If speaker wires are run through your attic or crawl space under the house is the signal affected by the ambient temp of the wire. In the summer it could be 120 deg. in the attic or
35 deg in the crawl space. Could you have a condensation problem inside the wire on very humid cool days. Does a signal current warm the wire at all, so when there is no signal after system is turned off at night is the creation of condesation possible?
I realize house electrical wiring runs through the same areas and have never heard of this being a problem but I guess you would have to check the quality of the electrical signal not just voltage or amps. Could you even have the right voltage and amps and have a poor quality AC signal?
I'm just curious about this as I am about to run new wires for surround speakers.
Not losing sleep over this just curious.

Brad

i can answer one question:current will warm a wire.way back when...using cheesy speaker wire i melted the insulation,wires shorted,amp fried.

if you use 14-12 gauge wire you will most likely be fine.

i read a study of how temp. changes will alter a speakers performance but haven't heard anything about wire.

Metal's conductivity is dependent on temperature, but not enough so for such small variations as a 100 degree range. We had a large (and largely sarcastic) debate a year or two ago about condctivity of different materials, and I had some old reference books at my desk at work with conductivity values that I referred to at the time - they probably gave some guidance on conductivity in relation to temperature, if you are interested.

Power wiring can be warmed by the current, but if the wire is sized per code the heat generation should not be significant (especially at the 120V level used in homes). This is actually why you often hear warnings about aluminum wiring in homes - its lower conductance causes it to heat up more, making it easier to overload a circuit enough to create a fire hazard if you aren't careful. Speaker wire should experience less heat gain from current than power wiring, especially if you use a good gauge of wire (14ga or 12ga should handle most any typical home theater speaker load you're likely to have, doubly so for surrounds).

You mentioned condensation, but I will behave myself and leave the psychrometric chart in the drawer. Let's just say that heating a surface will push you away from the dewpoint and make condensation less likely. We worry about condensation on cold surfaces - hot surfaces are safe.

In all my years in recording studios, and in over-the-top higher end home audio/theater settings, I don't think I've ever been in a situation where a speaker wire was made even warm to the touch. Unless you're trying to push many hundreds or thousands of watts at rather high amperage to a speaker, I find it pretty hard to believe that you could melt even cheesy zip cord with an audio amp.

I agree with Gonk that even at double that temperature range it probably makes an insignificant difference in the conductivity of the wire. Nothing to worry about.

Cheers,

Gonk, What,is a psycrometric chart? I still have to scratch my head at night in bed when the weather person talks about the dew point.

Brad

Sorry, the HVAC engineer in me spilled out for a moment. A psychrometric chart is a chart that tracks the moisture capacity of air at different temperatures. It's rather odd looking (think of a square but with the left corner cut off in a curve) - lines rising straight from the bottom are dry bulb temperature (the temp you read with a thermometer), lines running diagonally from top left to bottom right are wet bulb temperature, curves running from bottom left to top right are relative humidity curves. The point where wet bulb and dry bulb intercept is the dew point. Toss in a few more lines, and you get a really confusing mess. On the bright side, it is possible to tell a lot about the temperature, moisture content, and changes that take place to both if you are familiar with it.

The reason that it all works is that a pound of air can hold a specific amount of water, but that specific maximum changes a lot as you change the temperature of that air. If you dump a spoonful of water into a pound of 70F air, it should be able to hold all of it and have room for more, but if you cool that air to 50F the maximum moisture content changes and the spoonful no longer fits. When that happens, some of the water falls out - that's condensation. Dew point is the point at which the air cools to the point where it is completely full of water, such that cooling it any more will cause water to start falling out. Relative humidity is a measure of how full the air is - 40% RH means the air is holding 40% of its maximum capacity.

ritz,believe me,it happenned!now that i'm older i can say it was 'maybe' 18 gauge wire.amps were:crown 150a(2 bridged mono).i remember,like yesterday(it was almost 20 years ago!)

btw:they were powering akai 12"2 ways with tweeters disconnected.

btw2:here's the gut's of my new project:
http://www.msnusers.com/stereoandtruckphotos/shoebox.msnw?action=ShowPhoto&PhotoID=87

toad,

Heh, I didn't mean to imply that I didn't believe you...only that it is a bizarre thing that I've never seen. Perhaps there was some other issue at work. It takes quite a bit of energy to get 18AWG zipwire to glow hot enough to melt the jacket.

I've been to a home where the owner had a pair of 1200 watt VTL tube monoblocks and his overpriced MIT Oracle speaker cable was on back-order. I arrived to hear the amps playing at extremely loud levels into some big Dunlavy speakers over light gauge Home Depot speaker cable. He'd been playing with them for hours and I was a bit concerned about the cable so I had him crank it up while I held my hand around a section of the cable. I couldn't detect any heat. But being the paranoid sort, I drove home and dug up some 10AWG cables I had in my "extra stuff" drawer. To be honest, neither of us could really hear a difference in the sound quality after the "upgrade." Go figure.

Cheers,

Cheers,

Thank you Dr.Gonk,(Bill Nye the science Guy has nothing on you). That was a great explanation of the dew point. First time I have understood it.
I have to run about 50'of wire to the 4 ohm surrounds so I guess if I'll find a good deal on #12 of some kind and use that.

Thanks all

Brad