Not your typical speaker wire question
 

What's the tensile strength of one side of 18-gauge speaker wire?

Don't ask why... it's a temporary solution to a current problem.

Thanks!

Copper strand wire can hold about 20 pounds if I'm remembering correctly, but it really depends on the application.

And yes, we want to know why.

I too am very curious as to why. If you intend to suspend your speakers (which in and of itself is... creative) I'd be far more comfortable using a seperate line for the purpose. A copper wire ought to be fine holding a small box speaker or something of that nature, but I'd not be comfotable putting more than 10 lbs or so on it.

Thanks.
If you really must know, I'm in the process of taking down a hanging ceiling in my basement. There's a large 4-bulb florescent fixture that connected to the ceiling framework. I don't have any chains to hang it with and needed something temp. until I get some chains or replace the fixture. It hasn't fallen yet!

I'd get some picture hanging wire, it's what holds up the suspended ceiling in my basement so I trust it.

the copper strands in wire are probably cold-worked considerably during the drawing process.

the yield strength for copper is ~70Mpa annealed, and ~310Mpa for highly cold-worked copper.

its probably safe to say that the Yield strength is somewhere between those values.

18 AWG has an area of .823m*10^-6

using 190Mpa as the yield strength, the wire should be able to support 156N of weight. (35 lbs)

and failure will probably occur around 50 lbs

your wire should be fine to hold a ~20 lb light fixture.

Neat! Science!

Even so, I'd probably double it up a few times. Distribute the weight over as many strands of wire as you can.