kyser wrote:
I'm embroiled in a discussion on aus.hifi with a poster who recommends the
use of RG58C/U as speaker cable (with alleged sonic improvements over
standard figure-8 type flex).
Wouldn't the combined inductance/capacitance of this stuff constitute an LC
filter causing signal attenuation or, worse, amp output stage instability
over anything but a short run?
Patrick Turner? Anyone?
TIA
The RG58's do have a rather high capacitance, on the order of 30 pF per
foot (~100 pF per meter). So for an extreme case let's take, say, a 100
meter run (over 300 feet). The capacitance would be .01 uF. On an 8 ohm
system, assuming a 0-ohm amplifier output impedance, that would put the
3 dB corner at about 2 megahertz. *Well* above the human range of
hearing. So from a capacitive POV, not to worry.
Inductance and lumped inductance/capacitance effects don't significantly
come into play at audio frequencies either. Again, not to worry.
The only problem I can see is ordinary, every-day resistance. The center
conductor in RG58 is quite small, perhaps only about 20-gauge. Let's
see... (I love my Google) - 10.4 ohms per 1000 feet. So to continue the
same example, you'd be losing about 1/3 of your output power in the
stupid speaker wire! Bad idea.
But you've just given me an idea. If audiophools are going for el-cheapo
coax, they'll just love LMR400! This stuff is big and ugly (about 1/2"
in diameter), stiff as a board and impossible to work with, has an
aluminum foil *and* a braided tinned copper shield, foam dielectric (low
capacitance), and very thick single-strand center conductor. Try running
*that* crap through a building and up a tower in the dead of winter
sometime!
I can get it for about a buck a foot. If I sell it for $5 a foot, that
would be suitable revenge both on LMR400 and on the audiophools that buy
it! ;-)
Cheers,
Fred
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