Andrew Marshall is an audio writer/reviewer from Toronto, Ontario, Canada.
He founded AIG (Audio Ideas Guide) in the seventies; I was a subscriber for several years
? http://www.audio-ideas.com/about-aig/
I still have the mags, and few of them have articles on cables; speaker cables and interconnects...analog and digital.
But the best articles was from a guy that used to work for Bell Labs.
I would have to take pics directly from my audio mags and post them here.
It amazes me that today we don't have access to the best articles online.
Many audio mags subsist from online donations and the selling of older audio mags...if still avail.
I can name few mags like this...but you must know some of them.
Knowledge isn't free.
Give me some time to see what I can do, in relocating my mags, and if permissible to reprint those articles here.
The name of the ex-Bell Labs guy is Jim Hayward; you might have heard of him.
• Making the Connection , Part Deux: A closer look at the role of
speaker cables. Jim Hayward offers the sequel, tests a variety of
different cables, and a looks at what matters most.
There is also the first part of course. And those two articles...you cannot have more scientific than that.
Google him with Making the Connection...
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•
http://bryston.com/PDF/newsletters/Bryston_Newsletter_V5_2.pdf
•
http://www.audioasylum.com/cgi/t.mpl?f=general&m=4087
>The article and study was done by Jim H. Hayward. "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 regardless 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 proceeds 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
>transmission 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
>influenced by changes in load impedance. ... Lets take an actual cable
>parameter and see how
>its impact changes with 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 through the input of the power amp at 20 kHz.
>
>Discussion of features necessary for high performance speaker cables omitted
>for brevity.
>
>The following speaker cables were measured and studied
> Prism Time-Compensated
> Nordost Flatline
> Kimber 8TC
> Kimber 4TC
> Cardas Quadlink 5C
> van den Hul The Revelation
> van den hul 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 largest bandwidth. It is also an excellent indicator of uniform
>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.
>
>Minimize 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 on top?
> 1. Kimber 8TC by a long shot
> 2. Kimber 4TC by a long shot."
____________
This is a much longer article (just this one alone, because there are two of them, perhaps 16 pages);
very technical and scientific and based on solid electrical facts.