Following this thread. The twisting/braiding appears to be highly important and it seems people are using a far heavier gauge wire than is needed.
It is the total resistance that governs. R = rho*L/A, where rho is resistivity. The ratio L/A (length area) is the important quantity.
If the attached link works (
http://www.calmont.com/pdf/calmont-eng-wire-gauge.pdf), you will see that a 1.2 mm diameter wire (18 gauge) has just 0.002 ohms resistance per 10 cm, or 0.004 ohms for a 10 cm pair (current going out and back from speakers). This is negligible; about 0.1% of the outgoing power is consumed in this example (using a 4 ohm speaker) and it adds no distortion. For a 4 meter speaker run, you would need to use 2 gauge (10 mm diameter) wire for a similar loss. Some may do this, but it is absurd.
Hence, go with a lighter (say 16 gauge, 1.3 mm diameter), highly stranded wire (speaker wire comes to mind) and concentrate on the twisting and wire orientations as recommended by Julf.
As far as solders and connectors, do try to avoid dissimilar metals, but if it can't be avoided use (carefully) a conductive (anti-corrosion) grease. People use it in marine electronics for a reason.
Do NOT use 'dielectric grease' - it is insulating and meant for high voltage applications (like an engine spark plug). Avoid zinc-bearing greases. I use No-Ox, inherited from my Dad, who used on our boats from the 1960's onwards. Cheap enough, and you can pass it on to your kids. From their web-site:
"Stereo enthusiasts and hobbyists love NO-OX-ID...
How hobbyists and some companies use NO-OXID A-Special, and some Testimonials:
1.NO-OXID A-Special works absolute wonders on audio connections, especially on those pesky RCA connectors that tend to corrode on the inner surfaces of the ground shell, 1/4 phone and even USB connectors
2.Telephones – Telephone companies have been using NO-OX-ID for seventy years.
3.Tinning stranded wires destined for mechanical compression-type connectors defeats the purpose of the mechanical compression. When you insert a set of bare copper wires that are clean and protected with stuff like NO-OX-ID into a speaker thread-type compression connector, the resultant force of the compression on all the strands is what makes a good connection.
4.A quote from a Bell Systems manual on making a connection: "The mating surfaces of the connection shall be burnished to a bright metallic finish and coated with a thin layer of NO-OX-ID anticorrosion paste to preserve continuity indefinitely."
