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Propeller Head Plaza Technical and scientific discussion of amps, cables and other topics. |
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Original Message
RE: All of that is pretty cool, but
Posted by tomservo on June 22, 2010 at 08:33:01:
"Was the speaker cable test using the box conducted with the speakers on the tower with 100' of run for each cable?"
No, for the listening tests, the cables were what the attendees brought and varied from 10 feet to about 30 feet (10 meters i would guess)in length.
For the measurement set up, each cable type was measured open and close circuit to determine the series L, R and parallel C, ALL of these properties are directly proportional to the length so one the values 'per foot" are determined, then the effect of any length out to about 1/8 wavelength can be calculated. At 20KHz, 1/8 wl is still well over a mile so there is no transmission line effect to be concerned with in audio cables normally..
Interestingly, one cable type was significantly worse than lamp cord, that was the generic round hardware store extension cord. It has much more space between conductors and so had by far the highest inductance per foot.
That series inductance can only exist when there is uncoupled flux between the two conductors (which carry equal but opposing currents), the self shielding of the coax apraoach or the weaving (and extension of twisted pair) greatly reduces the un-coupled flux which is why these types have low series L.
Best,
Tom