using house electrical wire.

What is the advantage and disadvantage of using wires that you use for home electrical in car audio. If using the same thickness.
Eg. If using 8 guage audio power wire vs an equivalent electrical wire of same current carying capacity to power amps. Same with the speaker wire of using lets say 4mm to 10 guage.
I know that one disadvantage is that electrical wire is much stiff and less flexible.

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"I'm So Loud It Hertz"

That's the only disadvantage. Car wire is generally designed to be more flexible, so as to not fail from vibrations as soon.

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It all reminds me of something that Molière once said to Guy de Maupassant at a café in Vienna: "That's nice. You should write it down."

slab42 wrote:

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A few other differences are:

Most car wiring is designed to resist oil/gas/heat, etc. whereas most home wiring is not.

Home power wiring is generally solid wire, because AC current in your house travels at roughly 60hz(not sure of the exact frequency, but it is near there), and low frequencies travel better through solid wire vs stranded wire.  Car power wiring is multi-stranded, because the DC current in your car travels better on the stranded wire.  This is one reason why the flexibility you speak of is so different.

HTH

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Most home wiring is THHN or THHW rated insulation, which are high temp, (or heat) chemical resistant (oil and gasoline) thermoplastics, and in the case of the THHW insulation, it is UV resistant as well, so it can be used in "weathered" spaces. While neither of these are ideal for car use, as they are stiffer than the insulations used for "car wiring", there is no difference in the wire itself. Additionally, very little home wiring is solid over about 12 or maybe 14G. While you CAN find it, those wire gauges, when solid, are too hard to pull. Romex WILL be solid, but it's not pulled through conduit (in fact, it's against the NEC to install it in conduit) rather it's stapled to structural members in it's run.

While you do bring up a valid point in the reference to "skin effect" (whih is what you are referring to when you say 60Hz "travels better") skin effect has ZERO effect at 60Hz, and even less effect at DC. (There is no skin effect at DC) Skin depth at 60Hz is .386 inches. This means that a wire would have to be .782 inches in diameter for the DC resistance to equal the AC resistance at 60Hz. Until you reach around 3K or so, the gauge of the wire will have little to nothing to do with the AC resistance of the wire.

For DC purposes, you can use ANY wire, "car-" or "home-" rated, as long as you know that the stiffer wire and insulation MAY fail sooner than the not-so-stiff stuff. Electrically, they are ABSOLUTELY no different, at DC.

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It all reminds me of something that Molière once said to Guy de Maupassant at a café in Vienna: "That's nice. You should write it down."

Thanks for the info..

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"I'm So Loud It Hertz"

haemphyst, you have a way with words. Not many people can express complexity with style and ease. Certainly an art. Bravo!

audiocableguy wrote:

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haemphyst, you have a way with words. Not many people can express complexity with style and ease. Certainly an art. Bravo!

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Thank you...

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It all reminds me of something that Molière once said to Guy de Maupassant at a café in Vienna: "That's nice. You should write it down."

slab42 wrote:

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me power wiring is generally solid wire, because AC current in your house travels at roughly 60hz(not sure of the exact frequency, but it is near there), and low frequencies travel better through solid wire vs stranded wire.

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Um...no.

You have the right idea, but your numbers are completely wrong. You're off by about a million. Literally.

Skin effect doesn't come into play until the frequency of interest reaches (roughly) the MHz region. At 60Hz (the line frequency in the US), the skin effect is so tiny, it's effectively zero. We're talking lots of zeros to the right of the decimal point here.

The reason that solid wire is used in homes is because it's cheaper to make and easier to work with. That's all.

Sorry to nitpick, but this is one that gets me riled up every time.

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This is not a sig. This is a duck. Quack.

Not that many zeros...

Actually, EVERY AC current will exhibit skin effect, and have a depth involved with it. Even as low as 1 cycle! The lower the frequency, the deeper the skin depth. When the conductor diameter EQUALS twice the skin depth, the DC resistance, and the AC resistance are equal. Smaller than 2X skin depth, and the AC resistance will be HIGHER than the DC resistance. When designing tesla coils, we try to make our secondary's wire gauge as small as possible, (it's less expensive that way, and as the secondary is low current, a lot of copper isn't necessary...) but we base that wire gauge on the frequency of the secondary - AWG (or diameter) = 2X skin depth. Larger than 2X is more wire than you need, (as no current travels in the center of the conductor) therefore wasteful, and offers no performance advantage. Smaller than 2X, and your AC resistance increases and reduces the efficiency of the tank circuit... i.e. shorter sparks.

Now, the primary is a different story, but the same. In the primary, we use copper tube, and generally speaking, it can be very thin walled copper tube. The primary is a very high CURRENT section, but because the ringing is still very high frequency, it still exhibits a very shallow skin depth. The current requirements need lots of conductor, still, so, a tube fits the bill very nicely, without using more copper (UNUSED copper, I might add) than necessary.

As I said above, the skin depth at 60Hz is .386 inches. Over 1/3 of an inch! My math, using the following formula, comes up with .98cm. For copper at 100 deg. C, the skin depth is calculated by:

Skin_Depth in cm = 7.6/SQRT(Frequency) where, Frequency is in [Hz]

At 60Hz, stranded or solid will present VERY little difference, as the individual conductors are not insulated from each other in the case of stranded - at 60Hz, it's effectively a solid conductor. The reason for the stranding, is for no other reason than flexibility - it pulls easier. Trust me on this one... I'm a trained electrician, and I've pulled more wire in my life, than you've probably DRIVEN in yours! OK, slight exaggeration there, but you get the idea... miles and miles!

So all I'm really saying is that every AC current will have a skin depth, and the lower the frequency, the deeper that skin depth is, but at lower frequencies, the difference between stranded and solid is nothing.

And don't get me started on Litz wire!

Here's a link for more litz info! (Just in case anyone is interested...)

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It all reminds me of something that Molière once said to Guy de Maupassant at a café in Vienna: "That's nice. You should write it down."

haemphyst wrote:

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Not that many zeros...

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Yes, skin effect depth goes as 7.6/sqrt(f), precisely as your equation shows. What you didn't account for is that the actual effect of skin effect doesn't start to matter in terms of loss or signal distortion until the skin depth is <1% of the wire diameter (for low voltage (<1kV)). Skin depth in excess of the wire diameter is no big deal.

For a 10AWG solid house wire with a diameter of 0.1019", that means that the skin must be 0.001", which gives a critical frequency of roughly 9MHz or so.

60Hz<<<<<<9MHz. 0.00066% to be exact. That's plenty of zeros for me.

For microwave frequencies or high power broadcast work, yeah, skin effect has a real contribution (the output for most 50kW broadcast exciters is basically a 4" diameter piece of copper pipe), but for things in the audio frequency (<50kHz) it's effectively zero.

Don't get me started on Litz or other esoterica either. I spent years debunking a lot of the stuff that surrounds those "technologies".

You've pulled more wire, I'm sure, and I'm not trying to be a dick, but I got my degrees in this stuff, and I do things like design RF systems for a living. The math doesn't lie.


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This is not a sig. This is a duck. Quack.

WHOA... dude... calm down.

I see now what you were trying to say. I simply misread what you typed the first time... I took it the other direction, that's all...

I see what you are saying, and I don't disagree, but wow... I guess it DOES get you riled up.

All I was trying to say to the OP, and slab42 was that at DC there won't be any difference between a "home" wire, and a "car" wire, electrically speaking, but that home MIGHT be more brittle in the short-term, in the vibration prone environment of a car. The insulation ISN'T a factor, in this case, as most of the wire for the home will FAR outperform "car" stuff anyday, both thermally and chemically, and as long as the appropriate gauge is selected, there will be no difference.

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It all reminds me of something that Molière once said to Guy de Maupassant at a café in Vienna: "That's nice. You should write it down."

We're cool as ice dude, it's all good.

Yeah,..I do get a little worked up about technical stuff sometimes. You should try digging up some of my old RC car tech forum posts on wire size and connector loss. I nitpick the technical detaisl, and it get me in trouble from time to time. I tried to make the post appear friendly, but I obviously missed the mark. Mea culpa.

We definitely took it in different directions. Yes, the OP can use house wire. It'll be a pain in the butt to install, and probably won't last as long due to brittleness issues, but our conclusions were the same. I actually do have a little bit of some really beefy 1/0 panel wire in my car as a ground, but it's due to get swapped out the next time I tear my trunk apart. It's only in there because it was the handy bit of the right size wire when I was rushing to get the system installed...I'd never choose to use it on purpose, only because it's stiff as hell and a b*tch to crimp a connector onto. Thankfully it's only a foot and a half long, and doesn't ever need to flex.

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This is not a sig. This is a duck. Quack.

Epilogue

Hey kids out there in car audio internetland:

I suspect your Dad might have a roll of 14/2 household electrical wire in the basement... but keep it out of your car.

Please.

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Build the box so that it performs well in the worst case scenario and, in return, it will reward you at all times.