"Patrick Turner"
"Phil Allison"

Jim Lesurf wrote:

http://www.st-andrews.ac.uk/~www_pa/...g/howlong.html

Doing the usual maths on your table of cables

A = 8.5

** Cable "A" would be a woven multi-strand cable like "Tocord" - it
was
sold under other names too.

** I have placed a pic of a " Tocord " speaker lead on ABSE - since I
could not find one on the net.

There are 72 green and 72 copper coloured strands - each enamel coated
so
are all insulated. There is a central clear plastic core ( not visible in
the pic) of about 4mm diameter which the 144 strands are woven around.
The
outer sheath is only 7mm diameter and so the cable is quite flexible.

In order to fit a termination like the banana plugs shown, one must first
burn off the enamel coating with a hot soldering iron and lots of solder.



I doubt I'd ever wanna use that Tocord cable.


** Look out -

here comes a whole pile of "Turneroid" hypothetical, fabricated drivel !!!


If someone crushes the cable under a foot or something, then it'd
be easy to get a short between the different colour enamel wires woven
together.


** Simply not true.

The strands of enamelled wire are very tough and well protected by the outer
sheath and inner, soft plastic core.


And if the enamel wire can be tinned with a hot soldering iron, then its
fragile enamel,


** That is complete ********.


Most SS amps are made to tolerate pure C loads from say 0.002uF to 0.22
uf because


** And some are not - particularly some UK made hi-fi exotica.

But the problem is easy fixed by adding a small coil in series with the
amplifier's output.

20 turns of 1mm enamel wire wound on a pencil will do.



...... Phil

In article , Don
Pearce
wrote:
Jim Lesurf wrote:
A while ago there was some discussion about loudspeaker cables and the
relative merits of analysis using the transmission line and AC lumped
element approachs. I've now done a page on this which people may find
interesting. It is at

http://www.st-andrews.ac.uk/~www_pa/...g/howlong.html


Thanks for that, Jim. Pretty much what I expected, with the (for many
counter-intuitive) result that the high capacitance cable had the
flattest response - the expected result of having a better
characteristic impedance match. Doing the usual maths on your table of
cables

A = 8.5 B = 176 C = 153 D = 59 E = 211 G = 48.76

So as far as top end flatness goes, characteristic impedance is the best
predictor of performance.

That is OK if your concern is well above 20kHz for "top end". However the
actual cable impedances are well away from the approximate values you quote
at or below 20 kHz and the behaviour is better predicted there by series
inductance and resistance than by the above nominal values for
characteristic impedance. As the HFN articles will detail... :-)

Despite high capacitance, which might be
thought of as predicting a sagging top end, the high cap cable (A) at
8.5 ohms impedance is the only cable which is actually flat. And of
course a further implication of this is that this cable does not
present a capacitive load to the amp - it connects the speaker almost
invisibly, presenting the speaker impedance to the amp essentially
unchanged.

I'm afraid you make the classic oversight of assuming behaviour is close to
matched. It simply isn't. The reality is simpler. That low series impedance
gives you the flat response in these sorts of situations when the
frequencies are around 20 kHz or less.


And of course this is for cables of 5 metres. There are many audio apps
that use cable considerably longer than this, which makes it important
to think about the applicability of models.

The interest I have is for domestic audio. I doubt that more than a small
fraction of those use cables an order of magnitude longer than 5 metres.

Slainte,

Jim

--
Change 'noise' to 'jcgl' 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

Jim Lesurf wrote:

A while ago there was some discussion about loudspeaker cables and the
relative merits of analysis using the transmission line and AC lumped
element approachs. I've now done a page on this which people may find
interesting. It is at

http://www.st-andrews.ac.uk/~www_pa/...g/howlong.html

Note that I decided to put this on the Scots Guide not AudioMisc. This is
because the page shows a fair bit of 'hard sums' - i.e. the algebra for the
two approaches. However even if hard sums make your head ache, the results
may be of interest. :-)

Yes, always been interested in this. I will peruse. Thanks for doing the hard
work.

Graham

"Jim Lesurf" wrote in message
...
A while ago there was some discussion about loudspeaker cables and the
relative merits of analysis using the transmission line and AC lumped
element approachs. I've now done a page on this which people may find
interesting. It is at

http://www.st-andrews.ac.uk/~www_pa/...g/howlong.html

Note that I decided to put this on the Scots Guide not AudioMisc. This is
because the page shows a fair bit of 'hard sums' - i.e. the algebra for
the
two approaches. However even if hard sums make your head ache, the results
may be of interest. :-)


**Nice work Jim. It backs up what I've been telling people for a couple of
decades. As Phil has stated, what would be interesting would be to do the
same analysis with real-world speakers. Particularly ESLs. I've measured one
pair which has a response that falls to less than 1 Ohm at about 17kHz. Low
inductance cables tend to be essential with such speakers.


--
Trevor Wilson
www.rageaudio.com.au

In article , Trevor Wilson
wrote:


**Nice work Jim. It backs up what I've been telling people for a couple
of decades. As Phil has stated, what would be interesting would be to
do the same analysis with real-world speakers.

I am creeping up on that. :-) The webpage does show results for 4 - 32
Ohms resistive to indicate that any resistive load value which is broadly
similar to a speaker doesn't change the conclusions much. The page was just
to make the basic point and show the analysis methods.[1] However...

The HFN articles use a series of loads - resistive, capacitive, inductive,
as well as open and short. They compare measurement with theory and get
suprisingly good agreement. I also ended up including things like 'internal
impedance' (aka skin effect) and how it alters the behaviour of cables

I am also in the process of examining the use of squarewaves, and the use
of a load more like a speaker. i.e. one with a complex impedance that has
some peaks and dips.

However for obvious reasons I have broken this up over a series of
articles. All too much for just 3-4 A4 pages! The measurements also took
weeks to do and analyse. The webpage just uses old results by other people,
but I have done my own measurements on various cables, and details should
appear in due course. In fact, there is so much that as with some previous
articles I will probably end up doing 'extended' versions on the web six+
months after the magazine version appears.

FWIW The first HFN article should appear in the next issue. Now seen and
checked a PDF of the page layout. The other articles will appear in
following months, but there will be some breaks and diversions for articles
on other topics.

BTW Although I chose the cables 'at random' from a long list I compiled it
seems clear that 'A' was the old 'Monitor Audio' branded cable claimed to
be '8 Ohm'. For that, the values I have were measured by Jim Moir and
published in HFN. Detailed references in the articles.

Slainte,

Jim

[1] One reason for the webpage is that is will allow me to give it as a
reference if I wish in a magazine article. I wanted readers who are
interested to be able to see the models I used, but to avoid putting 'hard
sums' into the magazine and making the actual article difficult for those
who don't like maths. Given the models anyone else can - if they wish - do
similar work with other loads, cable lengths, etc, etc.

--
Change 'noise' to 'jcgl' 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

"Jim Lesurf"

A while ago there was some discussion about loudspeaker cables and the
relative merits of analysis using the transmission line and AC lumped
element approachs. I've now done a page on this which people may find
interesting. It is at

http://www.st-andrews.ac.uk/~www_pa/...g/howlong.html


** Figure 4 shows the " lumped component " model of a speaker cable that Jim
used.

But why the heck is C shown at the speaker end and so coming AFTER the
cable's inductance ???

Any cable ( whether co-axial, twin wire, twisted pair or woven pair )
exhibits pure capacitance when the far end is not loaded. So C ought to be
at the input end - then at least the cable model would pass open and short
circuit load testing.

In fact, the model as shown in fig 4, resolves to simply cable L plus R in
series with a pure 8 ohm load - over the frequency range graphed - cos
the 8 ohm load completely swamps the effect of the C values involved.




...... Phil