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Phase poppers are, therefore, not useful for performing phase
measurements on an individual loudspeaker or a full-range
sound system containing one or more crossovers. If necessary,
apply a phase popper only to loudspeakers with identical drivers
without a crossover, and check the system’s overall phase
response with a frequency analyzer and/or listening test.
!
Since polarity reversal causes excessive driver excursion
at high source levels, use moderate levels when conducting
these tests.
Driver Polarity in the Same Loudspeaker
Use the following test procedure to verify polarity between
drivers in the same loudspeaker:
1. Place a measurement microphone 3 ft from the front of
the loudspeaker at the midway point between the low
and high frequency drivers.
2. Connect a signal source to the loudspeaker and note the
frequency response.
Drivers with correct
polarity cause acoustic
addition
Drivers with reversed
polarity cause acoustic
cancellation
High driver is 180° out of phase
The polarity is correct if the frequency response is smooth
through the crossover region (600Hz – 1 Hz). Cancellation greater
than 6 dB in the same range indicates polarity reversal.
Driver Polarity In Adjacent Loudspeakers
Use the following test procedure to verify the polarity between
two adjacent loudspeakers of the same type:
1. Position two loudspeakers adjacent to each other.
2. Place a measurement microphone 3 ft from the speakers
on the axis between them.
3. Connect a signal source to one speaker and note the
frequency response and overall level.
4. Apply the same signal to the second speaker with the
first speaker still connected.
The polarity is correct if the frequency response remains constant
with a significant increase in amplitude. Broadband cancellation
(decreased overall level) indicates polarity reversal.