Owner’
s Manual
15
Owner’s Manual
Appendix A: Service Information
Poor bass performance
• Check the polarity of the connections between the
mixer and the subwoofers. You may have your
positive and negative connections reversed at one
end of one cable, causing one subwoofer to be
out-of-phase with the other.
• Poor bass performance may be the result of bad
AC power. See the section titled ‘AC Power’ on
the previous page for further details.
Poor sound
• Is it loud and distorted? Make sure that you’re not
overdriving a stage in the signal chain. Verify that
all level controls are set properly.
• Is the input connector plugged completely into
the jack? Be sure all connections are secure.
Noise
• Make sure all connections to the active
subwoofers are good and sound.
• Make sure none of the signal cables are routed
near AC cables, power transformers, or other
EMI-inducing devices.
• Is there a light dimmer or other SCR-based device
on the same AC circuit as the DLM12S? Use an
AC line filter or plug the subwoofer into a
different AC circuit.
Hum
• Try disconnecting the cable connected to the
input jack. If the noise disappears, it could be
a “ground loop,” rather than a problem with the
DLM12S subwoofer. Try some of the following
troubleshooting ideas:
• Use balanced connections throughout your system
for the best noise rejection.
• Whenever possible, plug all the audio equipment’s
line cords into outlets which share a common
ground. The distance between the outlets and the
common ground should be as short as possible.
If you think your Mackie product has a problem,
please check out the following troubleshooting tips and
do your best to confirm the problem. Visit the Support
section of our website (www.mackie.com/support)
where you will find lots of useful information such as
FAQs and other documentation. You may find the answer
to the problem without having to send your Mackie
product away.
Troubleshooting
No power
• Our favorite question: Is it plugged in? Make sure
the AC outlet is live [check with a tester or lamp].
• Our next favorite question: Is the power switch
on? If not, try turning it on.
• Make sure the line cord is securely seated in the
line cord socket and plugged all the way into the
AC outlet.
• Is the power LED on the front panel glowing
green? If not, make sure the AC outlet is live.
If so, refer to “No sound” below.
• The internal AC line fuse may be blown. This is
not a user serviceable part. If you suspect the
AC line fuse is blown, please see the "Repair"
section next.
No sound
• Is the input level control for the input source
turned all the way down? Verify that all the volume
controls in the system are properly adjusted.
Look at the level meter to ensure that the mixer
is receiving a signal.
• Is the signal source working? Make sure the
connecting cables are in good repair and securely
connected at both ends. Make sure the output
volume (gain) control on the mixing console is
turned up sufficiently to drive the inputs of the
speaker.
• Make sure the mixer does not have a mute on or a
processor loop engaged. If you find something like
this, make sure the volume/gain is turned down
before disengaging the offending switch.
• Has it shut down? Make sure there is at least
six inches of free space behind each DLM
subwoofer.
