What are electrolytic caps?

I have a pair of Spica TC-50s (circa 1989). I was reading an interview with John Bau (inventor of the Spica speakers). He says in the interview that the "electrolytic caps go south after about a decade."

1. What are electrolytic caps?

2. What does he mean they "go south after a decade"? Does sound quality significantly decrease?

3. Are the caps something I can easily replace and how? Sounds like you need to get a matched pair with tight specs.

Thanks for your help! The interview link and quote are below.



http://www.enjoythemusic.com/magazine/equipment/0900/spicafever.htm (quoted section below)

Quote from interview:

JB: For TC-50 and Angelus; replacement of the electrolytic caps with film types will help (they start going south after a decade or so anyway). Exact design values should be used (not the values printed on the parts; we batched all our components to better than 0.1% groups, and paralleled them to achieve exact values). I'd have to dig up the schematics to find the target values.
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).
Thanks for the reply! I had no idea that capacitors actually leak over time.

It's very hard to tell if the speakers sound any different since I've been listening to them for over 10 years now. They could have slowly been deteriorating over the years and I wouldn't have noticed. For the most part they sound fine to me, though. Maybe a little quiet... but that just may be how the Spica's are.

Sounds like replacing the capacitors (and even getting the right ones) is very difficult. I'm better just keeping the things the way they are unless something sounds obviously wrong to me.

Thanks again for the info!
It's more that they dry up, rather than leak, in the case of Electrolytics.

Drying out makes sense, too. Especially over a long time period.

What are film capacitors? Are they also hard to find matched pairs? John Bau recommended switch to film caps.

Is it worth the effort to try and find someone who can get me a matched pair(s) and replace them in my Spicas?

Sounds like Spica spec'd out their own capacitors from a batch. I'm not sure how I would even start to find an adequate replacement. This is all over my head a bit!
My Spica TC-50's are about 15 yrs old and have no problem whatsoever with the crossovers. The tweeter on one did 'head south' and I replaced both with a set from Madisound.