# Need electrical help



## Biscuit (Mar 5, 2005)

I am thinking of purchasing a Power Acoustik LT1920/2. It runs 370 watts @ 4 ohms, I think 420 watts @ 2 ohms, and 840 watts bridged. I need to know what I am going to need to power this monster in my 89 Sentra. Would I need a cap, beefed up alt, or deep cycle battery? A friend has told me that you will have to have your alt put out 100 amps per 1 thousand watts. How many amps does my alt run. I just bought it a year ago and I dont know how many amps it puts out.


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## sr20dem0n (Mar 19, 2003)

Assuming that amp actually puts out rated power, which I highly doubt it does, you would probably be fine with just the big 3. I really depends on how you listen to your music though, the output capabilities of the amp are pretty meaningless when it comes to the impact on your electrical system. Person A could be perfectly fine with a 2500rms system on the stock alt and batt, while person B could have serious electrical problems with only a 500rms amp, a cap, and a new batt. All depends on their listening habits.


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## Biscuit (Mar 5, 2005)

Its does put out rated power. Bunches of people say that they may be a itty bitty bit overrated but not likely. People like them so I guess it does put out rated power. What is the big 3?


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## sr20dem0n (Mar 19, 2003)

A lot of people like Sony and Bose too, doesn't mean they're any good

The big 3 is upgraded wiring under the hood. You would add a cable from the batt - to chassis, engine block to chassis, and alt + to batt +, using 4awg cable or larger.


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## Chris90FB240sx (Feb 25, 2005)

Yea 800 bridge isnt pulling much. Ive got a 600 Alpine and Im using a 6 gauage which is actually kinda small but it pulls the power needed. And it doesn pull to hard on the batt. My lights dont dim much at all under full load of the subs. The deck lights dim some but not much. Now if you have some dimming you may want to go to a cap. 

Ive seen 6 15s pushed by just Upgraded Altenator. The lights dim alot but it worked. LOL 
If your car has trouble with hard bass lines for the subs Id go to a single cap just so it will help the altenator on those loads.


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## shock211 (Feb 28, 2005)

hook it up and test your battery to see what voltage readings you get with the car running at idle. hopefully no less than 12.1v with a system like yours.
your alternator is based on what size engine you have, power features and luxury features. a sentra in 89 probably ran a 60a - 75a alternator.


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## Biscuit (Mar 5, 2005)

So All I need is a cap right? I aint going to be using this system to the point of deafness.


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## Chris90FB240sx (Feb 25, 2005)

If your worried about the cars batt and amp being put under to much strain.

Yes get a cap. :thumbup: Cheapest solution.


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## sr20dem0n (Mar 19, 2003)

no, don't waste your money on a cap

It will not lighten the load on anything, it will not reduce the strain on anything....that's not what it does. All it does is smooth out the voltage, so if your electrical system is normally fluctuating between 12 and 14v, a large cap might even it out to a constant 13v, but the exact same load is still being placed on the alternator and battery. Instead of your lights flickering between bright and dim, they might just stay at a constant semi-dim state.

I repeat, don't waste your money. The big 3 will actually _reduce_ voltage drops, not just even them out so the voltage is always slightly "dropped", and it's 1/10th the cost.


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## Chris90FB240sx (Feb 25, 2005)

The cap is made to help the Batt during heavy pulls from the Subs... Why would it not help the Altenator and Battery?? Subs dont always pull the full power needed... I dont think a 800 watt amp will pull enough anyway to do anything to the altenator or battery. Its most likely not true watts and Im running a 600 that doesnt pull much at all.

Personally Id see how the car acts with normal bass and when you hit hard bass see how it acts. If it dims in hard bass but is normal the rest of the time, I personally would get a cap because that is what the cap is made for big pulls for bass.


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## Punkrocka436 (Jul 8, 2003)

Chris90FB240sx said:


> The cap is made to help the Batt during heavy pulls from the Subs... Why would it not help the Altenator and Battery?? Subs dont always pull the full power needed... I dont think a 800 watt amp will pull enough anyway to do anything to the altenator or battery. Its most likely not true watts and Im running a 600 that doesnt pull much at all.
> 
> Personally Id see how the car acts with normal bass and when you hit hard bass see how it acts. If it dims in hard bass but is normal the rest of the time, I personally would get a cap because that is what the cap is made for big pulls for bass.


Think about it this way. Whenyour lights are dimming, there is too much of a load on your electrical system. You will agree with me on that right? Why would you add ANOTHER component to the electrical system and hurt it even more? Sure the lights dont flicker, but they are still dimmed, and its placing an even bigger load on your electrical system. 

Trust us on the big 3. I had dimming issues with my IDQ10 on 400 watts, upgraded the big three, no more dimming, and no added strain to the electrical system.

The only reason to get a cap is to smooth out the voltage to the sub amp ON A SUFFICIENT ELECTRICAL SYSTEM. If you have dimming issues the first thing to do is upgrade the big three with 4 gauge or bigger, if that doesnt help upgrade to a deep cycle battery, and if your still having issues, a High output alternator.

Chris- seriously man, get a clue. sr20dem0n is the resident audio guru, and if he says soemthing, usually its because he has spent countless hours researching it. Caps are talked up by the retail stores because it costs them 20 dollars to buy, and they sell for 125+ in CC and BB. They are a bunch of hype. You sound like an audio newb that read a little bit, and is automatically a professional.


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## sr20dem0n (Mar 19, 2003)

Chris90FB240sx said:


> The cap is made to help the Batt during heavy pulls from the Subs... Why would it not help the Altenator and Battery?? Subs dont always pull the full power needed... I dont think a 800 watt amp will pull enough anyway to do anything to the altenator or battery. Its most likely not true watts and Im running a 600 that doesnt pull much at all.
> 
> Personally Id see how the car acts with normal bass and when you hit hard bass see how it acts. If it dims in hard bass but is normal the rest of the time, I personally would get a cap because that is what the cap is made for big pulls for bass.



Where do the caps get their energy from? When they supply all this current, where do you think they get the current to refill from? All they do is spread the load on the alternator over a longer time period, so instead of the alt/batt having to provide 100 amps for 1 second, they now have to provide say 50 amps for 2 seconds (actually it's higher than this because they have to cover the cap's internal losses as well). The total current draw, power consumption, everything is the same. The only difference is with a cap the load is smaller and lasts longer. So, like I said before, instead of your voltage fluctuating between say 14V and 12V, it now hovers at a constant 13V. On big bass hits they'll immediately drop down to the batt's voltage and become another load, the ONLY time they'll do anything is when your electrical system is strong enough to support the sustained current draw from your amps, it just doesn't have the reaction time to handle extremely fast transients. The chance that a cap is the only (or cheapest) solution to a problem is less than 10%, people just think that they're some magical device that fixes everything on the face of the earth.
"dimming problems? get a cap!"
"amp shutting off? get a cap!"
"car ran out of gas? get a cap!"
"dog broke its leg? get a cap!"

You can thank the greedy retards at local shops for starting the stupid cap craze.


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