can anyone tell me what exactly caps do and how they work
ill admit im not a stereo whiz kid
i think ive figured out about crossovers , are caps about the same thing just a filter or are they something totally diffrent

any info would be helpful
thanx

 

Are you talking about a bolt cap?

 

In a way, a capacitor is a little like a battery. Although they work in completely different ways, capacitors and batteries both store electrical energy. If you know how Batteries Work, then you know that a battery has two terminals. Inside the battery, chemical reactions produce electrons on one terminal and absorb electrons at the other terminal.

A capacitor is a much simpler device, and it cannot produce new electrons -- it only stores them.

Like a battery, a capacitor has two terminals. Inside the capacitor, the terminals connect to two metal plates separated by a dielectric. The dielectric can be air, paper, plastic or anything else that does not conduct electricity and keeps the plates from touching each other. You can easily make a capacitor from two pieces of aluminum foil and a piece of paper. It won't be a particularly good capacitor in terms of its storage capacity, but it will work.

When you connect a capacitor to a battery, here’s what happens:

- The plate on the capacitor that attaches to the negative terminal of the battery accepts electrons that the battery is producing.


- The plate on the capacitor that attaches to the positive terminal of the battery loses electrons to the battery.


Once it's charged, the capacitor has the same voltage as the battery (1.5 volts on the battery means 1.5 volts on the capacitor). For a small capacitor, the capacity is small. But large capacitors can hold quite a bit of charge. You can find capacitors as big as soda cans, for example, that hold enough charge to light a flashlight bulb for a minute or more. When you see lightning in the sky, what you are seeing is a huge capacitor where one plate is the cloud and the other plate is the ground, and the lightning is the charge releasing between these two "plates." Obviously, in a capacitor that large, you can hold a huge amount of charge.

Here you have a battery, a light bulb and a capacitor. If the capacitor is pretty big, what you would notice is that, when you connected the battery, the light bulb would light up as current flows from the battery to the capacitor to charge it up. The bulb would get progressively dimmer and finally go out once the capacitor reached its capacity. Then you could remove the battery and replace it with a wire. Current would flow from one plate of the capacitor to the other. The light bulb would light and then get dimmer and dimmer, finally going out once the capacitor had completely discharged (the same number of electrons on both plates).

Like a Water Tower
One way to visualize the action of a capacitor is to imagine it as a water tower hooked to a pipe. A water tower "stores" water pressure -- when the water system pumps produce more water than a town needs, the excess is stored in the water tower. Then, at times of high demand, the excess water flows out of the tower to keep the pressure up. A capacitor stores electrons in the same way, and can then release them later.

The unit of capacitance is a farad. A 1-farad capacitor can store one coulomb (coo-lomb) of charge at 1 volt. A coulomb is 6.25e18 (6.25 * 10^18, or 6.25 billion billion) electrons. One amp represents a rate of electron flow of 1 coulomb of electrons per second, so a 1-farad capacitor can hold 1 amp-second of electrons at 1 volt.
A 1-farad capacitor would typically be pretty big. It might be as big as a can of tuna or a 1-liter soda bottle, depending on the voltage it can handle. So you typically see capacitors measured in microfarads (millionths of a farad).

To get some perspective on how big a farad is, think about this:

- A typical alkaline AA battery holds about 2.8 amp-hours.
That means that a AA battery can produce 2.8 amps for an hour at 1.5 volts (about 4.2 watt-hours -- a AA battery can light a 4-watt bulb for a little more than an hour).
Let's call it 1 volt to make the math easier. To store one AA battery's energy in a capacitor, you would need 3,600 * 2.8 = 10,080 farads to hold it, because an amp-hour is 3,600 amp-seconds.

If it takes something the size of a can of tuna to hold a farad, then 10,080 farads is going to take up a LOT more space than a single AA battery! Obviously, it is impractical to use capacitors to store any significant amount of power unless you do it at a high voltage.

Hope this helped

 

I know you can't type that fast. Cut and paste

 

In the capacity that your asking about Polarak it acts as a method of stablizing the power in your cars electrical system. If you've ever had a powerful enough amp in your car (without a cap) you can see the headlights blink when the amp puts a strain on the electrical system. A cap would help with that. The cap would provide that extra power when your amp really starts sucking the juice to push the bass. I have also heard of them being used on head units.

 

I took this directly from www.howstuffworks.com

It's a great site for learning what things do and stuff... its pretty helpful especially with cars.

 

Ah, Kareem...you are wise in many ways. Knowing how to find the answer is equally as important, if not moreso, than knowing it yourself.

The amp only draws from the cap when the power line is being strained too much, right? Or am I misunderstanding the principle? What I don't know about car audio and electrical engineering could fill a book. A really freakin' big book.

 

did someone say electrical engineering?

the cap is pretty much simultaneously discharging and charging. it charges at a significant rate however, since it is connected to the battery. if you get a digital cap, it will show you the voltage. you'll notice that it stays constant until a bass hit, which will draw a significant amount of energy directly from the cap. the reason this is beneficial is because A. it takes time to pull current from the battery to the amp (so a cap is faster) and B. it doesn't take energy away from the battery and other electrical systems. So the benefit of a cap is to keep the bass clean, crisp, and precise, and to prevent the dimming headlights during heavy bass. Obviously if you run too much power, you will need to upgrade your total current supply by getting a bigger alternator, as a cap only provides instantaneous current for bass response (since bass is the heaviest load).

One thing to remember about capacitors is to be very careful when connecting/disconnecting them. a friend of mine was putting a 2nd battery back into his car and had accidently connected it in reverse, the cap discharged energy stored, drew current from the main battery, melted wires in the engine bay and melted the lead posts on the 2nd battery, besides making a nice spark show and smoke screen.

 

ok i got it , thanx everyone for the ton of info
this will help me alot when i upgarde my system

 

Just wanted to say that a capacitor can help for really monstrous bass even if you have a HUGE battery because:

1. The capacitor has close to 0 internal resistance and therefore can respond much more quickly to changes in current demand than a battery which has internal resistance. This allows for quicker bass response. The alternator is actually supplying the power when the car is running so this may not be too big an issue for the battery if you have a sufficiently large alternator.

2. When you run wire over long distances (from front of car to back of car where subs are) there is a voltage drop due to the resistance of the wire. With a heavy load on the wire you have a much larger voltage drop. You can reduce this voltage drop by using larger, higher quality wire which has less resistance but you can run into issues of practicality. The capacitor is usually put really close to the amp so it can make up for the voltage drop under brief heavy loads (a heavy guage very short piece of wire between the cap and amp should have much less voltage drop).


Just remember that a cap stores a very small amount of energy. It just can unload that energy very quickly so it is only good to provide power for a very short burst. It does not make up for grossly undersized wire/alternator/battery.

Edit: Also the very rapid charge/discharge cycles of smaller caps can be used to filter out specific ranges of frequencies so you will see them in use in crossovers. Crossovers are essentially a combination of high-pass and low pass filters.