On 2009-08-07, Eeyore wrote:

John Phillips wrote:

On 2009-08-07, Don Pearce wrote:
On Fri, 07 Aug 2009 09:10:40 +0100, 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. Out of the audio band this gets no better,
from what I have seen.

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.

--
John Phillips

In article , John Phillips
wrote:


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.

Indeed. In fact there are two stages to this.

1) The designer has to be able to establish if his bench design is
unconditionally stable or not. And if not, modify or change, to obtain
unconditional stability, without fouling the performance in some other way.

2) To then ensure that this will be true for commercial versions made with
components with a tolerance spread of values, slight alterations in
wirings, etc.

The worry here is the 'WW' effect. That of designs where a prototype
(published in Wireless World for example) worked fine for the designer. But
when many readers make 'clones' some of them oscillate or misbehave in use
due to changes in precise component values, wiring, etc. Hence the old term
'a WW design = a Worked Wunce design' to refer to this possibility. :-)

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

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.

There are two aspects of this that have concerned me. One is that I am far
from certain if all current/recent commercial designs are unconditionally
stable - particularly as I don't see signs that any reviews routinely check
this.

The other is the lack of any info on what speakers do above the audio band.
When you then throw in a variety of types and lengths of cables, almost
anything could happen in some cases.

I chose to measure an LS3/5A as I had a pair to hand. No idea what other
speakers do above the audio range. There seems to be zero data. I doubt the
makers usually know or care.

BTW Given Eeyore's reaction I'd suggest people read the previous two
'cables' articles in the series as that did cover some points. e.g. the use
of output networks. Although more about this and other factors will be in
later articles.

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

"John Phillips"

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.


** Fraid that is absolute crap.

Only a FAULTY speaker exhibit shorts or opens in the audio band.


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.


** Only if you are a pseudo academic, audiophool lunatic.

Cap fits you OK.



..... Phil

Phil Allison wrote:
"John Phillips"
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.


** Fraid that is absolute crap.

Only a FAULTY speaker exhibit shorts or opens in the audio band.

How about this, the only impedance curve on Trevor's site?
http://www.rageaudio.com.au/index.php?p=1_12

--
Eiron.

Eiron wrote:

Phil Allison wrote:
"John Phillips"
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.

** Fraid that is absolute crap.

Only a FAULTY speaker exhibit shorts or opens in the audio band.

How about this, the only impedance curve on Trevor's site?
http://www.rageaudio.com.au/index.php?p=1_12

I can barely believe how anyone could have produced such a diabolical
impedance curve.

The alleged 0.8 ohms at 30 something Hz is especially odd. I suspect
negligent design of the crossover too. Par for the course for audiophools.

Note that the impedance doesn't peak over 9 ohms.

Graham

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

"Eiron"
Phil Allison wrote:
"John Phillips"
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.


** Fraid that is absolute crap.

Only a FAULTY speaker exhibit shorts or opens in the audio band.

How about this, the only impedance curve on Trevor's site?
http://www.rageaudio.com.au/index.php?p=1_12


** TW drags that absurd, false example up as a marketing ploy for a brand of
amp he supplies.

In fact and as he admitted once, the impedance dip at the low end of the
range ( circa 35Hz) was due to a wiring MISTAKE made by the factory in a
few samples sold only.

Cause havoc with owners amplifiers blowing fuses and output devices until
they had them fixed.



...... Phil

Phil Allison wrote:
"Eiron"
Phil Allison wrote:
"John Phillips"
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.

** Fraid that is absolute crap.

Only a FAULTY speaker exhibit shorts or opens in the audio band.
How about this, the only impedance curve on Trevor's site?
http://www.rageaudio.com.au/index.php?p=1_12


** TW drags that absurd, false example up as a marketing ploy for a brand of
amp he supplies.

In fact and as he admitted once, the impedance dip at the low end of the
range ( circa 35Hz) was due to a wiring MISTAKE made by the factory in a
few samples sold only.

Cause havoc with owners amplifiers blowing fuses and output devices until
they had them fixed.

Thanks for the correction.
So the only reason for buying an ME 850 is to drive a broken Infinity Kappa. :-)

--
Eiron.

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.


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

Graham


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

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

"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