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Discussion Starter · #1 ·
so i have a completly stock 2001 focus zx3 with everything but no sunroof and i was wondering if i would need any thing like a bigger alternator if i were to hook up a

dual 12 inch 1200 watt sub
aftermarket rockville rvd7.0 headunit
4 6x8 rockville 320 watt rms and 1280 peak watt speakers
and 2 7 inch rockville headrest monitors

i just would like to know because im new at modifying cars
 

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C2H5OH
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Amps = Watts / Volts


Nothing you're buying will reach the wattage you're listing. Economy audio products are notorious for lying about their specs.


But, you'll be fine on the properly working stock alternator.
 

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Strichmädchen & Koks
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LOL @ 320 watt RMS 6x8 speakers.

They'd probably catch fire if you even thought of feeding it that much power.
 

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Strichmädchen & Koks
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Also, it should be pointed out that the watt rating on speakers and subs has zero bearing on how much power they use. That rating is purely for pairing them with an appropriate amp so they 1) have enough power to actually work correctly and 2) don't get too much power from the amp.

You need to look at what your amp draws and use that for figuring out power levels. Also, what the amp is rated at and what it will actually put out are very often two different things. If the amp only has a 40 amp fuse, but is rated to put out 1000 watts of power, then something ain't right. 40 amps x 12 volts = 480 watts. Nowhere near 1000 watts.

Regardless, unless you're spending serious money on a serious system, you don't need to change the alternator.
 

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Premium Member
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Welcome to FF AngryEagles!

I'll move this to the Car Audio section where you can find more info. on setting up Stereo systems.
 

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Vince your Moderator
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Also, it should be pointed out that the watt rating on speakers and subs has zero bearing on how much power they use. That rating is purely for pairing them with an appropriate amp so they 1) have enough power to actually work correctly and 2) don't get too much power from the amp.

You need to look at what your amp draws and use that for figuring out power levels. Also, what the amp is rated at and what it will actually put out are very often two different things. If the amp only has a 40 amp fuse, but is rated to put out 1000 watts of power, then something ain't right. 40 amps x 12 volts = 480 watts. Nowhere near 1000 watts.

Regardless, unless you're spending serious money on a serious system, you don't need to change the alternator.
Plus you do not mention amp efficiency, most A/B amps are only 60-70% efficient. Class D amps, 70-80%.

Now to the OP(orignal poster), you did not mention what amplifier that you are using.
 

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Dat boxer rumble
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It looks like Rockville is a pretty crap company-

Nobody makes a 360w RMS 6x8 speaker. Even the super-high end speakers only go up to ~100RMS. I assume that they are multiplying the RMS on the speakers, which would mean that each speaker can only handle 80RMS, but when you consider that they are likely overrating their speakers, they can probably only handle about 60rms, which is on par with most "walmart/ebay/chinese crap" brands.


Also, you havent posted what Amp you plan on using. Replacing your door speakers wont do much unless you give them a dedicated Amplifier for them.


Can you give us an idea of what kind of budget you have? We can guide you into a decent setup that will actually give you some decent sound quality and punch.
 

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Guys, just a heads up on amp ratings… The actual draw of the power supply is almost NEVER a 1:1 ratio with what the amp is capable of outputting to the speakers… The big factor is always the design of the power supply. There are about 4004034906u34503458348 ways that output power is tested (as well as power handling on speakers), so it's pretty hard to actually trust ANY advertised numbers. Generally, a reputable company will use some sort of "standardized" test to determine the numbers, and that's always more of a guideline.

SO, to answer your question, if you're trying to figure out what your system is going to be drawing from the electrical system, add up all the values of the fuses on your amp, head unit, and other components, and that will give you the worse case, just before everything catches fire, scenario. If your charging system is healthy, you can run a pretty large system on it before you'll need to upgrade your alternator. A good Capacitor will help keep your alternator happy as well.
 

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Dat boxer rumble
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Guys, just a heads up on amp ratings… The actual draw of the power supply is almost NEVER a 1:1 ratio with what the amp is capable of outputting to the speakers… The big factor is always the design of the power supply. There are about 4004034906u34503458348 ways that output power is tested (as well as power handling on speakers), so it's pretty hard to actually trust ANY advertised numbers. Generally, a reputable company will use some sort of "standardized" test to determine the numbers, and that's always more of a guideline.

SO, to answer your question, if you're trying to figure out what your system is going to be drawing from the electrical system, add up all the values of the fuses on your amp, head unit, and other components, and that will give you the worse case, just before everything catches fire, scenario. If your charging system is healthy, you can run a pretty large system on it before you'll need to upgrade your alternator. A good Capacitor will help keep your alternator happy as well.
Very true on the input/output numbers. It's difficult to measure the exact performance of an amp, which is why most car audio guys joke that you might hit the RMS Peak if your car was struck by lightning while playing a loud song at full volume.

That being said, many manufacturers (Im looking at you Pioneer) make RMS claims that are completely irrelevant to the actual performance of their products.

Ex- I found out the hard way that my Pioneer sub rated at 450rms, couldn't handle my 300rms amp. Thank god for walmart's return policy, i blew about 4 of them before giving up and buying a Polk sub (which worked perfectly and is still kicking).
 

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Vince your Moderator
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This is why I love a test disc, my oscilloscope and warranties.
 

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Vince your Moderator
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The CEA ratings are what you will get out of it. You have a 200 watt sub system. The deck will put out 10 watts a channel. Total system power=240 watts RMS
 

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You would be better served skipping all those. They arent cheap besause its an authorized dealer it is cheap because its cheap. And honestly just bad
 
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