# Basic question about calculating RMS and total wattage of my set up

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#### Hags222

##### CarAudio.com Newbie
This question may be quite straight forward, but I cannot find an answer anywhere. I am new to this forum but I found the formula to ballpark estimate my total amperage. I do not understand one part. When you calculate this, do you add up the total RMS of the amplifier AND the subwoofers it will be powering, or does the RMS of the amplifier translate into the subwoofers and therefore I just use the RMS of the amplifier? I got an 8AWG power wire and ground wire for my soundstage SS500.1 and a soundstage dual 10” boxed subwoofer with an RMS of 500W and peak 1000w. I am now kind of doubting if my power wire be suitable for a small car, can anybody help?

Your amplifier is what is consuming amperage. 8 gauge OFC wire will be fine for 500 watts rms. A good 8 gauge OFC wire is rated for 60 amp load in a 20’ run.

Your amplifier is what is consuming amperage. 8 gauge OFC wire will be fine for 500 watts rms. A good 8 gauge OFC wire is rated for 60 amp load in a 20’ run.
Great thank you very much. Also, do you know if the fuse i should be placing near the batter would be fine if I use a 40 amp fuse? or should I use a 60 amp. There are x2 30 amp fuses located directly on the amp, but if I am correct these do not protect the wire?

Correct. The power wire fuse should be close to the battery. A 40 amp will be fine.

This question may be quite straight forward, but I cannot find an answer anywhere. I am new to this forum but I found the formula to ballpark estimate my total amperage. I do not understand one part. When you calculate this, do you add up the total RMS of the amplifier AND the subwoofers it will be powering, or does the RMS of the amplifier translate into the subwoofers and therefore I just use the RMS of the amplifier? I got an 8AWG power wire and ground wire for my soundstage SS500.1 and a soundstage dual 10” boxed subwoofer with an RMS of 500W and peak 1000w. I am now kind of doubting if my power wire be suitable for a small car, can anybody help?
Add the amperage of the fuse ratings on the amps. If your mono amp uses 2 30amp fuses and your voice amp uses 2 20amp fuses, that will be- 30+30+20+20=100. So an 100amp fuse and correct awg cable.

Add the amperage of the fuse ratings on the amps. If your mono amp uses 2 30amp fuses and your voice amp uses 2 20amp fuses, that will be- 30+30+20+20=100. So an 100amp fuse and correct awg cable.

How is my answer wrong? He is looking for total amperage to protect the cable run. If your amp uses 60 amps, you are not going to put a 40 amp fuse by the battery. You will deprive that unit of 20 amps. So if he had two amplifiers that use 60 amperes each, you have to fuse that cable with an 120 amp fuse. And of course a thicker cable that can take at least 150 amperes.

How is my answer wrong? He is looking for total amperage to protect the cable run. If your amp uses 60 amps, you are not going to put a 40 amp fuse by the battery. You will deprive that unit of 20 amps. So if he had two amplifiers that use 60 amperes each, you have to fuse that cable with an 120 amp fuse. And of course a thicker cable that can take at least 150 amperes.
I think you might have misread it. I only have one mono amplifier, and the 8AWG power wire i am using is RATED for 60 amps, this much will not be consumed though...

I think you might have misread it. I only have one mono amplifier, and the 8AWG power wire i am using is RATED for 60 amps, this much will not be consumed though...
No, those were just examples, not your particular setup. But you have to rate your supply fuse the same as your amp's fuse rating. If not, you could end up damaging the amplifier. When enough current is not supplied, the amp will heat up when you drive it hard or for an extended period. Have you ever seen used amps with melted power supply terminals? That happens because the wire is not tightened and the amplifier is pulling more amperage than that connection can supply. Another result are burnt mosfets or popping supply fuses. Worst case scenario would be melted supply cable causing a car fire. Even though you will not drive your amp that hard, it is always better to err on the side of safety.

It wasn't. That method works fine. Although not all amps have fuses.

He is looking for total amperage to protect the cable run. If your amp uses 60 amps, you are not going to put a 40 amp fuse by the battery. You will deprive that unit of 20 amps.
That's not really how it works. Fuses aren't like light switches. A 40A fuse will suffice for a ~60A amplifier because the actual current draw of an amp with ~60A max would be nowhere near 60A the majority of the time, and on short term 50-60A peaks the 40A fuse wouldn't cause any problems. Fuses are just short pieces of thin wire. They take time to heat up, melt, and blow.
If you look at fuse specs, specifically time/current plots - ratings are what the fuse will pass basically forever. A 40A fuse would pass 50A for a long time, 60A at least a few minutes, even 80 for a second or so.

It could be argued that the smaller fuse has a bit more resistance and would create extra voltage drop -- yes, but only measurable, no where near audible.

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I did not know that. Thanks. I would be scared to not stick to safety procedures recommended by manufacturers.

@1aespinoza dude just stop.....you are flooding this forum with b*llshit

Get me banned then. Your dumbass has not provided any useful advice in any comment that I have seen so far.

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### Hags222

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