12.22 What size fuse or circuit breaker should I put in my speaker to protect it from damage?
Description
This article is from the rec.audio.* FAQ, by with numerous contributions by Bob Neidorff others.
12.22 What size fuse or circuit breaker should I put in my speaker to protect it from damage?
Most modern speakers consist of a box containing more two or
more drivers interconnected through a network of inductors,
capacitors, and resistors. One fuse or circuit breaker in
series with that array can't possible protect all drivers.
Conventional circuit breakers are a very bad choice for speaker
protection. They add series resistance, series inductance, and
lousy electrical contacts, all tending to degrade performance.
Moreover, breakers have a trip characteristic that does not
match the damage mechanisms of speakers.
Fuses are a better choice, but still are not very good. This
is because speakers have complex thermal behavior. Loud
playing will warm up the voice coil making it more sensitive to
damage. No fuse takes this into account correctly. A fuse
will do a better job of protecting tweeters, but is still not
perfect.
If you want to protect a speaker with a fuse, use the lowest
current, fast-blow fuse which will not blow during normal
listening. This may trip prematurely in a very loud passage,
or may degrade sound quality, but it is your best bet for fuse
protection. For a woofer, start with a 1 Amp fuse and work up.
For a tweeter, start with 100mA and work up.
There are also cheap tweeter protectors available which contain
a light bulb and a resistor potted in a small tube. They work
pretty well, and if you reduce the tweeter network's series
resistance by a few tenths of an ohm, they are not terrible for
the sound. But they are audible and not failsafe.
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