Why are speaker wires "frayed"

Solid wire is very stiff and inflexible. So it's purely a "handling" issue.

--Ethan

Flexibility is the main reason to use stranded wire over a single thicker wire. There is no reason not to use a solid core wire, I do on 2 of my speaker setups (Romex 2 conductor 14ga wire).

Drew

solid wire will snap once and poof* gone.... you need a new one again lol

stranded wire got a lot to snap... so if one snap, 34 more wire to go (woots!)

yeap... it's a lil about durability

I'll take "skin effect" for $600 Alex.

Alternating currents tend to want to travel near the surface of the conductor.  Many small conductors have more surface to volume ratio than one large conductor, so there is lower resistance to AC  in stranded cable than solid.

It matters more in higher frequency stuff, probably not very relevant at audio frequencies, but --- as always --- there's plenty of controversy.

Quote:

Originally Posted by Tyll Hertsens 

I'll take "skin effect" for $600 Alex.

 

Alternating currents tend to want to travel near the surface of the conductor.  Many small conductors have more surface to volume ratio than one large conductor, so there is lower resistance to AC  in stranded cable than solid.

 

It matters more in higher frequency stuff, probably not very relevant at audio frequencies, but --- as always --- there's plenty of controversy.

Stranded wire really won't do anything to ameliorate skin effect nor does surface area have anything to do with it, all else being equal.

Litz wire won't help either unless it's of the Type 2 variety.

Type 1 litz wire is like your typical stranded wire, i.e. the wires are all twisted together in a single twist, except the individual strands are insulated.

With this type of litz, the individual strands tend to remain at the same radial distance from the center throughout the length of the wire. Because of this, the current densities will be greater in the outermost wires just as current density is greater in the outermost portions of an equivalent solid  core wire.

Type 2 litz takes a number of wires, twists them together, and then subsequently twists multiple bundles of those together in what's often called a "rope lay."

The result is that on average, each individual wire occupies all of the radial positions from the center to the outermost portion of the wire along the length of the wire and consequently, each wire has the same current density as all the other wires.

So, if the wire's uninsulated stranded wire, its only real purpose is flexibility and reliability.

se

1. solid is hard.. 

2. stranded are flexible..

3. skin effect..

4. solid wire cost much..

5. why look for solid if we have stranded one.

Actually, bare stranded does nothing to help with regard to skin effect (provided it's something that even needs to be worried about in the fist place).

And all else being equal, stranded costs more than solid as it requires more wires which have to be drawn down to smaller diameters and then twisted together.

But yes, stranded is more flexible which is its primary advantage.

se

Quote:

Originally Posted by nick_charles 


An interesting article with models and measurements on the relevance of skin effect for loudspeaker cables

Thanks, Nick. Familiar with that one.

Also, Jim Lesurf of Scots Guide wrote a similar piece:

http://www.st-andrews.ac.uk/~www_pa/Scots_Guide/audio/skineffect/page1.html

se

Quote:

Originally Posted by Steve Eddy 

Thanks, Nick. Familiar with that one.

 

Also, Jim Lesurf of Scots Guide wrote a similar piece:

 

http://www.st-andrews.ac.uk/~www_pa/Scots_Guide/audio/skineffect/page1.html

 

se

 

 

Seen that one myself - we need a bibliography of decent articles as befits this subforum.

Quote:

Originally Posted by nick_charles 

Seen that one myself - we need a bibliography of decent articles as befits this subforum.

Good idea. This forum could use a sticky.

se

some direct measurements:

http://www.passlabs.com/pdfs/articles/spkrcabl.pdf

extreme lengths (movie theater speaker cabling)

http://www.hps4000.com/pages/spksamps/speaker_wire.pdf

in the DiyAudio “skin game” thread I did a few sims that show that “proximity effect” is actually larger: http://www.diyaudio.com/forums/everything-else/21348-skin-game-6.html#post249812

“of course armed with little knowledge and free software you could just simulate:

2mm dia Cu conductors, 4mm cntrs, 1 A @20KHz

re 50 Hz values of 0.0119 Ohm R and 0.667 uH ( /m)
”

an increased resolution, view of just one (half) of the pair exploiting symmetry for higher effective grid resolution:

the John Allen article claims stranded wire gives measurable excess loss at high frequencies – I believe the proximity effect viewpoint is useful in explaining it – the current “wants” to crowd towards the opposing current stream, if the internal strands spiral then there is some emf pushing the current to move from strand to strand at opposite the pitch rate – which involves the higher inter-strand contact resistance

I would still caution to employ high skeptism when encountering audiophile cable commetary with terms like "microdiodes" and "strand jumping"