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

--
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

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.

Slainte,

Jim

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.

2. Provided you have a speaker on the far end, none of the cables
result in a particularly problematic load at RF. The minimum impedance
variations tend to come from the cables with lower characteristic
impedance (closest conductor spacing).

3. The Isolda behaves very differently to the rest, and provided it is
used as recommended, presents the most consistent and friendly load of
any.

I could do with some more info on the Isolda cable - what the inductor
is all about and how come the impedance drops so low without it.

d

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?

--
John Phillips

In article , John Phillips
wrote:
On 2009-08-07, Don Pearce wrote:


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?

That is the 'solution' I personally tend to prefer. It also helps deter
entry of RF into the amp via the live speaker lead.

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 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


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

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

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'.

Graham


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

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