fuse

[Benny212 10+ year member]

I had this idea and was wondering why I haven't seen anyone else do it.

use the formula power/impedance=current^2 to find how much current is running to the subs. then put a fuse between the subs and the amp. so for a 450 rms sub with an amp that can put out more than 450 rms it will keep me from blowing my sub

450/2=I^2

square root of 225=15

so if I put a 15 amp fuse between my sub and amp it will blow when I put more than 450 watts through it.

Please let me know if there is a flaw in my plan or the reason why noone does this.

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[maylar 10+ year member]

Your formula is correct. Nobody fuses speakers because the amp driving them is already fused. Your gains should be set such that it's impossible to hurt the speakers.

 

[forbidden 10+ year member]

And fuses can carry much more than their rating for breif periods of time, thus excessive output or clipped signals can still make it to the speaker. Maylar has the proper suggestion, set the gain properly.

 

[Benny212 10+ year member]

And fuses can carry much more than their rating for breif periods of time, thus excessive output or clipped signals can still make it to the speaker. Maylar has the proper suggestion, set the gain properly.

even on fast blow fuses?

and how can you tell exactly what the right setting on the gain is to put out X amount of power without tools that a normal person wouldn't have?

 

[helotaxi 5,000+ posts]

The older Orion amps (the really big ones) used a pigtail for the speaker outputs and they were fused. I blew those fuses more times that I care to think about and the subs were never in remote danger. It was a royal pain and not worth it.

To set your gain, you really only need a digital multimeter, which if you are working on your stereo regularly, you should have as a normal person. JL audio has a really nice tutorial on it on their site. In a nutshell, solve the power equation for volts and disconnect your speaker from the amp. Set you HU volume at about 2/3's volume (this is the ballpark area where most HU's start to clip their preamp outputs, lower if a loudness circuit is enabled or if you have the bass or treble controls turned up) and amp gain to min. Connect the leads to the DMM to the speaker outputs with it set to AC volts and RMS. Slowly turn up the gain until you get the voltage required for the power level you want. Turn everything off and reconnect the speaker and you're good to go.