Driver Troubleshooting; Verifying Driver Polarity - Meyer Sound MTS-4 Operating Instructions Manual

Driver Troubleshooting

Troubleshooting with TPL
The TPL LED can indicate serious driver problems, if
interpreted correctly. If one MTS-4 in a system exhibits
substantially more TPL activity than others receiving
the same audio signal, then one or both drivers in that
unit may have a short circuit. This is a potentially
dangerous condition for the electronics; shut the MTS-4
down immediately.
The TPL circuit does not activate if there is no power
dissipation in the driver, regardless of the input signal
level. Therefore, if all MTS-4s in a system receiving the
same audio signal exhibit TPL activity except one, then
that unit may have an open voice coil; disconnect it and
contact Meyer Sound for repair information.
NOTE: The Remote Monitoring System (RMS) provides
precise information about peak power, peak voltage, and
average voltage (VU) for each amplifier channel, enabling
a more complete driver diagnostic than the TPL LEDs.
Contact Meyer Sound for more information about RMS.
Driver Replacement
To determine whether the high or low drivers are func-
tioning properly, or replace a damaged driver, contact
Meyer Sound to obtain the Low Driver Inspection and
Evaluation Procedure for Self-Powered Series Products
(part # 17.010.120.01) or the High Driver Inspection
and Evaluation Procedure for Self-Powered Series
Products (part # 17.010.120.02).

Verifying Driver Polarity

Incorrect driver polarity impairs system performance
and may damage the drivers. All Meyer loudspeakers
are shipped with the drivers in correct alignment. How-
ever, if the driver or circuit wiring has been removed or
disassembled in any loudspeaker in a system for any
reason, it is essential to check the polarity between
drivers in the same cabinet and between adjacent loud-
speakers.
We do not recommend using phase poppers to analyze
driver polarity. The phase response for all drivers varies,
to some degree, over the frequency range in which it
operates. Since the phase popper, a popular but inaccurate
tool, does not discern variations in phase response with
respect to frequency, it provides no useful information
about the phase response through the crossover, the
most important consideration for determining correct
driver polarity.
10
Phase poppers are, therefore, not useful for performing
phase measurements on an individual loudspeaker or a
full-range sound system containing one or more cross-
overs. If necessary, apply a phase popper only to loud-
speakers with identical drivers without a crossover, and
check the system's overall phase response with a
frequency analyzer and/or listening test.
NOTE: Since polarity reversal causes excessive driver
excursion at high source levels, use moderate levels for
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 12"
and 15" drivers.
2. Connect a signal source to the loudspeaker and note the
frequency response.
Drivers with correct
polarity cause acoustic
addition
The polarity is correct if the frequency response is smooth
through each crossover region (40 Hz, 100 Hz, 1 kHz).
Cancellation greater than 6 dB in any region indicates
polarity reversal between the drivers on either side of
that crossover point.
Polarity Between 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. Broad-
band cancellation (decreased overall level) indicates
polarity reversal.
NOTE: Polarity tests among more than two speakers may
damage the drivers in the cabinet with reversed polarity.
This driver is 180 ° out of
phase to the other drivers
Drivers with reversed
polarity cause acoustic
cancellation