Running together coax and speaker cables...

[Faustino Dina]

Hi,

I need to run coax (audio-video signal) cables together with two twin
speaker cables between two rooms.
Will the signal (specially speaker cables that are not shielded) be degraded
because of the interference between the cables?
How far should I run coax cables from the speaker cable?
How far should I run one pair speaker cable from the other pair?

Thanks in advance
Faustino

[Kevin McMurtrie]

In article >,
"Faustino Dina" > wrote:

>Hi,
>
>I need to run coax (audio-video signal) cables together with two twin
>speaker cables between two rooms.
>Will the signal (specially speaker cables that are not shielded) be degraded
>because of the interference between the cables?
>How far should I run coax cables from the speaker cable?
>How far should I run one pair speaker cable from the other pair?
>
>Thanks in advance
>Faustino
>
>

It's no problem. Unless you've done something crazy to the cables, like
separating the wires, the magnetic fields will cancel well enough that
you won't get mixing.

[Faustino Dina]

Ok, thanks all, I'll sleep well tonite... ;-)

[Jim Lesurf]

In article >, Arny Krueger
> wrote:
> "Kevin McMurtrie" > wrote in message
>

My apologies for the following burst of academic nit-picking. However since
this is being cross-posed to a 'tech' group I suddenly felt the urge...
;-)

> > It's no problem. Unless you've done something crazy to the cables,
> > like separating the wires, the magnetic fields will cancel well enough
> > that you won't get mixing.

> Exactly.

> Speakers are typically floating loads.

Yes. Although with most domestic audio, the signal connection from the
power amp to the speaker is *not* balanced. Hence the E-fields near the
cables (assuming a form of twin-feed) are non-zero. Hence capacitive
coupling to nearby objects may well occur. This probably does not matter in
most cases, though. :-)

> This means that the magnetic fields around speaker cables due to signals
> flowing through the cables are symmetric and cancel quite nicely.

In the 'far field' <sic>, yes. However closer in, the fields are the
superposition of those of the outward and return conductor bundles which
normally do not cancel to zero. (Otherwise the field everywhere would be
zero, the Poynting vector would be zero, and no power would flow!) Hence
some H-field coupling may occur to nearby conductors. As above, this
probably does not matter in most cases, though. :-)

> If you want to get as much of this cancellation effect as is reasonably
> possible, twist the speaker leads. A power drill or power screwdriver is
> a good tool, but don't go overboard by twisting them tightly to the
> point that they are damaged. Twisting will slightly shorten the speaker
> cable's length.

Twisting will probably reduce any overall H-field couping. However it may
have less effect on E-field coupling. I'd agree it is a good idea, though.

Slainte,

Jim

--
Electronics http://www.st-and.ac.uk/~www_pa/Scots_Guide/intro/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

[Richard Crowley]

"Faustino Dina" wrote ...
> What means "balanced"?

It means "symmetrical", "push-pull", "differential", etc. where a pair of
wires carries the signal in opposite polarities. Any outside interference
will affect both wires equally, and the receiving circuit ( microphone
preamp, speaker, etc.) will cancel the "common-mode" noise.

> I read somewhere that "balanced"
> (cables) are beter than unbalanced ones,

In many cases. But there are tradeoffs, so it is not universal.

> but I suppose the amplifier should output "balanced" signal....???

The vast majority of power amps (particularly those without output
transformers) have one side of the output grounded.

However, in most cases the wiring to the speaker, and the speaker itself are
completely "floating" (i.e. not connected to anything else). This provides
as much of a "balanced" circuit as you need for intereference-resistant
speaker wiring.