one for the theorist

[Tom Priore]

	I've seen very in-depth analysis of wire especially the stranded vs. solid.
what I gathered was that with stranded the single propagates on the skin of
each strand diving in an out of the core of the wire. so when the wire is
attached at the other end the components of the signal could feasibly travel
different distances from each other and high frequencies could suffer
interference with itself.
	now back to the practical world... signals propagate down wire pretty
fast.. I think its like 1/10th the speed of light. the human ear can hear up
to about 40,000 Hz. for any real damaging interference the signal would have
to be around 45 degrees out of phase. The difference in path length for
components to achieve interference would have to be pretty big.

ok heres some math i hammer out real quick to show you what I mean.
assume a signal with f=40,000hz or 40,000 cycles / second
assume the signal propigates at 1/the speed of light:
.10*3E8=3E7 meters/ sec
to find out how many meters are in a cycle: (3E7 m/s)/(40,000 cycles/s)= 750
meters per Cycle.

That means for complete destructive interferance the DeltaL (the differenc
lenght) must be around 375m. For construtive the Length needs to be 750m.

Thats a pretty long wire for the strands to have that kinda length
difference.

Now consitter that there are allot of strands... ar real lot. Statisticly
each occurance of destructive interfearance should be cancled by
constructive interfearnce.

End result?
Stranded wire is good enough for my studio.


-----Original Message-----
From: owner-synth-diy at mailhost.bpa.nl
[mailto:owner-synth-diy at mailhost.bpa.nl]On Behalf Of J. Larry Hendry
Sent: Wednesday, July 14, 1999 9:24 AM
To: synth-diy at mailhost.bpa.nl
Subject: Re: one for the theorist


> From: pharding <pharding at mail.ndirect.co.uk>
> Is this anything to do with the "skin effect" theory? This is where
> it is believed that electrons tend to flow on the outside (skin) of a
> wire rather than straight down the centre,hence the theory of
> loudspeaker cables made from lots of small strands as opposed to a
> solid core.....

I always thought that skin effect was linited to "high" frequencies.
Someone care to comment above what frequency that becomes an issue?  As far
as speaker cables, I think stranded is just a practical application of
making the wire flexible.

Larry Hendry