1. Capacitors that use an electrolyte (thick liquid) that can leak out of them over time.
2. Their capacitance falls if they leak. Since yours are in a crossover this would change the frequency and phase response of the crossover. The amount by which specific caps leak and the effects on sound quality would be very difficult to predict. If your speakers still sound OK to you then they're probably OK. I know it's kind of hard to tell but do you think they sound worse than when you bought them?
3. In the case of Spicas I believe it is particularly difficult since the values are not printed on the caps, and they use odd values by paralleling caps to get exact design values. It sounds like a tricky proposition, and you'd need an accurate capacitance tester (not cheap).
2. Their capacitance falls if they leak. Since yours are in a crossover this would change the frequency and phase response of the crossover. The amount by which specific caps leak and the effects on sound quality would be very difficult to predict. If your speakers still sound OK to you then they're probably OK. I know it's kind of hard to tell but do you think they sound worse than when you bought them?
3. In the case of Spicas I believe it is particularly difficult since the values are not printed on the caps, and they use odd values by paralleling caps to get exact design values. It sounds like a tricky proposition, and you'd need an accurate capacitance tester (not cheap).