Fusing Speaker Outputs

[Aaron407 10+ year member]

Hey everyone, sorry if this has already been asked:

I want some extra protection against blowing my subs, so I'm fusing the speaker outputs on my amps. I want to use a 7.5A inline fuse with a 4ohm sub. With P=(I^2)*R, this should theoretically limit the power to 225Wrms. Is this a correct assumption, or are there other factors to incorporate?

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[helotaxi 5,000+ posts]

Don't waste your time. The best protection for your subs is making sure that you don't clip the signal. As long as you are giving the subs unclipped power they can handle a lot.

 

[maylar 10+ year member]

Fuses were used in the old days to protect speakers from catastrophic amp failures. Like shorted output transistors that would put DC on the voice coil and burn them out. Modern amps have fast acting protection circuits that shut down the power supply for those kinds of failures. Fuses are not needed.

 

[Aaron407 10+ year member]

One of the amps I'm using doesn't have a protection circuit. Anyway, why would it take several minutes at 450 watts rms? Shouldn't the fuse blow when the current exceeds the fuse rating? Sure they're slow blow fuses, but I don't understand how it could take minutes.

 

[helotaxi 5,000+ posts]

Even a fast blow fuse will flow its 110% of its rated current for a few hours. It will flow 200% of its rating for a few minutes. That is the way fuses are rated. Unless you vastly exceed the the rating of the fuse you won't blow them on music.