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Tomorrow I venture into the crawlspace under my house to run speaker cable. There's no other practical way to run in-wall cable in my home. I've been thinking about how the length of the cables will vary over the course of the year as the temperature changes.


As a worst possible case, suppose that the temperature in my crawlspace varies by 55 celsius (100 Fahrenheit) from winter to summer. Using the thermal expansion coefficient for copper shows that my longest cable (7.6m or 25ft) could change in length by about 7mm (about 1/4 inch). Realistically, I expect the true temperature variation to be about half that, because the cable will be snug up against the floor boards.


To avoid different cables expanding and contracting by different lengths, I can make sure they are all the same length to start with. What other problems might arise from cables changing length? Has anyone else had experience with this? Does sound quality suffer?


What about cable temperature changes in general? Is condensation relevant? Will the outer cable casing hold up? I'm using in-wall cable, not outdoor cable (specifically monoprice 12 gauge 2 conductor in-wall cable ).


I hope you'll all tell me I'm wasting my time thinking about this and that you've run 1000's of meters of cable outside with no issues.
 

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You are wasting your time thinking about this, also having all the cables the same length is a myth perpetuated by expensive speaker cable salesman. One day I worked the math and a difference in speaker wire length of 20 ft results in a timing difference that is less than moving your ear the thickness of your ear drum.
 

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Quote:
Originally Posted by BIGmouthinDC  /t/1520368/speaker-cable-length-change-due-to-outdoor-temperature/0_40#post_24423720


You are wasting your time thinking about this, also having all the cables the same length is a myth perpetuated by expensive speaker cable salesman. One day I worked the math and a difference in speaker wire length of 20 ft results in a timing difference that is less than moving your ear the thickness of your ear drum.
I beg to differ! Here's why:

Consider speaker cable to have a Velocity of Propagation of .9; at 186,000 Miles per Second as the speed of light the signal travels about 10.6 Trillion Inches Per Second; ergo it takes 9.428212833230754e-11 Seconds for it to travel 1" OR 2.357053208307689e-11 seconds to travel the .25" the cable length will vary! WE'RE TALKING TRILLIONths OF A SECOND HERE!!!!!




If I were you I would highly consider adding environmental controls to that crawlspace. A couple thousand dollars spent on a heat-pump and insulation for that crawl will go a long way toward providing peace of mind...




Or do as most of the rest of us would and don't sweat it.
 

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You can't have your speaker cable change temperature along the run. If it goes from a warm equipment cabinet to cold crawl space, then back to the warm room, the temperature delta will cause inconsistent diffraction of the waveforms. The same thing happens in water filled caves.


You'll need to encase your speaker wires inside fluid filled tubing. Circulate the fluid to keep the temp within 0.025C along the full length of the run.
 

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Please stop guys - I'm cringing so much with the uber-sarcasm that my testicles have started to withdraw into my body...



However! Judging by his name and the amount of posts he's made since joining in 2008 (8), and the amount of thumbs up he's received in that time, I've a feeling he could be posting for laughs - I think I'll look at his previous posts and see what delights he's given us in the past!


Gary
 

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Quote:
Originally Posted by thrillcat  /t/1520368/speaker-cable-length-change-due-to-outdoor-temperature#post_24424951


Who's going to play Sheldon in the pilot of "The Big Theater Theory"?

I think Big kinda did that one, though in more of a gruff manly voice



Gary
 

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Quote:
Originally Posted by Gary Lightfoot  /t/1520368/speaker-cable-length-change-due-to-outdoor-temperature#post_24425498



However! Judging by his name and the amount of posts he's made since joining in 2008 (8), and the amount of thumbs up he's received in that time, I've a feeling he could be posting for laughs - I think I'll look at his previous posts and see what delights he's given us in the past!


Gary

Hmmmm, I take it back..
 
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