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From: ornitz@kodak.UUCP (barry ornitz)
Newsgroups: rec.audio,sci.physics,sci.electronics
Subject: Re: Mercury Filled Speaker Wire
Message-ID: <958@kodak.UUCP>
Date: Wed, 23-Sep-87 18:33:36 EDT
Article-I.D.: kodak.958
Posted: Wed Sep 23 18:33:36 1987
Date-Received: Sat, 26-Sep-87 07:56:28 EDT
References: <1549@culdev1.UUCP> <1130@hounx.UUCP>
Reply-To: ornitz@kodak.UUCP (barry ornitz)
Organization: Eastman Kodak Co, Rochester, NY
Lines: 45
Keywords: wavelength, velocity factor
Summary: Wavelength in wire is electrical wavelength.
Xref: mnetor rec.audio:3398 sci.physics:2261 sci.electronics:1410

In article <1130@hounx.UUCP> jong@hounx.UUCP (J.LEE) writes:
>In article <1549@culdev1.UUCP>, drw@culdev1.UUCP (Dale Worley) writes:
>> As long as we're debunking things, note that the "skin effect" (if
>> it's the skin effect I know and love) involves a "penetration depth"
>> measured in fractions of a wavelength.  Since the wavelength at 20kHz
>> is ... hmmm ... 5 kilometers, it doesn't seem too significant.
>> 
>
>The wave length of 20 K Hz tone is 5 kilometers???
>Nah.  The velocity of sound is about 300 m/s at room temperature.
>This makes the wave length of 20 KHz sinusoid 0.015m (=300/20k)
>or 1.5 cm (~0.6 in). Granted, this is still much larger than
>most audio conductor diameter. As to whether this causes audible
>phase dispersion or not, I am still not sure.  I am still
>experimenting... .
>
>Regards.    J Lee, Bell Labs, Holmdel, NJ.

Just what goes on here?  Certainly the readers of wreck.audio have more
sense than this.  We are talking electrical wavelength here, not acoustical
wavelength.  The electrical wavelength is the speed of light divided by the
frequency multiplied by the velocity factor of the cable.  The velocity
factor is the reciprocal of the square root of the dielectric constant of
the wire insulation.  For polyethylene, as an example, the velocity factor is
about 0.66 and the wavelength at 20 KHz is about 32,500 feet.

Just what does acoustical wavelength have to do with speaker wire?  Maybe
since the resistance of the mercury filled wire is mechanical stress
dependent, acoustic waves impinging on the cable could cause resistance
changes leading to a form of acoustic (and electrical) cross modulation
which is certainly nonlinear and hence a no-no to audio phreaks.  Besides
the sonic velocity of a material is density related; it is much higher in
copper than in air.

BTW - I won't be sorry to see the Commander disappear but I will miss Pierce.

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|  ___  ________  |
| |  / /        | |  Dr. Barry L. Ornitz   UUCP:...!rochester!kodak!ornitz
| | / /         | |  Eastman Kodak Company
| |< < K O D A K| |  Eastman Chemicals Division Research Laboratories
| | \ \         | |  P. O. Box 1972
| |__\ \________| |  Kingsport, TN  37662       615/229-4904
|                 |
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