Phil Allison wrote:

"Jim Lesurf Criminal Audiophool Facillitator "

I've just put up a new webpage that provides some measurements on the
properties of a variety of loudspeaker cables. The page is at

http://www.audiomisc.co.uk/HFN/Cables3/TakeTheLead.html

It is an expanded version of the article published in 'Hi Fi News' a few
months ago.

** Dear UKRA readers,

the religious among us can take some comfort from the fact that

*SATAN* is currently preparing a special blast furnace in HELL

ready to take the putrid soul of one " Jim Leserf " any time soon.

SATAN is very proud of this particular, asinine pommy ****head for
spreading chaos and confusion among the masses.

So he deserves a special reward.

Burn you ****ing *******, burn.

.... Phil

You have my total support.

Graham


--
due to the hugely increased level of spam please make the obvious adjustment
to my email address

John Phillips wrote:

On 2009-08-07, Don Pearce wrote:
On Fri, 07 Aug 2009 09:10:40 +0100, Jim Lesurf
wrote:

Hi,

I've just put up a new webpage that provides some measurements on the
properties of a variety of loudspeaker cables. The page is at

http://www.audiomisc.co.uk/HFN/Cables3/TakeTheLead.html

It is an expanded version of the article published in 'Hi Fi News' a few
months ago.

No conclusions section there, but maybe as follows?

1. If you open circuit the cable at the loudspeaker end, it is better
if the cable is somewhat lossy, as this will prevent the quarter wave
Mod Z dropping to too low (potentially damaging) a value.

Alternatively, perhaps, that a well-designed amplifier will have about
2 uH of good quality inductance in series with its output to avoid such
a case becoming damaging?

Funny, that's very similar to the value I use. And it'll have a series R-C to
ground to stabilise the load the amp 'sees'. This technique has been known for
many decades. It is even used in long line-level drivers.

Graham


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to my email address

Jim Lesurf wrote:

In general, cable losses will reduce the amplitude in the presented
impdance changes with frequency in the RF region.

How good are your ears at 1MHz ?

Graham

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On Fri, 07 Aug 2009 17:31:43 +0100, Eeyore wrote:

Jim Lesurf wrote:

Hi,

I've just put up a new webpage that provides some measurements on the
properties of a variety of loudspeaker cables. The page is at

http://www.audiomisc.co.uk/HFN/Cables3/TakeTheLead.html

It is an expanded version of the article published in 'Hi Fi News' a
few months ago.

What IDIOT thinks the reactance at 30 MEGAHERTZ has any influence on the
listening experience.

And since when ( Fig 1 for example ) do you run a cable open or shorted
as a valid test ?

WHAT A COMPLETE HEAP OF MINDLESS JUNK !

You should be ashamed of yourself and run some REAL models.



I'm unsure about drawing any conclusions from graphs that start at 5x the
accepted maximum audible frequency. I hope Jim has included tests on VHF
coax as speaker leads too - it makes as much sense to me... ;-)

*If* your amp has much output above 100kHz then it is faulty and needs
looking at - seriously. It isn't allowed to be a radio transmitter by law
and 148kHz upwards interferes with the LW band!

:-)



--
Mick (Working in a M$-free zone!)
Web: http://www.nascom.info
Filtering everything posted from googlegroups to kill spam.

Jim Lesurf wrote:
Hi,

I've just put up a new webpage that provides some measurements on the
properties of a variety of loudspeaker cables. The page is at

http://www.audiomisc.co.uk/HFN/Cables3/TakeTheLead.html

It is an expanded version of the article published in 'Hi Fi News' a few
months ago.

Slainte,

Jim


FWIW it means very little to me. You seem to assume a correlation
between frequency, resistance and sound. Perhaps a paragraph or two on
what you might expect any measured result in the context of your
measurments to mean?

Rob

On Fri, 07 Aug 2009 17:31:43 +0100, Eeyore
wrote:



Jim Lesurf wrote:

Hi,

I've just put up a new webpage that provides some measurements on the
properties of a variety of loudspeaker cables. The page is at

http://www.audiomisc.co.uk/HFN/Cables3/TakeTheLead.html

It is an expanded version of the article published in 'Hi Fi News' a few
months ago.

What IDIOT thinks the reactance at 30 MEGAHERTZ has any influence on the
listening experience.

And since when ( Fig 1 for example ) do you run a cable open or shorted as a
valid test ?

WHAT A COMPLETE HEAP OF MINDLESS JUNK !

You should be ashamed of yourself and run some REAL models.

Graham

Ever heard the term "Unconditionally stable" in reference to an
amplifier? Yes, I thought you had. What that means is that it will
operate without oscillation into any combination of reactive and
resistive load (over the entire Smith chart). The reason why Naim
amplifiers don't is that they failed to consider exactly this problem
in their design. If they had just used Figure 1 (which you deride)
they might have made an acceptable product.

In my years of design I discovered something important. It doesn't
matter what is the maximum frequency you intend to put through
something. Your design must encompass the maximum frequency at which
the active devices can produce gain (something like Ft). It is all too
easy to end up with an audio amplifier which is so marginally stable
at 30MHz that it can oscillate into some loads. When that happens,
yes, there will be sonic consequences.

So, Graham, have a bit of a rethink, I suggest.

d

In message , mick
writes
On Fri, 07 Aug 2009 17:31:43 +0100, Eeyore wrote:

Jim Lesurf wrote:

Hi,

I've just put up a new webpage that provides some measurements on the
properties of a variety of loudspeaker cables. The page is at

http://www.audiomisc.co.uk/HFN/Cables3/TakeTheLead.html

It is an expanded version of the article published in 'Hi Fi News' a
few months ago.

What IDIOT thinks the reactance at 30 MEGAHERTZ has any influence on the
listening experience.

And since when ( Fig 1 for example ) do you run a cable open or shorted
as a valid test ?

WHAT A COMPLETE HEAP OF MINDLESS JUNK !

You should be ashamed of yourself and run some REAL models.



I'm unsure about drawing any conclusions from graphs that start at 5x the
accepted maximum audible frequency. I hope Jim has included tests on VHF
coax as speaker leads too - it makes as much sense to me... ;-)

*If* your amp has much output above 100kHz then it is faulty and needs
looking at - seriously. It isn't allowed to be a radio transmitter by law
and 148kHz upwards interferes with the LW band!

:-)

An audio amplifier with a frequency response well into the RF region
will not, itself, transmit RF signals (apart from a little low-level
wideband noise).

Of course, it will be a different matter if the effects of the load
impedance (seen by the amplifier) were to cause instability, and cause
the amplifier to oscillate. Such oscillations could occur in the RF
region and, even if the oscillation itself was 'sub-RF', there could be
substantial levels of RF harmonics.
--
Ian

In article , Eeyore
wrote:


Jim Lesurf wrote:

Hi,

I've just put up a new webpage that provides some measurements on the
properties of a variety of loudspeaker cables. The page is at

http://www.audiomisc.co.uk/HFN/Cables3/TakeTheLead.html

It is an expanded version of the article published in 'Hi Fi News' a
few months ago.

What IDIOT thinks the reactance at 30 MEGAHERTZ has any influence on the
listening experience.

Perhaps those who have observed more than one audio power amp oscillating
at RF as a result of the loading presented to it, and the amp not being
unconditionally stable. (Yes, including commercial designs.) Plus perhaps
having observed changes in the audio-band distortion behaviour as a result
of loading above the audible range.

And since when ( Fig 1 for example ) do you run a cable open or shorted
as a valid test ?

Surprised you don't understand that as I understand you are an engineer,
although I guess you may be unfamiliar with the methods that RF and
microwave engineering might employ for such things.

The measurements into an open and a short allow you to determine the
cable's complex impedance and propagation properties as a function of
frequency. They also give you some indication of the size of any impedance
swings the amp will experience into unpredicted loads. In essence at each
frequency the two complex values for the presented impedance allow you to
work out the required values for the cable.

WHAT A COMPLETE HEAP OF MINDLESS JUNK !

You should be ashamed of yourself and run some REAL models.

Alternatively, you could be embarassed by attacking in a way that shows
that your objections are based on not pausing first to understand the
reasons for the measurements. :-)

Slainte,

Jim

--
Please use the address on the audiomisc page if you wish to email me.
Electronics http://www.st-and.ac.uk/~www_pa/Scot...o/electron.htm
Armstrong Audio http://www.audiomisc.co.uk/Armstrong/armstrong.html
Audio Misc http://www.audiomisc.co.uk/index.html

In article , Eeyore
wrote:


John Phillips wrote:


Alternatively, perhaps, that a well-designed amplifier will have about
2 uH of good quality inductance in series with its output to avoid
such a case becoming damaging?

Funny, that's very similar to the value I use. And it'll have a series
R-C to ground to stabilise the load the amp 'sees'. This technique has
been known for many decades.

Yes. I have always done the same. However some designers don't, and it is
possible for people to choose incorrect values, or use an inductor whose
self-resonance is too low in frequency.

Slainte,

Jim

--
Please use the address on the audiomisc page if you wish to email me.
Electronics http://www.st-and.ac.uk/~www_pa/Scot...o/electron.htm
Armstrong Audio http://www.audiomisc.co.uk/Armstrong/armstrong.html
Audio Misc http://www.audiomisc.co.uk/index.html

In article , Eeyore
wrote:


Jim Lesurf wrote:

In general, cable losses will reduce the amplitude in the presented
impdance changes with frequency in the RF region.

How good are your ears at 1MHz ?

Afraid I can't hear 1MHz. But I have heard - and measured - a change in
amplifier performance in cases where the amp has been producing bursts of
oscillations at such frequencies with loads it did not like at RF.

As before, I am quite surprised that someone who I thought had designed and
tested amp may not have encountered this.

Slainte,

Jim

--
Please use the address on the audiomisc page if you wish to email me.
Electronics http://www.st-and.ac.uk/~www_pa/Scot...o/electron.htm
Armstrong Audio http://www.audiomisc.co.uk/Armstrong/armstrong.html
Audio Misc http://www.audiomisc.co.uk/index.html