I read a post earlier today where someone was recommending that they have their speakers recapped. Just what does that involve and why would you do it?
Depends on who you ask. There is a consensus in the subjective listening crowd that says the materials of a capacitor affect its sound quality and thus the music quality. It's an idea that is more prevalent in the active circuits of a component than in a loudspeaker but the idea of the capacitor's "sound" is similar no matter where the cap exists.
Caps do wear out and dry out. Mostly from disuse but also simply over time. Passive components such as caps and resistors will suffer from "drift" and their values will eventually reach an out of spec point. It will typically take a decades or more for this to occur. As far as specs are concerned, no one I know of uses 1% caps in a loudspeaker crossover. More like 10% OEM in most systems. So, if the cap reaches 11-12%, how much worse is that?
There is also a very slight resistive component to any capacitor due, primarily, to the lead outs. If you are very serious about meeting specs, it's a pretty safe bet all but the most fastidious manufacturer will not really take the resistance factor of a cap into account in their design. A very few loudspeaker manufacturers do use less apparent values such as their internal cabling into account when they spec a system but that's the exception rather than the rule.
If you are using or buying twenty five year old loudspeakers, you might want to consider new caps. Otherwise, what you perceive with a cap change is relative to your subjective beliefs.
Not at all. The cost of X-over caps can vary from a few dollars to plenty times that.
You would need to select the appropriate brand of cap for the job and go from there. Then you need to find someone willing to do the work. This can mean a fair amount of disassembly of some speakers.