I have an old ~1990 pair of KG4's that are just not sounding very good (after many years of great sounds). When I switch from left to right channel, I can definitely notice that one of them is not producing all of the tones. I am wondering (1) how do I go about testing the speaker's different components? (2) if various things need to be replaced, should I do this myself, find a speaker store, or suck it up and buy new speakers? I don't know much about speakers (in case you can't tell), so I'm looking for some advice that will help me proceed. I also searched around this site and see that the speakers seem to hold their value. I've gone through a bunch of "how do I test my speakers" links online, but thought that folks here might have some good ideas. Thanks!