[Ian Iveson]

Posted by Jim Lesurf on uk.rec.audio:

"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."

Wadya think?

Ian

[Bob Eld]

"Ian Iveson" wrote in message
...
Posted by Jim Lesurf on uk.rec.audio:

"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."

Wadya think?

Ian

Pure unadulterated nonsense of zero meaning or consequence. Maybe you didn't
realize it but audio frequencies are ALL below 100kHz. Your measurements are
in the megahertz range. What possible effect do they convey to sound
quality? Be imaginative in your explanation we're all ears!

[Eeyore[_3_]]

Bob Eld wrote:

"Ian Iveson" wrote

Posted by Jim Lesurf on uk.rec.audio:

"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."

Wadya think?

Pure unadulterated nonsense of zero meaning or consequence. Maybe you didn't
realize it but audio frequencies are ALL below 100kHz. Your measurements are
in the megahertz range. What possible effect do they convey to sound
quality? Be imaginative in your explanation we're all ears!

Maybe you'd like to join my crusade about Jim Lesurf's daft imaginings in
uk.rec.audio.

I gather he's an 'academic'. I found this recently from some 'academics' and to
think this is what they're teaching for degrees !

" Audio systems are designed such that the output from the amplifier is matched
to the impedance presented by the speaker. This maximizes power output, and
mimizes reflection between the two.

The same principle applies to microwave systems; we want the output of a source
to be matched to the input of the next stage. If two components are connected
(e.g. a transmission line to an amplifier), there will be a reflection if their
impedances are unequal, reducing power transfer. "
http://bmf.ece.queensu.ca/mediawiki/...he_Smith_Chart

This wasn't even the case in the days of tube amps where the 'impedance
selector' simply presented the right tap for optimum output vs plate
dissipation.

FYI I left University College London's EE course after a year since I could see
most of the lecturers were totally out of touch with reality. Luckily I found a
better course later.

Graham

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

[Phil Allison[_3_]]

"Eeyore"


Maybe you'd like to join my crusade about Jim Lesurf's daft imaginings in
uk.rec.audio.

I gather he's an 'academic'.


** Jim is a former member of the academic staff ( means now dead wood ) at
the University of St Andrews where John Cleese ( of Faulty Towers fame)
was the Rector between 1970 and 1973.

Founded in 1410, the university also still has a thriving faculty of
Divinity - god knows why !!

The Science faculty allegedly gives out degrees in golf physics.

Not an engineer in sight .....




..... Phil

[Dave]

Phil Allison wrote:
"Eeyore"

Maybe you'd like to join my crusade about Jim Lesurf's daft imaginings in
uk.rec.audio.

I gather he's an 'academic'.


** Jim is a former member of the academic staff ( means now dead wood ) at
the University of St Andrews where John Cleese ( of Faulty Towers fame)
was the Rector between 1970 and 1973.

Mr. Cleese is likely ca. 60 miles due west of me right now.

[Ian Iveson]

Bob Eld wrote:

Posted by Jim Lesurf on uk.rec.audio:

"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."

Wadya think?

Pure unadulterated nonsense of zero meaning or
consequence. Maybe you didn't
realize it but audio frequencies are ALL below 100kHz.
Your measurements are
in the megahertz range.

Jim, not me.

Jim Lesurf. He writes for Hi-Fi News.

My view is that there is pretty much nothing left to write
about, so the comics compete to write about nothing.

What possible effect do they convey to sound
quality? Be imaginative in your explanation we're all
ears!

Imaginary rather than imaginative, I'm afraid. Although he
doesn't say so in the article, he has defended it by saying
it was intended to be a "heads up" to amplifier designers.
The concern, he claims, is that some amps may be inclined to
instability, and that this condition might be exacerbated by
some cables. He is unable to cite any such amplifiers in
reality, and doesn't say why publication in HFW is a
legitimate conduit for such a warning, or why the warning
isn't mentioned in the article itself. I could add that any
designer stupid enough to need warning about the need for
unconditional stability wouldn't be any the wiser after
reading it.

He also says he's concerned that amplifiers with relatively
high output impedance may be particularly susceptible to
some consequence or other, but this line of defense seems to
disappear into hand-waving and
if-you-don't-know-by-now-you-never-will snootiness.

But don't take my word for it, have a look over at uk.r.a. I
was dismissed as a troll, I'm afraid. I can see why,
although it's something of a misuse of the term. Considering
he's a professional writer, I'm disinclined to educate him,
so I just took the ****. It's not easy to argue against
determined nonsense anyway, which is exactly what the
snake-oil merchants rely on. Watch your ankles, there's a
couple of nasty poodles.

Finally, he is concerned that audio engineers without his
experience of working with high frequencies may not
understand what he's on about.

So, I wonder, is there anyone here who found the charts he
produced, using his fancy-pants machine "intended for
another purpose", in any way enlightening? Is there anything
there that you wouldn't expect, following a moment's
thought?

It's occured to me that I don't think anyone has used the
word "significant". That might be a question worth asking:
"Apart from the red herring about stability, what is the
significance of whatever effects you are on about?" He's not
going to listen to me, so someone else will have to ask.

I'm going on about this because I am genuinely outraged, and
embarassed to be English in the company of audio
enthusiasts. English engineers have always been snooty and
lacking in culture, but now they're mostly daft as brushes,
to boot.

Incidentally, has anyone been to rec.audio.tech recently? I
was going to post there but someone must have really upset
the spambots

Ian

[Phil Allison[_3_]]

"Ian Iveson"
Bob Eld wrote:

Posted by Jim Lesurf on uk.rec.audio:

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

Jim Lesurf. He writes for Hi-Fi News.

My view is that there is pretty much nothing left to write about, so the
comics compete to write about nothing.

What possible effect do they convey to sound
quality? Be imaginative in your explanation we're all ears!

Imaginary rather than imaginative, I'm afraid. Although he doesn't say so
in the article, he has defended it by saying it was intended to be a
"heads up" to amplifier designers. The concern, he claims, is that some
amps may be inclined to instability, and that this condition might be
exacerbated by some cables. He is unable to cite any such amplifiers in
reality, and doesn't say why publication in HFW is a legitimate conduit
for such a warning, or why the warning isn't mentioned in the article
itself. I could add that any designer stupid enough to need warning about
the need for unconditional stability wouldn't be any the wiser after
reading it.


** While it is possible for some hi-fi amplifiers to become unstable because
of the use of a high parallel capacitance speaker cable - the shame here
is there are NO such examples in the list of cables that Lesurf tested
!!!!!

ALL the cables in his list are low capacitance types ( ie figure 8 types )
hence quite benign and can be used with any amp and over any length. The one
example that is not figure 8 ( the Isolda ) has feed inductors fitted at the
amplifier end by the makers rendering it particularly benign.

Lesurf is CRYING WOLF in a similar way to notorious charlatans like
Matti Otala in 1973 with his phoney " TIM " distortion and Jung and Marsh in
1980 with their phoney ideas on selecting capacitors for audio.

The harm done to honest audio manufacturers by the latter complete nonsense
was enormous and is still going on today - with an army of net based snake
oil merchants flogging exotic capacitors and phoney up-grade kits for
amplifiers to fools.

My " heads up " to pseudo-science types like Lesurf, who feel compelled to
pontificate on the world of hi-fi audio, is that when deciding to CRY WOLF
to the world - be sure you are not just making technical howlers.




...... Phil

[Paul Keinanen]

On Sat, 15 Aug 2009 04:38:33 +0100, "Ian Iveson"
wrote:

Bob Eld wrote:


What possible effect do they convey to sound
quality? Be imaginative in your explanation we're all
ears!

Imaginary rather than imaginative, I'm afraid. Although he
doesn't say so in the article, he has defended it by saying
it was intended to be a "heads up" to amplifier designers.
The concern, he claims, is that some amps may be inclined to
instability, and that this condition might be exacerbated by
some cables.

The standard practice in audio power amplifier design for at least 35
years to put a parallel connected RL filter at the amplifier output.
This is usually implemented by using a few ohm a few watt resistor and
wind a few turns around this "core" and connect it in parallel with
the resistor and connect it between the actual amplifier output (from
which the feedback is actually taken) and the speaker terminal.

At low (audio) frequencies, the inductance of the few turns have no
practical effect, but at ultrasound frequencies, the inductive
reactance is high and the impedance is dominated by the resistor,
effectively isolating the load from the feedback loop, which otherwise
could cause instability.

Electrostatic loudspeakers are practically pure capacitive reactance
at high frequencies, causing potentially stability problems, unless
there is some isolation between the feedback loop and load at
ultrasound frequencies. Also some special loudspeaker cables with
artificially high capacitance could cause stability problems without
the filter.

He is unable to cite any such amplifiers in
reality, and doesn't say why publication in HFW is a
legitimate conduit for such a warning, or why the warning
isn't mentioned in the article itself. I could add that any
designer stupid enough to need warning about the need for
unconditional stability wouldn't be any the wiser after
reading it.

Some especially "high-end" manufacturers seems to be keen on
displaying how well the amplifier is reproducing a 20 kHz square wave.
In order to produce such a waveform purely, the amplifier must have a
good amplitude and phase accuracy at odd harmonics (60, 100 etc. kHz).
With a properly RL output filter, the amplifier is _not_ going to
produce a clean 20 kHz square wave, no matter how good the amplifier
itself is.

In order to get a clean square waveform, some "high end" manufacturers
omit this output filter, causing stability problems with difficult
loads and hence sound coloration when high capacitance speaker cables
are used.

In order to produce a clean square wave, some "high-end" manufacturers
also omit the input filtering, allowing potentially very steep input
signals, which the amplifier can not handle due to slew rate
limitation, driving the input stage into saturation and generating
TID.

In a proper power amplifier input there should be (before any feedback
stages) a low pass filter attenuating ultrasound signals in order to
avoid slew rate limitation effects as well as avoiding EMC problems
due to high field strength RF breakthrough, which could be rectified
in a small signal stage and there would be audio breakthrough from a
local AM radio station.

Some "high end" manufacturers have some special features that they are
keen of, emphasizing it to a point that good engineering practice is
ignored in other points of the design.


He also says he's concerned that amplifiers with relatively
high output impedance may be particularly susceptible to
some consequence or other, but this line of defense seems to
disappear into hand-waving and
if-you-don't-know-by-now-you-never-will snootiness.

If the amplifier has a high output impedance, this is a sign of low
(or non-existing feedback) so at least there should not be no
stability issues :-).


So, I wonder, is there anyone here who found the charts he
produced, using his fancy-pants machine "intended for
another purpose", in any way enlightening? Is there anything
there that you wouldn't expect, following a moment's
thought?

Those curves are of interest when you are trying to use some random
conductors e.g. speaker cables to run Ethernet or other high speed
signals. Unfortunately Ethernet over speaker cable (or Ethernet over
barbed wire :-) would use more sensible termination impedances.

Of course the impedance charts are quite as expected for a mismatched
transmission line, when the cable effective length is greater than
about 1/10 of the free space wavelength.

Paul

[Phil Allison[_3_]]

"Paul Keinanen"

** Sci fi is right on the money with this dude.


The standard practice in audio power amplifier design for at least 35
years to put a parallel connected RL filter at the amplifier output.
This is usually implemented by using a few ohm a few watt resistor and
wind a few turns around this "core" and connect it in parallel with
the resistor and connect it between the actual amplifier output (from
which the feedback is actually taken) and the speaker terminal.

** Correct.

At low (audio) frequencies, the inductance of the few turns have no
practical effect, but at ultrasound frequencies, the inductive
reactance is high and the impedance is dominated by the resistor,
effectively isolating the load from the feedback loop, which otherwise
could cause instability.


** Only if some dope puts an actual capacitor of the right value across the
output terminals.


Electrostatic loudspeakers are practically pure capacitive reactance
at high frequencies,

** Not all of them show a sudden impedance drop to very low ohms at high
audio frequencies - the famous Quad ESL63 and it close relatives are
notable exceptions.

http://www.quadesl.com/graphics/quad..._impedance.jpg


causing potentially stability problems, unless
there is some isolation between the feedback loop and load at
ultrasound frequencies.

** WRONG - the impedance dip is never in the supersonic range.

It is very much in the audible range where almost any amp made is perfectly
stable.


Also some special loudspeaker cables with
artificially high capacitance could cause stability problems without
the filter.


** High capacitance in the cable is the only potential issue - but it has
got to be damn high like 2000-3000 pF per metre.

No such troublesome cable was presented by Lesurf.


Some especially "high-end" manufacturers seems to be keen on
displaying how well the amplifier is reproducing a 20 kHz square wave.
In order to produce such a waveform purely, the amplifier must have a
good amplitude and phase accuracy at odd harmonics (60, 100 etc. kHz).
With a properly RL output filter, the amplifier is _not_ going to
produce a clean 20 kHz square wave, no matter how good the amplifier
itself is.

In order to get a clean square waveform, some "high end" manufacturers
omit this output filter, causing stability problems with difficult
loads and hence sound coloration when high capacitance speaker cables
are used.

** Even with no output inductor, the speaker load is never an issue.

Even with a ( now rare or impossible to find) very high capacitance cable,
any resulting instability is in the RF range.


In order to produce a clean square wave, some "high-end" manufacturers
also omit the input filtering, allowing potentially very steep input
signals,

** From where ??????????????

Space aliens singing in ultrasound on Blue Ray audio DVDs ???


which the amplifier can not handle due to slew rate
limitation, driving the input stage into saturation and generating
TID.


** ABSOLUTE CRAPOLOGY !!!!


If the amplifier has a high output impedance, this is a sign of low
(or non-existing feedback) so at least there should not be no
stability issues :-).

** Correct.

But none of the cables Lesurf presented would upset ANY amplifier.


Of course the impedance charts are quite as expected for a mismatched
transmission line, when the cable effective length is greater than
about 1/10 of the free space wavelength.

** BTW:

Do you buy the quoted 0.22C speed figure for the Isolda flat cable ??

Does not compute with the known dielectric constant for polyester insulation
( 4.1 to 5.2 ) as used by the makers " Townshend".



...... Phil

[PeterD]

On Fri, 14 Aug 2009 16:39:56 -0700, dave wrote:

Phil Allison wrote:
"Eeyore"

Maybe you'd like to join my crusade about Jim Lesurf's daft imaginings in
uk.rec.audio.

I gather he's an 'academic'.


** Jim is a former member of the academic staff ( means now dead wood ) at
the University of St Andrews where John Cleese ( of Faulty Towers fame)
was the Rector between 1970 and 1973.

Mr. Cleese is likely ca. 60 miles due west of me right now.

How is he doing? (If you know). Any public performances?

[Paul Keinanen]

On Sat, 15 Aug 2009 16:16:55 +1000, "Phil Allison"
wrote:


"Paul Keinanen"


Some especially "high-end" manufacturers seems to be keen on
displaying how well the amplifier is reproducing a 20 kHz square wave.
In order to produce such a waveform purely, the amplifier must have a
good amplitude and phase accuracy at odd harmonics (60, 100 etc. kHz).
With a properly RL output filter, the amplifier is _not_ going to
produce a clean 20 kHz square wave, no matter how good the amplifier
itself is.

In order to get a clean square waveform, some "high end" manufacturers
omit this output filter, causing stability problems with difficult
loads and hence sound coloration when high capacitance speaker cables
are used.

** Even with no output inductor, the speaker load is never an issue.

Even with a ( now rare or impossible to find) very high capacitance cable,
any resulting instability is in the RF range.


In order to produce a clean square wave, some "high-end" manufacturers
also omit the input filtering, allowing potentially very steep input
signals,

** From where ??????????????

Space aliens singing in ultrasound on Blue Ray audio DVDs ???

From a signal generator of course :-) and the signal output is viewed
on an oscilloscope. This is how many amplifiers were advertized and
apparently some audio amplifiers still appears to be designed in this
way.

which the amplifier can not handle due to slew rate
limitation, driving the input stage into saturation and generating
TID.


** ABSOLUTE CRAPOLOGY !!!!

In the 1960's many designers had discovered that even a bad design
could get very impressive performance figures by applying plenty of
feedback. The drawback was that some additional voltage amplification
stages was required, but since the cost of transistors had dropped
significantly, so adding a few voltage amplification stages was not a
cost issue (as it had been in the tube era).

In order to make many of these designs stable, quite conservative
frequency compensation had to be used, making the amplifier quite
slow.

A typical power amplifier has a differential pair in the input with
quite significant open loop gain. A steep transition at the input
could drive the input transistor out of range, before the slow global
feedback would bring the differential pair into linear operation.

Fortunately, this problem can be solved by making each stage
sufficiently linear by using local feedback so that excessive global
feedback is not required. At the differential pair input stage, adding
some emitter degradation resistors is often enough.

Of course, the input voltage slave rate must be limited by a low pass
filter to less than the output slew rate capability divided by the
closed loop voltage gain.



Of course the impedance charts are quite as expected for a mismatched
transmission line, when the cable effective length is greater than
about 1/10 of the free space wavelength.

** BTW:

Do you buy the quoted 0.22C speed figure for the Isolda flat cable ??

Does not compute with the known dielectric constant for polyester insulation
( 4.1 to 5.2 ) as used by the makers " Townshend".

Yes, those figures looked quite strange.

I have used microstrip resonators on PCBs ("infinite" ground plane
and a strip with a well controlled width in an other layer) both
below and above 1 GHz, in which the velocity factor (and hence
required resonator length) is assumed to be constant at least for a
specific line impedance (typically 50 ohms). However, looking at some
reference documents, the velocity factor drops by some tens percent at
very low impedance levels (= wide signal conductors).

The Isolde cable has a ground plane with the same width (15 mm) as the
signal conductor (not infinite ground plane as in microstrips) so this
might also affect the quite low propagation velocity.

Looking at the impedance chart for the 5 m section, the 1/4 wave
resonance (both open and short) at 3.2 MHz would rule out any lumped
capacitance hiding inside the cable. The frequency is consistent with
a velocity factor of 0.2-0.25.

The listed inductances and capacitances would also be consistent with
the claimed velocity factor and impedance.

Looking at the huge capacitance of 2800 pF/m for a 15 mm wide strip,
would suggest about 0,2 mm insulation between the conductors, if er=5.

To make a home brew Isolde cable, take a 15 mm long tubular capacitor,
cut it open and unroll the foil and at both ends, attach banana plugs
to the both foils :-). You may have to add some mechanical
strengthening to it.

Paul

[Fu Knee]

Hi RATs!

Some geezer gets a little cash for a silly article in an audio
advertising rag and you lot get huge erections ... the rockers on your
hobby horses are bent, strangely.

"A concise history of the Great Wars of the Aural Age of
Enlightenment ..." such depth of field!

Whatever gets you through the long, dark, teatime of the soul - August
in London.

Happy Ears, my snarling friends,

Al

[Phil Allison[_3_]]

"Fu Knee"

Some geezer ..

** A famous audio industry person, former university academic and dominant
member of the newsgroup " uk.rec.audio".


gets a little cash for a silly article in an audio advertising rag


** That event never caused at a murmur - as no-ne on the NG reads the rag.

Publishing the same bogus info on the NG and thereby inviting comment was
what did it.


and you lot get huge erections ...


** Physical impossibility, for any of the rabid, needle dick poms that
haunt "uk. rec.audio".


Happy Ears, my snarling friends,


** Remember: on usenet -

NO-ONE CAN HEAR YOU SCREAM !!



....... Phil

[Ian Iveson]

Al ventured:

Some geezer gets a little cash for a silly article in an
audio
advertising rag and you lot get huge erections ... the
rockers on your
hobby horses are bent, strangely.

"A concise history of the Great Wars of the Aural Age of
Enlightenment ..." such depth of field!

Whatever gets you through the long, dark, teatime of the
soul - August
in London.

Happy Ears, my snarling friends,

http://www.bigeye.com/donotgo.htm

Ian

[[email protected]]

On Aug 14, 9:52*am, "Ian Iveson"
wrote:

Wadya think?

Mpffff.....

I think that straightened steel coat-hangers, if properly insulated
and terminated will do just fine for 99-44/100ths of typical
applications.

That I use standard #12 stranded THHN wire spun in a drill (for ease
of handling, not for any magic electrical properties due to spinning)
is because it is cheap, tough, can be pulled through walls without
damage and is amenable to longish runs - such as to my rear speakers
in the library - 35 foot runs.

"Difficult loads" - that would be the speaker, perhaps? Doncha think?

I guess one gets what one pays for - and if one pays enough for a
'difficult load', it will be produced as needed.

YIKES!

Peter Wieck
Melrose Park, PA