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From: agn@unh.cs.cmu.edu (Andreas Nowatzyk)
Newsgroups: rec.audio,sci.physics,sci.electronics
Subject: Re: Mercury Filled Speaker Wire (really dispersion)
Message-ID: <1014@unh.cs.cmu.edu>
Date: Fri, 18-Sep-87 11:25:21 EDT
Article-I.D.: unh.1014
Posted: Fri Sep 18 11:25:21 1987
Date-Received: Sun, 20-Sep-87 03:09:39 EDT
References: <3816@watdcsu.waterloo.edu> <578@uthub.toronto.edu>
Organization: Carnegie-Mellon University, CS/RI
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Xref: mnetor rec.audio:3322 sci.physics:2206 sci.electronics:1355

The phenomenon of dispersion in cables has been brought up to explain alleged
differences in speaker cables. Let's see: dispersion is a frequency dependent
change in the cable delay that is observed in a transmission line. The delay
of a transmission line is roughly:

   Tpd = 1.017 * sqrt (0.475 * e + 0.67)        [ns/ft]

where "e" is the relative dielectric constant of the insulator, which in turn
is dependent on the frequency. Let's assume a really bad insulator (you won't
be able to find one like that) that has e(dc)=5 and e(20Khz)=2.5.
So this insulator behaves like PVC at DC and like Teflon at 20Khz. Assuming
30 ft cable legnth, we get: Tpd(DC) = 53 ns,  Tpd(20Khz) = 42 ns.

That cable must sound awfull: the high frequencies arrive 11ns earlier!! :-)
This is a phase error of 0.08 degrees.

Audiophile: Someone who can hear the color of the front panel.

-- 
   --  Andreas Nowatzyk  (DC5ZV)

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