In ,
harrogate2 typed:

It is nothing to do with the speaker load impedence, rather the amp
output impedence.

When the loudspeaker cone is extended by signal, if the signal is
removed then it is down to the mechanics of the cone mount to return
it to its rest position - except that it won't, it will follow a
decaying oscillation path. During this time, as the voicecoil is now
being moved mechanically in a magnetic field it becomes a generator,
so the lower the load that it sees - in this case the output impedence
of the amp plus cable resistance - the quicker the energy will be
dissipated. As an amp output impedence is typically around 0.1R (or
less sometimes) then the resistance of a thinner cable can become
significant, hence why thick is better.


I don't see that. In addition to the output stage of amp and cable the same
current is *also* flowing through the speaker coil itself, they are all in
series. Therefore it is in the speaker coil where most of the energy is
dissipated, assuming that the output impedance of the amp is, indeed, low.
And also assuming that the cable resistance is low compared to the speaker
impedance. It follows that the cable resistance should be low compared to
the *speaker* impedance because it is this that has the major effect on the
overall output circuit energy dissipation and hence damping factor.

I see the setup as being analogous to a generator with a short circuit on
the output terminals, or a very low resistance load. The windings of the
generator heat up and dissipate more energy than the load.

But I do agree that thick cable is better :-)

I used to have a pair of BIG transmission line loudspeakers that could
rattle windows at 10 paces with only a few watts! I used 6mm power
cable used in the mobile radio industry (where I work) and they were
more than happy. When we moved to this house I initially couldn't get
under the floor to run the bigger cables so I ran some 0.75mm mains
cable - and the sound was AWFUL!! Bloated flabby bass with
considerable loss of LF detail (amongst other things we like pipe
organ music, the penalty of having a father-in-law who is an
organist!) When I fitted the thicker cable normality was restored.


My speakers are IPL transmission lines and I'm minded to follow your example
and use cable with a really hefty cross section. Maplin are currently doing
a multistrand cable with a csa of 5.28 mm sq that is advertised as "HiFi",
OFC and all the hype, but at £1.49 /m looks as cheap as some similar power
cables.

Jo

On Mon, 6 Mar 2006 22:07:51 +0000 (UTC), "Jo"
wrote:

In ,
harrogate2 typed:

It is nothing to do with the speaker load impedence, rather the amp
output impedence.

When the loudspeaker cone is extended by signal, if the signal is
removed then it is down to the mechanics of the cone mount to return
it to its rest position - except that it won't, it will follow a
decaying oscillation path. During this time, as the voicecoil is now
being moved mechanically in a magnetic field it becomes a generator,
so the lower the load that it sees - in this case the output impedence
of the amp plus cable resistance - the quicker the energy will be
dissipated. As an amp output impedence is typically around 0.1R (or
less sometimes) then the resistance of a thinner cable can become
significant, hence why thick is better.


I don't see that. In addition to the output stage of amp and cable the same
current is *also* flowing through the speaker coil itself, they are all in
series. Therefore it is in the speaker coil where most of the energy is
dissipated, assuming that the output impedance of the amp is, indeed, low.
And also assuming that the cable resistance is low compared to the speaker
impedance. It follows that the cable resistance should be low compared to
the *speaker* impedance because it is this that has the major effect on the
overall output circuit energy dissipation and hence damping factor.

I see the setup as being analogous to a generator with a short circuit on
the output terminals, or a very low resistance load. The windings of the
generator heat up and dissipate more energy than the load.

But I do agree that thick cable is better :-)

Congratulations, you understand pretty much everything you need to
know, and you hit the nail on the head regarding 'damping factor'.
It's about power dissipation - and FR imbalances because the speaker
is designed to be driven from a low impedance.

--

Stewart Pinkerton | Music is Art - Audio is Engineering

On Mon, 6 Mar 2006 18:35:02 +0000 (UTC), "Jo"
wrote:

I'm aware of the never ending discussion on interconnects and speaker
cables, but I just want some advice on what to actually buy. Nominal
impedance of speakers is 6 ohms. Room is quite large and so amp/speaker
distance will be 4-5 meters. Speakers are bi-wired.

I just need an idea of cross-sectional area and where I can get some
suitable cable. I'm not convinced by the talk of OFC and so on.
Multistranded copper of sufficient thickness is fine by me. Suggestions
please ?

You should be aware that *all* multistrand cable is OFHCC (oxygen-free
high conductivity copper), because this confers the required
flexibility. Hence, OFC or OFHCC is jusyt a marketing label applied to
standard flexible copper cable. SAs to the rest, something like QED
72-strand or 105 strand will be more than adequate for your
requirement, and you can probably find the equivalent speaker wire
even cheaper at B&Q. Basically, aim for something like 12-14AWG
thickness if you can get hold of it.

BTW, bi-wiring does nothing whatever, so you're better running a
single run of thick cable and leaving the jumpers in place. If any
shop guy tells you that bi-wiring halves the cable resistance, ask him
what he thinks the crossover does, and check the blank expression on
his ignorant mug. Then buy somewhere else......
--

Stewart Pinkerton | Music is Art - Audio is Engineering

In article , Jo
wrote:


Thanks, I know about damping factor and the need to keep cable
resistance well below actual speaker impedance across the audio range.
I did some rough calcs and came up with a figure of 3-4 sq mm and was
curious about what the experts here suggested.

http://www.st-and.demon.co.uk/AudioM.../lscables.html

:-)

Slainte,

Jim

--
Electronics http://www.st-and.ac.uk/~www_pa/Scot...o/electron.htm
Audio Misc http://www.st-and.demon.co.uk/AudioMisc/index.html
Armstrong Audio http://www.st-and.demon.co.uk/Audio/armstrong.html
Barbirolli Soc. http://www.st-and.demon.co.uk/JBSoc/JBSoc.html

In article , Jo
wrote:
In , harrogate2
typed:

It is nothing to do with the speaker load impedence, rather the amp
output impedence.

When the loudspeaker cone is extended by signal, if the signal is
removed then it is down to the mechanics of the cone mount to return
it to its rest position - except that it won't, it will follow a
decaying oscillation path. During this time, as the voicecoil is now
being moved mechanically in a magnetic field it becomes a generator,
so the lower the load that it sees - in this case the output impedence
of the amp plus cable resistance - the quicker the energy will be
dissipated. As an amp output impedence is typically around 0.1R (or
less sometimes) then the resistance of a thinner cable can become
significant, hence why thick is better.


I don't see that. In addition to the output stage of amp and cable the
same current is *also* flowing through the speaker coil itself, they
are all in series. Therefore it is in the speaker coil where most of
the energy is dissipated, assuming that the output impedance of the amp
is, indeed, low.

That is correct. The problem with 'cable impedances' for speakers isn't
really due to need for 'damping' the mechanical resonance of the driver,
for the reason you explain. The electrical losses tend to be dominated by
the actual speaker resistance.

The problem is that most loudspeakers have an impedance that varies with
frequency. The amp+cable impedances then act with the speaker impedance to
make a frequency-dependent attenuator, and may alter the frequency response
- usually by a slight amount.

Slainte,

Jim

--
Electronics http://www.st-and.ac.uk/~www_pa/Scot...o/electron.htm
Audio Misc http://www.st-and.demon.co.uk/AudioMisc/index.html
Armstrong Audio http://www.st-and.demon.co.uk/Audio/armstrong.html
Barbirolli Soc. http://www.st-and.demon.co.uk/JBSoc/JBSoc.html

In article ,
Owain wrote:
Jo wrote:
I just need an idea of cross-sectional area and where I can get some
suitable cable. I'm not convinced by the talk of OFC and so on.
Multistranded copper of sufficient thickness is fine by me.
Suggestions please ?

6A or 13A mains flex. Available on 100m reels from electrical factors.

You'd have problems finding these in 2 core.

--
*Money isn't everything, but it sure keeps the kids in touch *

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

Hi,

"Dave Plowman (News)" wrote in message
...
In article ,
Owain wrote:
Jo wrote:
I just need an idea of cross-sectional area and where I can get
some
suitable cable. I'm not convinced by the talk of OFC and so on.
Multistranded copper of sufficient thickness is fine by me.
Suggestions please ?

6A or 13A mains flex. Available on 100m reels from electrical
factors.

You'd have problems finding these in 2 core.

You can sometimes find two core 3182Y in sizes up to 2.5mm, but I
don't know if it's available any larger than that. Most of the larger
sizes are three core. It's also a bit bulkier than the equivalent size
of 'speaker cable', due to the extra layer of sheathing.

Regards,

Glenn.

In ,
Stewart Pinkerton typed:
On Mon, 6 Mar 2006 18:35:02 +0000 (UTC), "Jo"
wrote:

I'm aware of the never ending discussion on interconnects and speaker
cables, but I just want some advice on what to actually buy. Nominal
impedance of speakers is 6 ohms. Room is quite large and so
amp/speaker distance will be 4-5 meters. Speakers are bi-wired.

I just need an idea of cross-sectional area and where I can get some
suitable cable. I'm not convinced by the talk of OFC and so on.
Multistranded copper of sufficient thickness is fine by me.
Suggestions please ?

You should be aware that *all* multistrand cable is OFHCC (oxygen-free
high conductivity copper), because this confers the required
flexibility. Hence, OFC or OFHCC is jusyt a marketing label applied to
standard flexible copper cable. SAs to the rest, something like QED
72-strand or 105 strand will be more than adequate for your
requirement, and you can probably find the equivalent speaker wire
even cheaper at B&Q. Basically, aim for something like 12-14AWG
thickness if you can get hold of it.

BTW, bi-wiring does nothing whatever, so you're better running a
single run of thick cable and leaving the jumpers in place. If any
shop guy tells you that bi-wiring halves the cable resistance, ask him
what he thinks the crossover does, and check the blank expression on
his ignorant mug. Then buy somewhere else......

Thanks for the info Stewart. I make 12 AWG to be about 3.3 sq mm, which fits
with my original rough calculation of (10 x Rcable)(Rspeaker) for about 5
meters length. I may add some temporary bi-wiring using some old single
strand power cable I have. Just out of curiosity :-)

Jo

"Jo" wrote


Thanks for the info Stewart. I make 12 AWG to be about 3.3 sq mm, which
fits with my original rough calculation of (10 x Rcable)(Rspeaker) for
about 5 meters length. I may add some temporary bi-wiring using some old
single strand power cable I have. Just out of curiosity :-)



Post your findings here when you have tried it.

(I have never noticed any difference with biwiring in the past....)

In ,
Jim Lesurf typed:
In article , Jo
wrote:


Thanks, I know about damping factor and the need to keep cable
resistance well below actual speaker impedance across the audio
range. I did some rough calcs and came up with a figure of 3-4 sq mm
and was curious about what the experts here suggested.

http://www.st-and.demon.co.uk/AudioM.../lscables.html

:-)


Hiya Jim, your site was where I got my original cable csa info from. Thanks
for putting those pages up :-)

Jo