10
Driver Troubleshooting
The Remote Monitoring System (RMS) is the best method
to query the status of the drivers in a system before and
during the performance. RMS monitors peak power,
peak voltage, and average voltage (VU) for each amplifier
channel, allowing immediate detection and muting for
drivers with open or shorted voice coils, with minimal
disruption to the system. Contact Meyer Sound for more
information about RMS.
In the absence of RMS, several methods can be employed
to obtain information about the state of the drivers.
Troubleshooting with TPL
The TPL LED can indicate serious driver problems, if
interpreted correctly. If one PSW-2 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 PSW-2
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 PSW-2s 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.
Driver Replacement
To determine whether a driver is functioning 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).
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.
NOTE:
Since polarity reversal causes excessive driver
excursion at high source levels, use moderate levels for
these tests.
Driver Polarity in the Same Loudspeaker
A cabinet with two identical drivers receiving the same
input signal produces an extremely low amplitude output
signal if the polarity of the drivers is reversed. Use the
following test procedure to verify the polarity between
drivers in the same loudspeaker:
1. Place a measurement microphone 3 ft from the
front of a loudspeaker that is known to be wired
correctly, at the mid-point between the two drivers.
2. Connect a signal source to the loudspeaker and
note the frequency response and overall level.
3. Place a measurement microphone 3 ft from the
front of the loudspeaker with unknown polarity,
at the mid-point between the two drivers.
4. Connect a signal source to the loudspeaker and
note the frequency response and overall level.
Drivers with correct
polarity cause acoustic
addition
Drivers with reverse
polarity cause acoustic
cancellation
This driver is180
°
out of phase
The polarity is correct if the frequency response
remains constant for both tests, with the same overall
level. Broadband cancellation (decreased overall level)
for the cabinet being tested indicates polarity reversal.
Polarity Between Adjacent Loudspeakers
Use the following test procedure to verify the polarity
between 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 indicates polarity reversal.
NOTE:
Checking the polarity of more than two adjacent
cabinets in one test may damage the drivers in the
cabinet with reversed polarity.
