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Cable studies.

Posted by Clayton Oxendine on April 20, 1999 at 15:14:07

I got this off of a list I belong to, amd have not seen anything like it as to cable studies. Sounds interesting. Did not post the guys name who posted it.

Clayton

> Warning, long post (Summary of a study)
>
> About once a year this topic comes up and somesone makes an uninformed
> statement similar to the one below. I usually make one post pointin to an
> article appeared in the Winter Audio Ideas Guide (an objectivist
> publication) that gave the results of
> an extensive test of speaker cables that showed they do measure differently
> and that difference is audible. In the past I've dropped it there and assumed
> those interested would search out the reference. Seems the reference drops
> into
> an objectivist black hole so here is a summary.
>
> The article and study was done by James H. Haward. "Recently retired from
> Bell Canada Special Services Engineering and Operations Groups, Jim Hayward
> is a Ryerson
> Electronics Technology graduate whose professional specialty has been data
> communications and radio systems. He is also a pianist and longtime
> audiophile, and currently teaches at Radio College of Canada in Toronto."
>
> Paraphrasing:
>
> The laws of physics are the same regardles of which end of the power amp
> you observe. That said, there is one parameter that causes a profound
> difference in performance. It is the impedance interface.
>
> He procedes to outline aspect of cables, Zs,R and L. and follows with
>
> "a recent study of nyquist plots of the complex impedance curves of 21
> speaker systems wasn't good news for those audiophiles who believe the
> world would be a better place if all the audiophiles invested in
> transmissin lines with a characteristic impedance of 8 ohms. ... the
> minimum impedance being one ohm and the maximum 28 ohms. Phase deviations
> abounded between maximums of =56 and -67.5 degrees.
> As if that wasn't bad enough, a number of scientific reports indicate that
> certain dynamic signals...applied to speaker systems can cause a current
> flow that is up to two and a half times greater than that predicted from
> the speaker's minimum impedance."
>
> The power amp must be capable of delivering very high current and have an
> output
> impedance of nearly zero. A power amp must behave as much as possible like a
> perfect voltage source. In other words , its output voltage must not be
> influanced by changes in load impedance. ... Lets take an actual cable
> parameter and see how
> its impact changes withy the magnitude of the source and load impedance. 500pF
> is a typical value for parallel capacitance of 3 meter length of ... speaker
> cable. As capacitance reactance is lowest at high frequencies, lets analyze
> its
> impact at 20kHz where its nasty shunting behavior will be most detrimental.
> It's capacitive reactance is about 16 kohms at 20 kHz and this is in parallel
> with the load. If the source is a passive preamp with an output impedance
> of 16
> kohms also, the frequency response will be down 3dB at 20kHz. Also, a high
> impedance
> preamp must drive a very high input impedance power amp to avois excessive
> loading.
> so if in our example, the input impedance of the power amp was 250 kohms,
> there would be over fifteen times more current flowing through the cables
> capacitive reactance to
> ground than threouh the input of the power amp at 20 kHz.
>
> Discussion of features necessary for high performance speaker cables omittd
> for brevity.
>
> The following speaker cables were measured and studied
> Prism Time-Compensated
> Nordst Flatline
> Kimber 8TC
> Kimber 4TC
> Cardas Quadlink 5C
> van den Hul The Revelation
> van den hull Hybrid
> Amphenol RG8/U
> lamp cord (16 AWG)
>
> Impedance vs. Frequcecy (mohms)
> Below 2kHz all cables were bunched together below 50. Lamp cord ran about
> twice as much. The cables radically diverge above 2kHz - at 20 kHz they
> vary from 130 to 780. Flat impedance is better.
>
> Conclusions
>
> Risetime Tells Tells ... The cable with the shortest risetime is the one with
> the largerst bandwidth. It is also an excellent indicator ofuniform
> frequency and phase behavior within the audio spectrum. Low inductance
> cables have the flattest
> frequency response and shortest rise time. Cables with very low resistance are
> only contenders if they have low inductance also.
>
> Minimise power loss by using more cables. Bi-wire or bi amp. Not only does it
> reduce current in each cable but it reduces intermodulation distortion as
> well.
> (My aside-bi-wire with cheaper stiff for low/mids and quality stuff for hf.)
>
> Bi amping is expensive but the results are stunning.
>
> What speaker cables came oyt on top?
> 1. Kimber 8TC by a long shot
> 2. Kimber 4TC by a long shot.
>
> If anyone wants to discuss this, leave me out. This is presented for
> information
> only, not interested in debates. I someone can post information from extensive
> studies that directly contradict this I would be interested in seeing such.

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