FRONT OF HOUSE
POLARITY AND PHASE | Kent Morris
One of the basic aspects of live sound is between. Polarity, as in “polar”, is either positive are attenuated while others are accentuated. A
electrical transfer of signals. Once an acoustic state first or negative state first. It’s north or circle has 360 degrees, so we can experience
input is captured and converted into electricity, south. The signal either starts in the positive a 35, 78 or a 90-degree phase shift, depending
it remains in this state until reconverted to aspect or the negative aspect. One positive on the relative positions of the inputs. A simple
acoustic energy by the loudspeaker. While and one negative of the same wave will result experiment to hear phase shift is to take two
electrical, the concepts of polarity and phase in complete cancellation. Polarity can stand similar mics and speak into them through the
come into play. It seems simple enough: when alone with a single wave and does not include sound system while varying their distance from
the mic sounds odd, flip the “phase switch”. the element of time. Phase, on the other hand, one another and the source.
But what does that mean exactly? And, what is offsetting two waves in time. This interaction
is the difference between polarity and phase?
Finally, how can you use polarity and phase to
correct issues in live sound?
4. Phase shift is also possible without
microphones. The most common example
Polarity can
here is when a dual line signal, say a stem track
output from an iPad, is collapsed from stereo to
Here are some answers:
1. On a mixing console, the function labeled
phase, polarity or simply 0 is taking the hot and
cold leads of a balanced input and reversing
them. On an XLR, this would be flipping pins 2
(hot) and 3 (cold). The purpose of the switch is,
for instance, to correct the error that will occur
naturally when a snare drum is mic’d top and
bottom. Since the mics are focused in opposite
positions, the resulting combined signal will
have loss of definition and certain frequencies.
Positive push on one is equal to negative push
on the other, so they are polarity inverted.
Engaging the polarity switch (it should not be
called “phase”) on the lower mic puts it back in
sync with the top mic.
2. Inverted polarity can sometimes be used
creatively to solve other problems. The most
common old-school example here is with
stand alone mono with a cable adapter. Stereo tracks are
with a single when brought to mono, but that is not always
supposed to preserve their frequency response
the case. The solution is to use a proper
wave and does
interface from Radial Engineering or similar to
transfer the signal without degradation.
not include the 5. Speakers use two wires to carry the signal
element of time. can be accidentally reversed. When this
Phase, on the
from the amplifier. Since there are two, they
happens, there is a loss of low-end response
and definition in the sound. The old way to test
for proper polarity was to connect the speaker
leads to a 9 volt battery and watch whether
other hand, is the cone moved forward or reverse when
offsetting two several handheld testers on the market and
waves in time.
floor monitors, where the monitor send signal
connected positive to positive. Now, there are
even some apps to confirm polarity is as it
should be.
To recap, polarity is a wave in positive first or
negative first orientation while phase is a time-
is inverted relative to the mains send and the results in partial cancellation and partial based correlation between two or more waves.
outcome is significant cancellation between the reinforcement of each wave. If two microphones While simple, these two concepts can either
two. The result can be increased gain before are set to pick up a person speaking and one is greatly enhance or diminish the overall sound
feedback, but the side effects are rather severe, a lapel mic while the other is a lectern mounted quality of any system, so it makes sense to be
so other solutions are typically employed now, mic, the time and level offset between the two certain the console polarity switch is in the right
including the use of microphones with better mics will create audible phasing when they are position and the mic and speaker cables are
rejection characteristics, digital loudspeaker combined in the sound system. One mic is terminated properly.
management systems and in-ear monitors. physically closer than the other, so it receives
the signal first and then the second signal is
3. Polarity is yes or no; phase is all the maybe in
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delayed relative to the first. Some frequencies
March 2019
Kent Morris
Kent is a 40-year veteran of the AVL arena driven by
passion for excellence tempered by the knowledge
digital is a temporary state.
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