Audio wires can be divided into two groups:
line level signals and speaker level signals. The line level signal is
a low power signal used to transfer audio information from sources to
amplifiers. Amplifiers output speaker level signals that drive the speaker
themselves.
Line Level Signals
There are 4 common line level signals.
- Analog "line
level stereo" audio is the most common. It uses 2 wires to provide
the left and right stereo signals available on most video content such
as broadcast TV, CDs and DVDs. It uses RCA connectors or stereo jacks
and one can be converted to the other easily.
- Some DVD players
also output 5.1 multichannel sound as line level analog audio. This is
only applicable to disks that are using the SACD (Super Audio CD) or DVD
Audio formats. Regular video DVDs do not use this format. Therefore, if
your DVD player and AV surround receiver support 5.1 line level signals,
you would want to wire these ports together, but you would also want to
use one of the other signals listed here for the regular DVDs.
- Digital coax (a.k.a.,
S/PDIF on RCA where S/PDIF stands for Sony/Philips Digital InterFace),
which provides a high quality multichannel digital signal, is the preferred
interface method for distances up to 10 meters.
- Digital optical
(a.k.a., S/PDIF on TOSLink) provides a high quality multichannel digital
signal that can travel long distances over fiber optic cable.
In addition to the common line level signals
above, occasionally you will see balanced line level signals which may
use RCA phono plugs, ¼” phone jacks, or XLR plugs. Balanced line level
signals can be used for sending high quality analog audio signals long
distances, but this is pretty rare in most homes. Also in this group of
non-speaker level signals you find the HDMI and TCP/IP digital signals
that are discussed in the video section.
RCA |
Digital Coax
S/PDIF on RCA |
Digital Optical
S/PDIF on Toslink |
Speaker Level Signals
From the output of the amplifier to the input
of the speaker is the speaker level wire. This is an area of great debate,
but there are a few things most people agree on.
- The resistance
of the wire vs. the resistance (impedance) of the speaker makes a difference.
Toward this end, thicker wires have less resistance, and longer wires
have more resistance. Therefore, the longer the run from the amplifier
to the speaker, the thicker the wire you should use. Silver wire has lower
resistance than copper wire so you can use thinner silver wires, but silver
also costs more so you may end up paying more for the thinner wire. As
you go from 8 ohm speakers to 4 ohm speakers, the resistance of the wire
must be cut in half to maintain the same performance. Also, the resistance
of the speaker may vary depending on the frequency of the music being
played (i.e., the impedance is not constant over the audio frequency range).
Therefore, it is important to match the resistance of the wire to the
resistance of the speakers that will be used. Putting this all together,
you may want to try to maintain the resistance of the wire at less than
5% of the lowest resistance of the speakers over the audio frequency range.
For an 8 ohm speaker, use at least 20 gauge wire for runs of less than
20 feet and at least 16 gauge wire for runs up to 50 feet.
- For runs less
than 50 feet, some people believe that the capacitance of the wire can
degrade performance in that when it is combined with the resistance of
the wire it creates a low pass filter and limits the high frequency response.
Others say that the capacitance of even the least expensive wire is not
a factor in the audio range for relatively short distances. The former
group would recommend low capacitance wire. The latter group would tell
you that the 16 gauge power cord used to provide power to a lamp will
produce the same performance from the speakers as the low capacitance
wire.
- For runs longer
than 50 feet, most people will agree that the capacitance of the wire
can reduce the performance obtained by high quality speakers in an acoustically
ideal room. However, long wire lengths are typically associated with driving
in-wall speakers in rooms that are designed for other purposes (such as
kitchens and playrooms). For these applications, any 16 gauge wire may
be fine. If you need a better quality signal, send a balanced line level
signal or optical digital signal to the room and put the amplifier in
that room.
- People who buy
more expensive speakers are usually more willing to pay more for the speaker
wire. As the price of the speakers go up, the relative cost of the potential
improvement in performance from higher quality wire may make it worth
the cost.
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