achieved not only by panning but also by introducing partial phase cancellation between the left and right channel. If you wish to narrow the width of a wide stereo sound you may begin converting it into mono. Doing so will narrow the width but as a byproduct, the sound may begin to lose its integrity, texture, amplitude, thickness or depth. Converting a mix into mono allows you to detect phase cancellation where it should not be. This technique is common practice amongst producers and engineers worldwide.
The interaction of sound within a space can create some phase cancellation. For instance, in an untreated acoustic environment, you may experience a loss in amplitude when moving around a room listening to a particular band of frequencies. Using monitors in an untreated room will represent a different sounding mix due to reflections of nearby surfaces. Professional headphones or a treated environment with tuned equipment are the best places to avoid acoustic phase cancellation.
Partial phase cancellation: Total phase cancellation:
To conclude, phase can be your friend and your foe. It’s about finding the best balance between them both that makes for the best product.