Copper cable and skin depth

[Fantastic]

I mentioned long ago about skin depth and gave some figures.
Capt. Rajesh asked for details about thicker wire which I did not have that time and as usual , as the thread gets older it gets lost !
I lost the link to the original web page but accidentally came across another one today which mentions all wire sizes. You can take your pick !

American Wire Gauge table and AWG Electrical Current Load Limits with skin depth frequencies and wire breaking strength

It would be interesting ( an inexpensive !) to experiment with thinner enamelled wire in groups ( each less than 1mm dia) as speaker wire.
Possibly use less than 1mm max dia for woofer/mid and maybe 0.5 mm dia for the tweeters. Calculate the no of wires needed to use in parallel to achieve the resistance you want.

For example to get 4 square mm ( about AWG 11) you can use 8 wires of 20 guage (SWG) in parallel. These will be insulated from each other and so 'possibly' is better than a bunch of smaller wires uninsulated from each other. Rather like Litz wire but on a bigger scale !
Maybe same could be done for the tweeter wires too with even thinner wire.
Bundle them separately ( + and - leads) in teflon tubing and put the two resulting cables in a braided nylon tube ( available ) with heat shrink tubing at the ends and voila you have a $1000+ cable !

Anyone interested in trying it out ?

By the way I had also mentioned about using single core silver plated copper wire with teflon coating as a line level interconnect. I bought some 30 SWG wire ( 0.32mm) and used 3 wires per cable twisted about 3 or 4 times per inch. Decent RCA plugs at the ends.
How did it sound ? Like a very nice cable ! Nothing lost. Good HF and good all the way through ! But it does pick up hum even though the third wire is earthed at one end. But I must admit the situation was not ideal. There were a couple of open ( powered up ) transformers fairly nearby. But then again the hum was very low and only audible when you put your ear near the speakers. It's very nice ,so I continue to use it in place of the original cable. No time to do exhaustive tests but it was money well spent !
Total cost : 4 RCA's 400/- 1.5 meter cable x6 lengths at 9mx6/- = 54/- = Rs454/- + labour plus transport !
That works out to about a minimum of least Rs 2500/- !!
Suggest you try it out .

 

[captrajesh]

It would be interesting ( an inexpensive !) to experiment with thinner enamelled wire in groups ( each less than 1mm dia) as speaker wire.

Possibly use less than 1mm max dia for woofer/mid and maybe 0.5 mm dia for the tweeters. Calculate the no of wires needed to use in parallel to achieve the resistance you want.

Thanks for sharing the link.

Yes I did read about skin effect. Infact the idea struck me long time back; to insulate individual strands of wire and braid them for minimising skin effect and maximising the conducting surface. When I discussed this with a knowledgeable FM, he said that the capacitance would increase exponentially.

 

[IndianEars]

Fantastic... thanks for the link. Its informative.

I have a couple of thoughts :

1. Maybe you can wrap your DIY cable in Kitchen Al Foil as the shield, which ideally should be grounded at one end.

2. Yes, CaptRajesh.... Bundling multiple strands will increase the resultant capacitance. Also, thinner cores will exhibit Higher Skin Effect.

Often a recommended solution is to use a bunch of Different dia wires, each insulated, to give the best performance over the audio freq band.

Also, High prices audiophile cables use High purity conductors ( Cu or Silver etc). The cost of such conductors goes up Exponentially with purity.... There are sellers on eBay.com

 

[Fantastic]

IndianEars, Yes the Al foil did occur to me too. But here again we will be introducing capacitance to ground. If the hum is non intrusive I'd leave it as it is. For me it is currently not an issue at all as I can't hear it from the listening position .

Someone has tried using multiple strand enameled wire for speakers. I read about it a long time ago but don't seem to recall anything about the test results ! I'll try it sometime soon. I have enameled wire of the right dimension. The problem however is 'time' ! I'll also have to probably stick to silicon coated fiber external insulation as it's easier to get . PVC tubes are also available but generally not well recommended. Maybe the plus and minus cables ( forward and return) can be loosely put together with shrink tube at intervals.

What did you mean by " thinner cores will exhibit Higher Skin Effect ". The statement isn't clear . If you mean that the wire becomes a poorer conductor at smaller diameters , I think it isn't correct.
If this was true then Litz wire should not do what it does. Skin depth is frequency based. So as you reduce the wire diameter the percentage of the core of the wire used for current flow ( at the same frequency) will increase.
That's why they use a bunch of insulated fine wires to make a Litz wire.

Never mind the details. It will be interesting to try it out. I did try regular multistrand non insulated speaker wire against thin single core wires. The single core did sound brighter on the tweeter ( bi wired).

 

[IndianEars]

Fantastic,
Skin Effect IS dependent on the Radius Of Curvature of the Current carrying conductor.

Sharper curvatures cause Greater "Current Crowding" ie higher current density where curvature is higher..... Particularly where the radius of curvature approaches the Skin depth.

 

[omishra]

Guys, if you want each small wire insulated then why not shorting all wires at the ends of CAT6 wire? They are 8 wires individually insulated and 99.9% OFC. Form factor is convenient and less capacitance.

I am already using it as speaker cable into my TV setup. I find its good cable.

AudioKarma.org Home Audio Stereo Discussion Forums - View Single Post - Even more DIY speaker cables

http://www.hifivision.com/diy/47693-made-speaker-cables-out-lan-cable.html

 

[keith_correa]

CATn solid strands are 24 AWG which use 100% of the conductor at 20 kHz. Just use as many insulated strands as needed and twist them like LITZ wire. That's all you need for theoretically correct speaker cables that'll take care of the skin effect. Of course, if you do the twisting by hand, be prepared to get blistered fingers. If you have a variable speed drill, you can rig up an easy jig to use with the drill at low speeds and twist the strands nicely and uniformly.

 

[Fantastic]

Many people have been using Cat5 cables as speaker wires. Lots of information on the results on the Net. It wasn't always 'great'. But then it depends on who's reviewing it. Better to try it in ones own system as it isn't very expensive.

I did use it once but didn't like it compared to the cable I had at that time. However the speakers are different now.

 

[IndianEars]

I agree with Fantastic. I tried Belden Teflon Cable and was not happy with the results. The sound to me, in my system was lean and somewhat hard. Lacked both .. ambience and decay.

However these are a Good alternate to generic cables.

 

[keith_correa]

Duplicate post; deleted.

Tch! Tch! Tch! Back to back posting?

Sorry Rajesh, that is petty of me, but I just couldn't resist that.

 

[quad]

Since we are talking of skin depth (jury is out on it's applicability
at audio frequencies - depending on who you talk to),
it is probably relevant that as per various audio forum posts, tubing
made of teflon (as suggested by the OP) can suffer from triboelectric effects.
Just another thing to bear in mind

 

[keith_correa]

If using CATn cables, a lot depends on the geometry employed. Often, sub-optimal geometry is used resulting in high inductance and then people diss CATn. But, that's material for its own thread.

 

[keith_correa]

Since we are talking of skin depth (jury is out on it's applicability at audio frequencies - depending on who you talk to),

Oh, it is applicable all right. Whether it is audible or not is another story.

it is probably relevant that as per various audio forum posts, tubing
made of teflon (as suggested by the OP) can suffer from triboelectric effects.
Just another thing to bear in mind

Correct! No such thing as a free lunch.

 

[captrajesh]

Bundling multiple strands will increase the resultant capacitance.

I understand that. How about braiding?

thinner cores will exhibit Higher Skin Effect.

Are you sure? From what I read somewhere on the net, I gathered that the opposite is true.

 

[mbhangui]

Not to do with skin effect. More to do with test done by passlabs on different cables

https://passlabs.com/articles/speaker-cables-science-or-snake-oil

 

[magma]

this article is accurate except for the resistance , inductance and capacitance
figures

of a couple cables

all models used in THAT test are OLD

the newer cables have completely different figures

im glad someone highlighted this article
If you read it fully
One realizes the whole cable "thing" is NOT really snake oil even according to Nelson

different values and different cables DO offer something differnt
(at least thats my personal take on the article - others will interpret it how they will )

 

[keith_correa]

NP says:

If, like many audiophiles, you have spent a small (or large) fortune on your hi-fi system, money spent for high quality cables and connectors is a reasonable investment.

So, for folks who like me use "ghetto" equipment, this "reasonable" investment on wire becomes extremely unreasonable

 

[omishra]

In my modest diy setup, investment in mogami interconnect and speaker wires brought difference which could be noticed.
When i upgraded to better interconnect, listened difference in HF and tonal quality of vocal improved. With speaker cable upgrade same experience repeated but this time felt loudness too increased.

 

[Fantastic]

I think we should be clear about what we are observing. All amplifiers , power amps and preamps, reacts differently to loads that are not 'pure resistances'. A practical cable has resistance, inductance and capacitance . This varies with the way the cables are made . So we now have different impedances in series with the amp and the actual load which is also NOT a pure resistance .

So without even going into details we can see that the end result will vary with different cables. Some having more variance than others. It's not about being 'more accurate' but more about 'which effect' we like more !
The most accurate ( not altering the original signal) would be the shortest cable you can use. Possibly less than a foot !

I might guess that having a choice between a long speaker cable and a long preamp cable (XLR...balanced) where the power amp is right next to the speaker, the long preamp cable would be a better bet at 'not modifying the original signal significantly ' . Cheaper too !