Final Sound S100 - Manual (Page 10)

Contents Copyright 2006 Final Sound Solutions.
11. SUBWOOFER FAQ
How can I connect my subwoofer and avoid hum and noise?
Hum and noise in audio systems is caused by many interference sources . Most likely is the existence of a so-called
ground loop . If there is more than one ground connection path between two pieces of equipment, a ground loop
occurs . You can identify ground loop problems because they mostly produce a 50Hz or 60Hz hum into the system . If
the hum is 100Hz or 120Hz, without the 50/60Hz part, there are probably other sources of interference . Think about
light dimmers, heavy equipment on the same power group or strong incoming rfi/emc pollution . If hum and noise
problems are persistent, the best advice is to consult your dealer . These problems can be pretty complex in daily life .
In this FAQ, we cannot describe all the existing knowledge about ground loops in depth . We can provide you with
some basic solutions to prevent hum and noise problems .
• 100/120Hz hum can be avoided by feeding the equipment using a ‘clean’ AC line . So, don’t connect light dimmers,
refrigerators, vacuum cleaners, fluorescent lightning and other current hungry and interference inducing
equipment to the same AC-group or wall-outlet .
• Don’t put all kinds of wireless equipment, including cordless cell phones and remote controlled children’s toys in
the neighborhood of audio and video gear .
• Use shielded AC power cables to avoid incoming rfi/emc interference . Sources can be radar equipment,
transmitters for broadcast or cellular communications or your neighbor’s wireless LAN .
• Mains transformers cause an AC magnetic field around them . If you stack equipment, or if you position gear close
together, the magnetic fields can be coupled and hum may result .
• Magnetic fields can also be coupled to cables . So isolate signal cables, AC cables and cables transporting control
signals from each other . If there is a need to cross signal cables and power cables, cross with a 90-degree angle .
• Be sure that all the cables and connectors are in good shape, and that you made the connections according to
the dealer’s instructions .
• Mains voltage quality problems can cause hum and noise . Sometimes, the sine wave is distorted and the line will
contain harmonics . Please consult your dealer about using isolation transformers, mains filters and AC power
stabilizers and conditioners .
• A typical ground loop problem can occur when two interconnected pieces of equipment (FI . cd player and
amplifier) are plugged into grounded AC wall outlets at separate locations . The signal ground is connected to
earth in each of them . Try to use ‘single-point grounding’ . Connect your equipment to the same wall outlet .
• Using the subwoofer’s high-level input, can present a new league of potential hum problems . It’s known that
some amplifiers in the market come with reversed loudspeaker connections . So, red is actually ground and the
black terminal contains the ‘hot signal’ . When connecting to a subwoofer, hum may result . Try to reverse the
connections (subwoofer ‘off’ and volume to minimum) . Power the sub again and gently raise the volume . If hum
still occurs, it’s probably caused by some other phenomenon .
• Amplifiers with ‘balanced’ outputs can also be incompatible with the sub’s high-level inputs . Transformer isolation
at the amplifier’s input side may be the right solution . Please consult your dealer .
• Problems may also occur when you connect the subwoofer, using its high-level inputs, in set-ups consisting of
bi-amplified loudspeakers . Please consult your dealer .
Is it possible to use multiple subs in my stereo or home theatre set-up?
Most professionals agree that using two subwoofers in a stereo set-up will provide you with better and more
dimensional low frequency reproduction . Using more subwoofers will also be a remedy against acoustic problems
and a way to accomplish a more even bass distribution in the listening room . In a stereo-system, you can connect
each of the two subwoofers ‘high level’ to the left and right loudspeaker . Depending on your electronics, in case of
a separate pre amplifier, it’s sometimes possible to connect the subwoofer direct to the pre amplifier’s rca low level
output connectors . Use the corresponding subwoofer’s low level rca input terminals .
Using multiple subwoofers in a home theatre set-up can be a little more challenging . From the single processor’s
LFE-output, it’s simply possible to daisy chain subwoofers . It’s also possible to connect one sub to the left and one to
the right front loudspeaker, using the high level connection . Using this set up, it’s most likely to adjust your
processor’s bass management features . In case of doubt, please ask your dealer’s advice .
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