New webpage on loudspeaker cables
 

In article , Eeyore
wrote:


Jim Lesurf wrote:

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.

Then those are simply badly or incompetently designed. You'd be amazed
at some of the pure **** that has been sold as 'audiophile'.

Actually, no, I wouldn't be 'amazed' at all. :-) Indeed, that was one of
the main reasons for the work I did on cables. Because I know there is a
risk that some designs may oscillate or otherwise be affected by RF loads
produced by some load/cable combinations. And because I don't presume that
*all* designs on sale are unconditionally stable. Some may indeed, br 'pure
****'. But I can't tell because there is almost never a check on this in
reviews, etc.

Perhaps you should read the previous two articles I did on this. The recent
page follows on from them. The earlier articles do deal with things like
the use of an output network. You could also note tbat RF stablity wasn't
the only purpose of the measurements. They were also to determine the cable
RLCG values, which can affect aspects of performance like frequency
response in the audio band even for amplifier that are unconditionally
stable. :-)

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

New webpage on loudspeaker cables
 

In article , Eeyore
wrote:


John Phillips wrote:
to the many MHz region whenever I failed
to pay enough attention.

So, I'm surprised at your reaction elsewhere. Even in the audio band,
loudspeakers can present impedances from near zero to high enough to
be considered infinite.

WRONG. Show me one.

Perhaps you can direct me to a set of measurements on the input impedance
of domestic audio speakers that extends up to, say, 20MHz? I'd be very
interested to see if *anyone* has systematically measured these values and
published them.


Out of the audio band this gets no better, from what I have seen.

By which time the RLC network in the output stage will be doing its job,
so the point is academic.


So it seems to me that investigating loudspeaker cables with loads
from zero to infinity, and at frequencies well above the audio band,
is perfectly reasonable.

I do not remotely agree. For most speakers 4 - 60 ohms +/- 4 - 60 j ohms
would suffice.

I trust you know the meaning of the j

Pardon me for asking, but do you understand how a length of mismatched
transmission line can transform the presented load impedance? Thus allowing
quite large changes at RF?

Also, can you point me at a set of measurements of the kind I ask for
above? They may well exist, but I can't recall ever seeing any.

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

New webpage on loudspeaker cables
 

In article 4a800142.407830593@localhost, Don Pearce
wrote:
On Sat, 08 Aug 2009 19:58:06 +0100, Eeyore
wrote:



Jim Lesurf wrote:

Rob wrote:
Jim Lesurf wrote:

FWIW it means very little to me. You seem to assume a correlation
between frequency, resistance and sound.

Not sure what you mean, I'm afraid.

That much is apparent. Doubt you know much about the concept at all,
nor the bases of stability.


Can you explain then? It has me puzzled too. And given Jim's background
I am going to tell you he knows precisely what stability means, and how
to measure and predict it.

I guess I have had to deal with this in more ways than many engineers. From
designing audio power amps that were unconditionally stable to 90-300 GHz
oscillators where the precise details of the instability were critical to
the performance. :-)

I now wonder if some audio engineers simply aren't familiar with the
methods that are normal in RF/microwave.

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

New webpage on loudspeaker cables
 

On 2009-08-08, Eeyore wrote:
John Phillips wrote:
Eeyore wrote:
John Phillips wrote:
Don Pearce wrote:
Jim Lesurf wrote:

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.

Yes - I agree. It seems we are in harmony about the need for an amplifer
to see a well-defined load at frequencies well above the audio band. Hence
my use of "good quality inductance" which needs to avoid self-resonance
at too low a frequency to maintain isolation for whatever the user throws
at the amplifier in terms of cable and loudspeaker.

I learned a lot from designing and building my first power amplifier.
I saw undesirable behaviour into the many MHz region whenever I failed
to pay enough attention.

So, I'm surprised at your reaction elsewhere. Even in the audio band,
loudspeakers can present impedances from near zero to high enough to
be considered infinite.

WRONG. Show me one.

That's not relevant. In designing a power amplifier what's important is
the range of possible behaviours over as many 'speakers as the designer
wants to take into account - not just one.

I'm sure you know that and I'm puzzled why you choose to go down that
dead-end road when a little thought should prevail.

Out of the audio band this gets no better,
from what I have seen.

By which time the RLC network in the output stage will be doing its job, so the
point is academic.

That's true only in the consideration of load-related stability problem,
and then only in the case where the "usual" RLC network is present.
Having learned about the RLC solution to the problem I, for one, retain
the academic curiosity to learn how it might otherwise be done. Remember,
that's the way progress lies.

So it seems to me that investigating loudspeaker cables with loads
from zero to infinity, and at frequencies well above the audio band,
is perfectly reasonable.

I do not remotely agree. For most speakers 4 - 60 ohms +/- 4 - 60 j ohms
would suffice.

I guess you meant to write that differently since the minimum of that
range as written, (4 +/- 4j) Ohms, would only do for designing an
amplifier intended to drive loudspeakers labelled "8 Ohms" or above
(assuming the relevant DIN standard had been observed).

You might like to consider, for example, figure 4 from this page:
http://www.stereophile.com/features/99/index4.html.

I trust you know the meaning of the j

Graham, this style of argument is very reminiscent of another
contributor to this news group. It's not very helpful.

--
John Phillips

New webpage on loudspeaker cables
 

Jim Lesurf wrote:
In article , Rob
wrote:
Jim Lesurf wrote:

FWIW it means very little to me. You seem to assume a correlation
between frequency, resistance and sound.
Not sure what you mean, I'm afraid.


There's a relationship between three things: frequency and resistance
(the things you plot) and sound.

All the plots show relationships between frequency and apparent load
'resistance' (actually magnitude of impedance). But that isn't directly
related to 'sound' as such.


Ah fine, that was just my assumption relating to the point of the
article. I see now the point of your discussion is 'risk'. Or have I got
this wrong? There was no specific point - just a series of tests to see
what happens?

If one of the things change, another one will change ('correlation'). On
further reading you suggest a relationship between frequency, resistance
and risk.

As above. Sharp/deep dips in the 'resistance' as you change frequency tend
to give more 'risk' that the amplifier will be affected in a significant
manner. But this isn't a simple relationship with 'risk' as that depends on
'risk of what' and choice of amp, etc. Decent amplifier designs will be
essentially unaffected by all this. But some amps might be unhappy.

Perhaps a paragraph or two on what you might expect any measured
result in the context of your measurments to mean?
The measurements and results serve two purposes.

1) The size of the peaks and dips in impedance will vary with the
choice of cable and end-load (speaker). Using 'open' and 'short' means
loads with impedances as high and low as you can get compared with the
cable impedance. So you can expect the results to give you a guide to
which cables give the highest or lowest peaks/dips for real-world
loads. Hence the results give a sign of which cables would be more
risky with amplifiers that are not unconditionally stable, or whose
behaviour can be upset by RF resonances, etc. In particular, sharp
dips down to very low impedance can be bad news for a poor amplifier.
Hence useful as a warning.


Ah, OK, good. But is it *really* risky for any amplifier that doesn't
carry a cable recommendation tag? By risk I assume possibility of
component failure.

It is certainly possible for an amplifier to exhibit uncontrolled RF
oscillations, and for those to then damage the amplifier. Possibly also the
speaker. But I can't tell you any value for the 'risk' of this happening as
it would depend on things we don't know. More likely is that the audio
behaviour may be affected without the amp failing.


I'm sorry - lost here. You explained above that the relationships you
are examining are not related to sound 'as such'. Does 'as such' mean
'except when it is'? ;-)

I know you don't know everything about every amplifier, but could you
explain what the average punter should look for in an amplifier to avoid
these issues? The sorts of questions I can ask a manufacturer for example?

Again, well designed amplifiers aren't at any 'risk'. If the designer knew
what he was doing they will be stable into any load.

[snip]

It'd be nice, although I expect quite difficult, if you could explain
how these effects could influence sound.

Again, depends on the circumstances. High cable series impedance will alter
the frequency response in ways that depend on your choice of speaker.

High cable shunt capacitance may affect response if the amp has a high
output impedance (very low 'damping factor').

But the details will depend on the specific case. The alterations may be
too small to be bothered with, or not...


I know of course this is going completely left field, but could you give
real world examples (*an* amplifier*, *some* cable) when sound might be
affected? I suspect your interest is entirely theoretical, but and if I
may say you do appear reluctant to be drawn . . .

A *useful* theory is one that explains why something is happening. I
follow your theory development to a point, but I don't understand what
use your findings are (exception noted below, remove possibility of
problems) if they're not 'latched' on to real world scenarios.

There are a couple of follow-on articles, that do look at this
further, and include simple techniques - like the use of a series
inductor and 'zobel' on the amp to help protect it against (1). That
is a method I've always used as it works neatly. But there are
commercial amplifier designs that *don't* do this, so are exposed to
RF loading by the cable and speaker.

Sounds daft. Do you know which amplifiers?

I can't comment on any current or recent commercial designs as I've not
measured them, and reviews generally ignore this area. So no data. I think
it likely that most (indeed almost all) are fine as this should be a known
problem, and engineers determined how to fix it decades ago. Maybe they are
all fine. But... no data.

However I do tend to get an uneasy feeling when reviews ignore issues like
this for decades. It can mean eyes are not on the ball and problems
familiar to past generations of engineers may end up in new designs because
no-one is alert. I confess I do wonder when I see some of the more 'quirky'
designs sold at high prices that have all kinds of of characteristics.

I can only say that I've personally seen such effects in amps many years
ago. e.g. in the Naim amps of some decades ago. It is a common problem with
experimental designs which the designer then has to iron out.

The problem here is that it can make good sense to choose loudspeaker
cables with very low series resistance and inductance, but that this means
high capacitance with minimal damping losses, and unless the amplifier is
happy with this there may be drawbacks.


Yes, I think *that's* a good point - remove the possibility of trouble
ahead, however remote that possibility.

In our universe, the product of series inductance and shunt capacitance for
cables is limited by the speed of light. Lowering one tends to shove up the
other. To avoid this, invent warp drive, or use a wormhole in space for the
cable. ...or just keep down the length of cable needed. :-)


Noted :-)

Rob

New webpage on loudspeaker cables
 

Jim Lesurf wrote:

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.

Thank heavens for Hi Fi News.

Of course I rushed out to buy my wonderful Isolda cables
immediately. With the old Maplin leads, *anything* might
have been happening. After all, some amplifiers have some
problems with some other cables, and since we don't know
which amplifiers, or what problems, or which cables, it's
better to be on the safe side.

Treated myself to a matched pair of Cosmic Flux Pyramids,
just to be sure.

Ian

New webpage on loudspeaker cables
 

"John Phillips = Pommy ****"

Even in the audio band,
loudspeakers can present impedances from near zero to high enough to
be considered infinite.

WRONG. Show me one.

That's not relevant.


** It was YOUR damn stupid claim - ****head !!

Soooooo *** YOU *** get to prove it OR else

be considered by ALL as yet another lying, pommy TURD.



In designing a power amplifier what's important is
the range of possible behaviours over as many 'speakers as the designer
wants to take into account - not just one.

** Giant HUH !!!!

What sort of pseudo-logical, dishonest CRAP is that ????



That's true only in the consideration of load-related stability problem,
and then only in the case where the "usual" RLC network is present.
Having learned about the RLC solution to the problem I, for one, retain
the academic curiosity to learn how it might otherwise be done. Remember,
that's the way progress lies.


** Another GIANT HUH !!!

This TOTAL LOON must be one of them half-witted Star Trek fanatics -

with pointy ears and all - to match its pointy head.


So it seems to me that investigating loudspeaker cables with loads
from zero to infinity, and at frequencies well above the audio band,
is perfectly reasonable.


** No doubt Mr Spock would agree.


I guess you meant to write that differently since the minimum of that
range as written, (4 +/- 4j) Ohms, would only do for designing an
amplifier intended to drive loudspeakers labelled "8 Ohms" or above
(assuming the relevant DIN standard had been observed).
You might like to consider, for example, figure 4 from this page:
http://www.stereophile.com/features/99/index4.html.


** Figure 2 shows the impedance curve of a typical, 8ohm nominal, 2-way
speaker with minimum Z of about 7 ohms * resistive* at 250 Hz and a worst
case load phase angle of 45 degrees ( leading ) at 16 ohms and 80 Hz.

Easily driven, to full output level, by just about any amp ever made.


HOWEVER:

Figure 4 simply has no technical meaning whatsoever.

But IS a VERY NICE example of the MAXIM that says:

" There are lies, damn lies and ... statistics. "
-----------------------------------------------------

BTW:

Speaking about being " helpful "...

go help yourself to a kilo of rat bait.

ARSEHOLE !!!



.... Phil

New webpage on loudspeaker cables
 

"mick" wrote in message

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... ;-)

I agree.

New webpage on loudspeaker cables
 

"Ian Iveson"
Jim Lesurf Criminal wrote:

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.


Thank heavens for Hi Fi News.

Of course I rushed out to buy my wonderful Isolda cables immediately. With
the old Maplin leads, *anything* might have been happening. After all,
some amplifiers have some problems with some other cables, and since we
don't know which amplifiers, or what problems, or which cables, it's
better to be on the safe side.

Treated myself to a matched pair of Cosmic Flux Pyramids, just to be sure.


** That is almost funny.

Academic ****s like this " Jim Lesurf " character are a POX on the face of
the earth.

They think and write in a social vacuum, with a criminally reckless
disregard for the obvious consequences.

Other examples include:

1. Matti Otala , who did ENORMOUS HARM with his asinine, phoney " TIM
" bull****.

2. Walter Jung and Richard Marsh, who did ENORMOUS HARM with their
witchcraft like approach to using capacitors.

Both the above played RIGHT INTO THE SLIMY HANDS of a small army of
*scumbags and charlatans* who were just WAITING to exploit the fake
credibility these pukes writings provided them with.

Plus and as a DIRECT result, many honest and thoroughly expert designers
& makers of audio gear, all round the world, were almost or actually put out
of business.

PLUS:

Any IMBECILES who purchase audiophool speaker cables DESERVE to have
their stupid, audiophool amplifiers BLOW UP !!!

Only that might put the vile, cable scammers out of business.



..... Phil

New webpage on loudspeaker cables
 

In article ,
Phil Allison wrote:
Academic ****s like this " Jim Lesurf " character are a POX on the face
of the earth.

They think and write in a social vacuum, with a criminally reckless
disregard for the obvious consequences.

Other examples include:

1. Matti Otala , who did ENORMOUS HARM with his asinine, phoney "
TIM " bull****.

2. Walter Jung and Richard Marsh, who did ENORMOUS HARM with their
witchcraft like approach to using capacitors.

Both the above played RIGHT INTO THE SLIMY HANDS of a small army
of *scumbags and charlatans* who were just WAITING to exploit the
fake credibility these pukes writings provided them with.

As usual you have jumped straight in without reading and digesting the
article.

It is merely a series of test results. Unlike those from others designed
to sell some snake oil product. If you had actually read it you'd know
that any conclusions from the data come in a later article.

Plus and as a DIRECT result, many honest and thoroughly expert
designers & makers of audio gear, all round the world, were almost or
actually put out of business.

Some may have deserved to be.

PLUS:

Any IMBECILES who purchase audiophool speaker cables DESERVE to
have their stupid, audiophool amplifiers BLOW UP !!!

And articles like this might just help those see the error of their ways.

BTW, potty mouth, where is all your research published? Since you claim to
be such an expert in everything?

--
*If you remember the '60s, you weren't really there

Dave Plowman London SW
To e-mail, change noise into sound.