Legacy Skyline Owner's Manual - Hook-Up Cables
Hook-up Cables
The ideal conductor would have negligible resistance, inductance
and capacitance. The table below shows how a few actual speaker
cables measure up.
Cable
Ωs/ft
pF/ft
µH/ft
12 ga.
0.0033
24
0.21
14 ga.
0.0048
17
0.13
16 ga.
0.0079
16
0.18
18 ga.
0.0128
28
0.21
Capacitance is considered insignificant in each cable because its
effect is well out of the audio bandwidth; inductance can be
decreased (at the expense of increased capacitance) by keeping the
conductor pair closely spaced.
How long would a cable have to be before inductance effects
would impinge on the audio spectrum? Approximately 300 feet of 12
gauge would be required to establish a corner frequency of 20 kHz
with an 8 ohm loudspeaker. As you see, inductance is not a problem
for most of us.
What about phase shift due to frequency dependent travel times
down the speaker cable? Measurements show that 100 Hz waves will
be delayed about 20 billionths of a second behind 10 kHz waves
when traveling to the end of a 10 foot speaker cable. Since the cilia
of the ear requires 25,000 times longer than this just to transmit
phase information, phase shifting is obviously not the primary
concern when considering speaker cables.
What about resistance? Finally we are getting somewhere.
Resistance is the controlling factor of the amplifier/loudspeaker
interface.
Excessive resistance can cause major shifts of speaker crossover
frequencies. The lower the impedance of the loudspeaker, the greater
the effects of series resistance. A run of 20 feet of 18 gauge can cause
up to 10% deviations of crossover center frequencies. That same 20
feet can undamp your damping factor and reduce your systems’
output by one-half decibel.
The best way to approximate the ideal would be to keep
loudspeaker leads as short as is practical. However, for rear room
installation, cable runs exceeding 50 feet are not unusual. Using an in-
wall approved cable of 12 guage is recommended.
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