Capacitors - What for?

[fenderbender]

What do capacitors actually do? Is it really a must if you have external power amplifiers? Aren't power amplifiers a "Plug and Play" thing?

[yebo]

i suppose you are asking why there are capacitors usually connected in parallel to the power supply going to your amp? tama ba assumption ko?

well, capacitors are also called "filters", depending on its use. since the power in a car (or any vehicle) is supplied by an alternator (another word for generator) the wave form of the DC power is half-sinusoidal. that means it follows a sine curve, but all positive (as against a full sinusoidal wave of an AC current which has positive and negative values). since the value of the electric current alternates from a peak that can go as high as 18 volts and a low of zero volts, there is what is called "noise" in the power supply.

note: if 18 volts surprises you, forget the "12 volts" rating. the battery in your car actually is 13.6 volts. the alternator in fact has a "mean" or average voltage output of 15.6 volts because that is the voltage required to charge your battery.

now the amplifier (or any head unit for that matter, and all electronic gadgets in your car) already has a capacitor in the power input terminals called the power capacitor. this is suppose to filter the "noise" that is due to the sinusoidal wave of the power from the alternator. BUT in order to protect the electronics better, they put another bigger capacitor to filter out the "noise", thereby saving your electronic gadgets in your vehicle from damage should the small capacitor inside fail. mas mura kasi maglagay ng capacitor kesa bumili ng amp.

[afrasay]

it also serves as a power reserve as it stores electrical current.

[ssaloon]

Knowing this, we want to look at the two applications of capacitors for car audio:

Power Supply Stabilization
Crossovers


Very large capacitors are used for stabilizing the electrical system. As we have seen, a capacitor stores energy. In a system where several electrical devices are competing for power, when an amp starts using power at an inconstant rate (a little here, a little there), head and dash lights begin to dim. This can also affect other amps in the system. Amps have internal capacitors on the other side of their power supply which hold power for those times when it is really needed. However, the power to charge those capacitors has to come from somewhere, and during peak usage, the power is not always available. The result is that the distortion in the music increases slightly: Sound suffers. A capacitor will store the energy, and will give the energy up when it is needed by other components.

Another benefit of the large capacitor, is that as we mentioned, it passes high frequencies. Any electrical noise will be filtered by a capacitor since the noise is AC. In addition, since the capacitor is a large one, then the "high" frequency can actually be pretty low. In this manner, a capacitor helps reduce power supply noise in your audio system. Unfortunately, the larger capacitors are usually polar, meaning that they have a + and - side, and do not work properly when working backwards. The saving grace here is that, even in reverse, there is some capacitance, just not as much as when polarity is respected.

The second use of a capacitor in car audio, is as a crossover. As we've seen earlier, the capacitor (smaller, non polar ones) will pass AC of higher frequencies, and resist lower ones. Bass blockers are one example of this. When capacitors are used along with coils, they form crossover networks, which improve the sound going to a driver, and can make a speaker system sound a lot better. Many component sets have crossovers, which use a capacitor to carry the + signal to the tweeter, and a coil would carry the + signal to the woofer. The negative signals do not need the components, because as long as the capacitor (or coil) are in the circuit somewhere, they will do their job. Without the coil and capacitors, the tweeter would distort badly, the woofer would usually do a really bad job of reproducing the highs, and there would be a nasty peak where the woofer and tweeter overlap.

full article: http://www.mmxpress.com/technical/capacitors.htm

HTH

[tagalnasaabroad]

bigat ang mga explanations..meron na naman akong nasagap na idea sa electrical capacitors and its functions..ano kaya physical hitsura nito..?!

[GlennSter]

ang sagot sa mga nagkukulang na power ay hindi agad capacitor.

para sa sounds lang yan eh.

upgrade the alternator, thats the right thing to do.

[Tiny]

Originally posted by tagalnasaabroad
bigat ang mga explanations..meron na naman akong nasagap na idea sa electrical capacitors and its functions..ano kaya physical hitsura nito..?!

Here's some more info including pics
http://www.howstuffworks.com/capacitor.htm

...and an Audiobahn cap.

[niwde11]

Originally posted by Tiny
Here's some more info including pics
http://www.howstuffworks.com/capacitor.htm

...and an Audiobahn cap.

ang pagkakaalam ko, eto yung capacitor na ginagamit sa mga malalaking amp(usually the one that drives the subwoofer) especially sa competition. medyo kakapusin kasi yung battery sa mga instance na matindi yung bass(very short moment) at yung capacitor ang nagpupunan. like yebo said, filter n sya ng voltage at the same time quick responses sa voltahe drop. HTH.

[empy]

i thought caps were for making your trunk setup look cool :D ;)

[Tiny]

Actually lot's of people don't believe in what caps those size can do, and they do look spankin'