Originally Posted by TiredHornet
Is the "driver pad" the place where the cables where soldered to the driver?
Yes. "Pad" is short for "solder pad", which means an exposed bit of metal intended to be soldered to.
The solder wouldn't stick to the plug. I was told this has to do with me having solder without flux.
If the solder smokes when you touch your iron to it, it has flux. Solder without flux is very much the exception.
Some people find it helpful to add liquid or paste flux to a joint. I have found it helpful myself, but on cables, it's typically only because I've spent too long on the joint so all the flux has been burnt off.
More typically, problems with getting solder to stick to a connector comes down to not being able to get enough heat into the solder lug quickly enough. This is not to say that you need a hotter iron, but that you need one that has less sag in its heat output when you touch it to a big lump of metal. A hotter iron can have the same net effect, but you have to be careful to avoid overheating things. With 1/8" connectors, the risk is melting the plastic insulation that keep the 3 separate connections separate.
So unless, the heat travelled down the 4 foot cable from the plug, I don't know how I could have damaged it.
HiGHFLYiN9 is right: you didn't overheat the driver through the cable.
However, there are many other ways to kill headphones.
With headphone cable, I'd guess the main causes have to do with not understanding how stranded wire behaves under physical stresses.
When you solder to stranded wire, it wicks the solder away from the actual joint, bonding the strands together for some distance past the obvious part of the joint. This makes that section of wire brittle. You must apply strain relief after that point, else you can break the wire with tugs that the stranded wire would tolerate.
But just as bonding all of the wires together makes them more brittle, so does not keeping them close enough together. If you fray the wire a bit near the joint, it allows you to break the wires individually. This is the same principle behind the "rip a phone book in half" trick.
I didn't see any alternative...
I gave you one already: make a project of replacing several 1/8" plugs before graduating to work on the driver end of the cable.
should I assume the driver is toast?
No, you should measure it and find out.
The solder is a bit grayish with some brown dots.
Grayish means you probably burned off all the flux while making the joint, which makes it turn pasty, which makes for a bad joint.
The brown dots are burned flux. They're not a problem in themselves, just a symptom. If the joint were shiny, you'd have every reason not to worry about the burned flux, except insofar as you should clean it off afterward. Burned flux is somewhat conductive -- you've carbonized it, and carbon is a conductor -- and flaky, so it could fall off and short something out.