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THX subwoofers page 15
e. If the red LED is still lit, set the "BASS LEVEL" switch to the "VARIABLE" position. Turn the
"BASS LEVEL" control to "MIN". Plug a standard RCA cable into the "LEFT/MONO" "FROM
PREAMP" jacks. Lightly touch the plug at the free end of the cable. Then turn the "BASS LEVEL"
control clockwise. If you hear a buzz or hum from the subwoofer when you touch the cable, the
subwoofer is working. Look elsewhere in your system for the problem. If you hear no output, contact
your dealer or M&K for service.
f. Make sure all cables are OK. Double check all connections and replace any defective cables.
2. If the midbass range (the area of transition between Subwoofer and Satellite or L/C/R
speakers) sounds weak:
See Section 7, SATELLITE/SUBWOOFER PHASING TEST, on page 12. Reverse the position of
the "PHASE" switch on the back of the subwoofer. The position that gives the most bass is correct.
3. If you hear a thump through the subwoofer every time you turn the rest of your audio
system on (and your subwoofer is plugged in all the time):
Either the preamp, amp, receiver, or surround sound processor is generating the thump, and the
subwoofer is reproducing it. Contact your dealer or the manufacturer of the other component.
4. If you hear a persistent hum or buzz through the subwoofer:
Because the subwoofer easily reproduces 60 Hz signals (the frequency of hum), 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. Placing wires and cables
close to AC lines often results in hum. If necessary, reroute your cables.
To identify a source of hum, remove all input cables to the subwoofer, but leave it plugged into the
AC outlet. Set the "BASS LEVEL" switch to the "VARIABLE" position. Carefully turn the "BASS
LEVEL" control up towards the "MAX" position. If you hear hum from the subwoofer, it is the source
of hum. If you hear no hum or much less hum, the problem is in another component or a ground loop.
For ground loop problems, when the subwoofer is plugged into a separate AC outlet, try plugging
it into the same outlet as your amplifier or receiver. If that doesn't work, reverse the polarity of its AC
plug. If you cannot solve the problem, call M&K or your dealer.
5. If you hear an unusual sound from the subwoofer when no signal or music is playing:
Try removing the input cables as described in Step 4 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.
6. If the subwoofer will not play loud enough, AND it is connected to the SUBWOOFER
OUTPUT jack on a non-THX surround sound processor:
Make sure that the "BASS LEVEL" toggle switch is set to "VARIABLE." Set the "BASS LEVEL"
control to the "MAX" position. If you get bass output, but it is not enough, then the processor's output
level is too low.
Some surround processors/receivers/amps have very low output levels from their SUBWOOFER
OUTPUT jacks. If you do not have enough gain when using the SUBWOOFER OUTPUT jacks on a
non-THX processor, use the processor's PREAMP OUTPUT jacks. See Figures 5 and 6 (page 10).
IF YOU NEED TO REPLACE THE EXTERNAL FUSE:
Unplug the subwoofer from the wall AC socket. Remove the fuse cap. Look carefully at the wire
filament inside the glass. If it is broken, replace the fuse ONLY with one identical in size and value.
Using a larger fuse will void your warranty AND MAY CREATE A FIRE HAZARD. Plug the subwoofer
back in. If it does not work, unplug it immediately. Contact M&K or your dealer for service.