Speaker Cable vs. Instrument Cable

[Zaphod B]

When I picked up a bunch of equipment that had been sitting in a friend's basement for a few years, I ended up with a several cables of varying length with 1/4" mono jacks. Some are labeled as instrument cable, some as speaker cable, and some are not labeled at all.

I understand the different requirements for the two types, but for short runs does it really matter which you use? And if it does, how can you tell an instrument cable from a speaker cable?

 

[Zaphod B]

I guess it's the conductors.

Instrument cable would have a single center conductor, well insulated, with a braided shield.

Speaker cable would have two conductors with no shield.

Correct?

 

[toobalicious]

but for short runs does it really matter which you use?

yes.

well, it depends. you should never use an instrument cable for a speaker run, even a short one. instrument cable will usually (because some yahoo somewhere, breaks the rules) have small gauge wire which is problematic for speaker runs because:
(a) it physically may not be able to carry the current, causing failure (possibly a dead short) which can kill some power amps, start a fire, or at least blow the fuse
(b) is made of coaxial (and hopefully shielded) cable (like the stuff you plug into your TV), which creates a capacitive load, and *that* will at best destroy the amp's control over the speaker (poor sound) or just cook the output section all together (especially some tube amps).
the biggest and only reason not to use speaker cable as an instrument cable is that it will be noisy as all hell in a high impedance setting. speaker cables can get away with no shielding because with the low impedances and high currents that speakers operate, induced noise isnt a factor.
a

 

[Zaphod B]

Cool, got it, thanks.