I'm using recycled cables for this - I've installed a few rack-mounted servers recently and they all came with some incredibly long power cables with a variety of foreign power plugs on them that were not needed. The cables themselves are of quite high quality, being a soft grey texture on the outside and very flexible.
I have taken these cables, cut the plugs off both ends and am reusing them as heavy gauge speaker cables. They have three insulated strands inside the cables, I originally considered using a single cable per speaker, and leaving the earth cable disconnected but I realised I had just enough to run two cables per speaker, utilising all three conductors in a single cable for each of positive and negative.
Step 1: Ingredients
You will also need the following items:
Cable - Despite what a lot of very enthusiastic people claim, by far and away the main factor in the performance of a speaker cable is it's resistance. More copper = more better.
Banana Plugs - this assumes you’re A/V equipment accepts banana plugs. Most mid to high end stuff does. I got a set of "genuine Nakamichi" banana plugs off eBay. They were $2 each, including shipping. I don't care that they're not what they were sold as, for two bucks, they're great value. You need four for each channel (two for each end)
Heatshrink - The banana plugs I got had aluminium bodies. I'm not too keen about them shorting out and blowing up my amp. Heatshrink is cheap, it adds strain relief to the cable and it improves the look. The heatshrink I used has hot melt glue inside it too to hold it in place when it's shrunk. I had this stuff lying around so it cost me nothing, but even so it's pretty cheap stuff to buy.
Miscellaneous tools - screwdriver, side cutters, snap-off blade, source of heat.
There have been well publicised blind listening tests where "golden eared" listeners couldn't tell the difference between expensive, hand made on a mountain top by monks under the light of the second full moon in a month and costing $1k per metre cables and... ordinary coat-hanger wire. Now, coat-hanger wire is a little too stiff for my liking and I had some beautifuly flexible cable, so this is what I started with. You can use mains cable, you can use lamp cord, you can even use actual speaker cable if you wish - it'll all sound better than the tiny thin wires that are delivered with a lot of sound systems.
Step 2: Banana Plugs
As mentioned previously, you need four plugs for each run of cable. Two on each end, one red and one black.
Step 3: Cut Your Heatshrink to Size
As mentioned above, this heatshrink also has hot melt glue inside it so it stays in place very well once it's heated up.
Step 4: Strip the Ends of the Cable
Twist the bare ends together firmly and cut to length to fit the banana plugs.
Step 5: Terminate the Cables
You need to make one cable with red plugs on both ends and one cable with black plugs on both ends for each channel.
Step 6: Heat and Shrink the Heatshrink
You can use whatever heat source you have handy - I used the open flame of a gas stove, a lighter works in a pinch (but is not ideal as you will probably burn the heatshrink a bit and make it look dodgy) a hair dryer probably doesn't get hot enough but if you have a hot air gun this is perfect.
When doing this, rotate the cable in the heat evenly to ensure it shrinks all around, and if you have adhesive inside the heatshrink, make sure it gets hot enough for the glue to melt and flow into place properly. This will make an airtight, watertight seal.
Step 7: Nearly Done
If you do this, make sure the extra heatshrink is not on the red and black ends, as it may split (as I found out)
Also, make sure that it's far enough down the cables that you can separate the red and black plugs enough to plug into your amp or speakers.
Step 8: Finished.
Power down you’re A/V equipment, plug in your new cables and marvel at the wonderful new sound.