The capacitors in a crossover–along with other components–act as filters, so that each driver in your cabinet gets the right range of frequencies. These capacitors have roughly a 20-year lifespan before they begin to drift. This can cause problems anywhere from subtle to dramatic changes in how your speakers were intended to sound.
We’ve yet to meet a twenty-year-old speaker we couldn’t instantly improve upon. Newfound clarity, detail, and separation beckon. The next move is yours.