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Tech Tip Of The Day: The Mystery Of Fuses

What is meant by "the continuous load on a fuse in an enclosure should not exceed what percent of it's rating"?

Provided by Sweetwater.

Q: I have what may seem like a silly question, but I’ve been racking my brain and I can’t seem to come up with the answer. Well, not really a question, really, but I keep getting confused by this:

“The continuous load on a fuse in an enclosure should not exceed what percent of its rating?”

You see, I’m doing some work, and I noticed that the above question does not indicate enclosure size, which in my experience has a profound effect, nor does it indicate whether or not the enclosure is vented.Any thoughts you have would be greatly appreciated.

A: Well, using what you’ve given me I’ll do my best. However, your question doesn’t really specify what you mean by “enclosure.” My house is an enclosure. I presume you mean loudspeaker enclosure, but even that is rather vague, as you suggest.

What size? What types of drivers? Is there a passive crossover in play? You also don’t specify the properties of the “continuous load.”

Is it DC, sine wave, uncompressed/compressed music? What exact malady are you trying to prevent? One would assume you are trying to prevent too much current/power from blowing drivers, but you could also be trying to prevent a shorted driver from harming a power amp (old amps didn’t have the protection circuitry of today’s modern designs).

A fuse wouldn’t be much good for anything else, but we still can’t really assume this.

So, since it’s unlikely I can directly answer your question, I’ll just explain what a fuse does and hopefully we’ll stumble upon the answer you need while helping everyone else a bit in the process.

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