Meyer Sound MSL-6 - Manual (Page 10)

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.
Driver Troubleshooting with TPL
The TPL LEDs can indicate serious driver problems, if
interpreted correctly. If one MSL-6 in a system exhibits
substantially more TPL activity than others receiving
the same audio signal, then one of the drivers corre-
sponding to the excessively active LED may have a short
circuit. This is a potentially dangerous condition for the
electronics; shut the MSL-6 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 MSL-6s 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.
Removal, Inspection, and Replacement
To determine whether a low or high frequency 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) or the High Driver Inspection
and Evaluation Procedure for Self-Powered Series
Products (part # 17.010.120.02). These documents are
accurate for inspection and verification but have yet to
be updated for the different driver removal procedure
for the MSL-6.
The MSL-6 has two rear hatch covers that must be re-
moved to access the high and low drivers. Remove the
screws for either hatch with a Phillips screwdriver. The
hatch is sealed with a rubber gasket so it must be pulled
off with moderate force.
Use a 7 /
16
” open-end wrench to remove the nuts that
secure the high driver to the horn. Hold the driver as the
final nut is removed to prevent it from falling. Twist the
driver sideways and up/down to remove it from the
back of the cabinet.
Use a 3 /
16
” hex wrench to remove the nuts that mount
the low driver. Support the driver as the last nut is
removed to prevent it from falling. Twist the driver
sideways and up/down to remove it from the back of
the cabinet.
Verifying Polarity
Incorrect driver polarity impairs system performance
and may damage the drivers. All Meyer Sound loud-
speakers are shipped with the drivers in correct align-
ment. However, if the driver or circuit wiring has been
removed or disassembled in any loudspeaker in a system
for any reason, check the polarity between adjacent
loudspeakers and between drivers in the same cabinet.
We recommend that SIM System II be used to check
polarity but a real-time frequency analyzer with one-
third octave resolution is adequate.
!
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 be-
tween high frequency horn drivers:
1. Place a monitoring microphone 5 ft from the grill
frame, 8.5” below the top of the speaker, at the mid-
point of the center horn (center-line of cabinet).
2. Connect a signal source to the loudspeaker and
note the frequency response.
The polarity of the high drivers is correct if the fre-
quency response is
±
3 dB 1 – 4 kHz. Polarity reversal for
the center or outer horns is indicated by 12 – 15 dB
cancellation in the same region. Check the wiring to the
high frequency drivers and to the MP-4 and correct the
problem.
Use the following test to verify polarity between low
frequency drivers:
1. Place a monitoring microphone 5 ft from the grill
frame, 28” below the top of the cabinet, at the mid-
point between low drivers (center-line of cabinet).
2. Connect a signal source to the loudspeaker and
note the frequency response.
The polarity of the low drivers is correct if the frequency
response is
±
3 dB 125 – 500 Hz. Polarity reversal for one
of the low drivers is indicated by 12 – 15 dB cancellation
in the same region. Check the wiring to the low drivers
and to the MP-4 and correct the problem.