I'm no expert but if your solder joint is gray or looks like a bubble gum blob you may want to resolder. Solder joint should be shiny or mirror like. A solder sucker is your friend. I've always found when you tin stranded wire it should be totally soldered through out the wire but should be able to see each strand of wire, place a small amount of solder in cup heat cup up, place tinned wire in cup let it become one still able to see each strand of wire, pull on wire for durability and your done.
Ive made my own wire for ten years or more some can sound very nice but never have been able to compete with high end wire. I've used stranded, solid silver, solid and stranded copper, magnets, vibration control but it's very tricky to make wire that can compete with $1000 and up cable. Power cables seem to be the easiest to make sound good. Use nice quality connectors good wire and some clamps and vibration control and they can sound pretty good for what they are.
For speaker wire wire I use bare wire. In one system I have speaker wire hard wired to amp and outboard crossover. No bulky big copper binding post.
