alt Hacker NewsWhy wouldn't mains cable make good speaker wire? Probably much larger diameter than needed for audio and therefore more expensive if fairly priced, but if you've got to wire speakers and that's what you've got, should be fine.
About the only things you could do wrong would be using wire that's too small to carry the load, is frayed/broken/severely corroded, or is coiled in a way that inductance becomes a real issue. Running parallel and near electrical or signal wires is problematic, and largely different run lengths can make a difference.
In the past, there was no special speaker wire. It was all mains wire, because all was 100% copper. Today, finding 100% copper cable having the cross-section stamped on it is pretty rare. Electronics being more efficient hence drawing less power allows manufacturers to run 3-4 copper clad aluminum strands as mains cable in some cases.
Today, I'd still use "mains wire" if I can find it in a 100% copper form with the correct cross section. The reason I used "speaker wire" in my set is because the recommended cable was thicker than the standard stuff, and I didn't believe that I'd be able to get 100% copper wire easily.