Re: Randy chalenges speaker cable manufacturer

On Mon, 08 Oct 2007 05:30:22 +0100, Eeyore wrote:



Fred Abse wrote:

Eeyore wrote:

They are claiming that an unspecified "competitor's cable" is more
than 6 dB down at 20kHz ! Bizarrely they reckon their own cable is
over a dB down at 20kHz too !

I got to thinking about this. Audio isn't my field, but transmission
lines are. Looking at the article quoted, I noticed that they were
comparing a pair against a quad line, using loudspeakers as loads, and
comparing the voltages at the speaker terminals.

A quick and dirty Spice model of a single transmission line versus two
in parallel, both having 23ns delay (14feet at 1ns per foot corrected
for 0.6 propagation factor) into loads consisting of resistance and
inductance in series shows a pronounced difference, with the quad
rolling off at a higher frequency (pair down 3dB at 20kHz, quad down 3dB
at 37KHz , using loads of 1 ohm in series with 1 microhenry). I don't
know enough about loudspeakers to even *guess* at a realistic load
model, but it shows maybe how the published "results" were obtained.

What kind of transmission line ? What parameters did you use ?


Maybe somebody with a reasonable model for a loudspeaker could expand on
this...

The DC resistance of a typical speaker is never going to be as low as 1
ohm.

However, modelling a real world speaker cabinet is never going to please
everyone since they vary so much. I imagine they must have found some
extraordinarily difficult load to have produced the result they publish.


So, make a 4-or 6-conductor speaker cable out of a bundle of 39 cent
wire, get an A-B switch, and see if anyone can tell the differernce
if they don't already know which cable is which.

Heck, if I really thought my cables were that good, I wouldn't pooh-pooh
Randi out of hand - I'd go for the million bucks!

Cheers!
Rich


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