On Fri, 07 Aug 2009 10:40:08 +0100, Jim Lesurf
wrote:
In article 4a7be630.269829187@localhost, 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.
Slainte,
Jim
No conclusions section there, but maybe as follows?
There are a couple of 'follow on' articles which I wrote a while ago but
are currently unpublished. At present I'm deciding what to do with them.
Put them directly onto the web, or see if a magazine wants them first. When
they appear the 'conclusions' may be a bit clearer.
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.
In general, cable losses will reduce the amplitude in the presented
impdance changes with frequency in the RF region. The snag being that if
too large, they could also upset performance in the audio region.
I can think of certain brand amplifiers which would sing a loud and
shrill song to such a load.
IIUC one aspect of DNM's argument is that his cables do include RF loss.
(My interpretation of what he says is this is due to internal impedance as
the cable uses solid core wire. Thus introducing a loss at RF.)
I can't see that impedance per se introduces loss. Maybe he meant
resistance. Do you suppose he was talking solely about skin effect, or
does he use a particularly lossy dielectric?
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).
Yes, although I'd qualify that as below...
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.
The inductor (and LS end load) are to deal with the loading at RF. If you
look, without these the dips go *very* low. That might upset poor amplifier
designs which don't have unconditional stability, or, say, whose distortion
behaviour could be affected. You'd need to check with Max, but my
understanding is that the networks are included as standard with lengths of
their cable. Although if you know your amp isn't fussed by a severe RF dip
or resonances then I'd say you could dispense with them.
Ok, I can see that. The inductor is taking the place of the one that
should really already be inside the amplifier. And of course being low
loss and low Z, this cable will invert the high Z speaker resonances
very nicely into an extremely low Z dip. If only speakers were
resistive, we could avoid all this - sigh.
FWIW I like the technical performance of the Isolda. But I'd find it a PITA
to use as you have to take care laying it out, etc. However if you have
very long, essentially straight, cable runs, it should do the job well.
Apart from the above, I've continued to use the Maplin 'monster cable' for
my own systems. But the runs are only a couple of metres.
Same distance here, but I haven't bothered with the sophistication of
Maplin cable. I just use some old wire from the junk box.
d