What is Phase and Why Does it Matter?
With almost endless audio articles out there on the web, you are sure to come across a term in the audio world called “phase.” Some information out there may confuse you more than clarify this important fundamental topic, so my goal is to make it as simple as possible.
I would personally define phase as simply the relationship between two or more waveforms. Phase is relevant to you whether you are an engineer, producer or artist. But Why?
Why phase matters, in and out of the studio:
When a waveform is added together with an identical, or near identical waveform, one should keep in mind that they are at risk of running into problems relating to phase. For example:
Here are two identical sine waves, perfectly “in phase.” The result is a louder output volume:
Next, I inverted the second sine wave leaving the two sine waves completely “out of phase.” The result here is complete silence due to 100% cancellation:
Lastly, here are two identical sine waves that are shifted slightly out of time:
This results in a reduction of volume.
Obviously in the real world, everything isn’t as simple as a sine wave. As a recording engineer, there may be many instances where you come across problems relating to phase. For example, if you are tracking a guitar amp with two or more microphones, the complex, harmonically rich waveform could potentially arrive at each mic’s capsule at different times. This difference in arrival time will cause a phenomenon known as “comb filtering.” Comb filtering is a sequence of constructive and deconstructive phase interference up the frequency spectrum.
For a mixing engineer or producer, a common occurrence of phase interference is when using sends and returns. For example, if you are bussing all of your vocals to an aux, and that aux track happens to have a CPU intensive plugin, this may create an offset in time between the two sets of waves if the delay is not properly compensated for. Most modern DAWs (Digital Audio Workstations) include a delay compensation engine, but it is important to be aware that this problem may occur to make sure you set proper compensation.
Why does phase matter to a performing artist or DJ?
You’ve shed blood, sweat and tears over your mix and it sounds great! But wait … you forgot to check it in mono? Who cares though, right? Mono is a thing of the past, you say! I say, hardly. If you’re an artist, DJ or producer that goes out there to get your music heard and heard right, then checking your mix in mono is very important.
The majority of live sound systems in venues across the nation are in mono! That’s right! But Why? Your fans should be able to enjoy your music as you intended it to be, whether they are standing to the left, right or center of the stage.
Checking the phase of your overall mix is quite simple. Throw a phase scope on the master bus and see the results. Phase scopes seem a little more intimidating than they really are. If your mix is in phase, the phase will read between 0 and +1, and will tend to be more vertical along the scope. If it is out of phase, it will be anywhere below zero, and more horizontal.
Shoot for above zero and you’re in the clear!
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