MK Sound VX-850 Operation Manual page 11

POWERED SUBWOOFER
5. If the red LED is lit, try this test: Turn the "BASS LEVEL" control to "MIN". Plug a standard
RCA cable into the "FROM PREAMP" jacks. Lightly touch the plug at the free end of the cable,
while slowly turning the "BASS LEVEL" control clockwise.
subwoofer when you touch the cable, the subwoofer is functioning. Look elsewhere in your
system for the problem. If you hear no noise, contact your dealer or M&K.
6. Make sure that the input cables are OK. Double check your connections. If necessary, replace
any defective cables or speaker wires.
B. If, after operating the woofer at high volume levels for a long time, the woofer cuts out or becomes
intermittent:
Your subwoofer has a protection circuit that protects it from overheating. After hours of continuous
operation at extremely high volume levels, this circuit may cut off the power to the subwoofer. When
it activates, the sound may switch in and out rapidly, with a fluttering sound. If this happens, unplug the
unit and let it sit for at least half an hour. After that time, plug it back in. It should operate normally.
If you find this happens frequently, contact the factory for advice.
C. If you are using the "FROM AMPLIFIER" terminals, and the subwoofer has very little output:
Make sure that the input cables are in phase. Reverse the (+) and the ( — ) connections for ONE
CHANNEL ONLY at the "FROM AMPLIFIER" terminals. If the problem remains, put the cables back as
they were. Then perform the test in Step 4.
D. If the midbass range (the area of transition between Subwoofer and Satellite speakers) sounds weak:
Refer to Section 6, Phasing Test, on page 9. Reverse the (+) and ( — ) connections at the back of
BOTH Satellite speakers, OR switch the "PHASE" switch from (+) to ( — ) or vice versa. The wiring
configuration that gives the most bass is correct.
E. If you are using the "FROM PREAMP" input terminals, and you hear a thump through the Subwoofer
every time you turn the system on:
F. If you hear a persistent hum or buzz through the subwoofer:
Because the subwoofer reproduces the 60 Hz hum frequency, it is often blamed for causing hum that
originates elsewhere in the system. Always avoid running all speaker wires and RCA interconnect
cables near to AC cords and component power supplies. Wires and cables running close to AC lines
are a common source of hum. If necessary, reroute your cables.
To identify the source of hum, remove all input cables to the subwoofer, but leave it plugged into the
AC outlet. Carefully turn the "BASS LEVEL" control up towards the "MAX" position. If you hear hum
coming from the subwoofer's speaker driver, the subwoofer is the source of the hum. If you hear no
hum or less hum, the problem is probably coming from another component.
Hum can also be caused by AC ground loops. If the subwoofer is plugged into a separate AC outlet,
try plugging it into the same outlet used for your amplifier or receiver, or reverse the polarity of its AC
plug. If these suggestions do not solve your problems, contact your dealer or M&K.
G. If there is an unusual sound coming from the subwoofer with no music playing:
Try removing the input cables as described in Step 5 above. If the noise disappears, it is coming from
another component. If it does not go away, contact your M&K dealer or the factory.
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If you hear noise from the