Final Sound S220 - Manual (Page 24)

FINAL SOUND SOLUTIONS S220 SUBWOOFER MANUAL vs. 1.6 -US- c FSS 2006R 24
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14. 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