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.
In summary, there are no perfect cables. The best way to
approximate the ideal would be to keep loudspeaker leads as
short as is practical.
8
To Next Page
Loading...
Need help?
General
