this is based on another thread in the general section, but i figured id move the topic here:

i hate caps. they suck and dont do a damn thing in my experience. they may *slightly* reduce headlight dimming, but they do not add any noticable sound improvement to a system (unless its somatic in nature). they are a bandaid for a deeper problem, and for a little more you can upgrade your battery/alternator, wich is the only way to really solve the problem. it seems as if several people disagree with me on this, so im opening up to persuasion. i want to hear your opinions on this subject, but only if you can do some things for me:

1) you must have evidence of why they helped you. saying "it sounded so much better" doesnt cut it.

2) if at all possible, it would be ideal to have a voltmeter hooked up both before and after the cap install. this does not mean a multimeter that you hooked up once to check things out. also, you have to have been listening to the same program material before and after, and at the same relative amplitude, otherwise this doesnt means anything.

3) you dont talk about how it helped to reduce your headlight dimming. i already know that it can help slightly in this area, im looking for audible results.


im not trying to be an ass, and i really am hoping a lot of people respond to this. im always open to learing somthing new, but from my experience with caps (since 1998 or so), ive never heard a difference in sound, nor have i seen an improvement in STEADY voltage.

anyone care to discuss?

While I do not have any personal experience with a cap, nor do I have any technical information for you, I would tend to agree with your conclussion. Caps are something thought up by car audio manufacturers to make more money.

Case in point... back in the day when my friends and I were big into stereos, a shop convinced a friend of mine to have a cap installed. The shop said it would make his subs hit harder, and take care of his headlight dimming problem. They install it, and we take it for a drive. Well amazingly enough, his subs did hit harder! Got it home and looked things over... they had turned the gain up :rolleyes It did help with the headlight dimming, although they still dimmed slightly. A few months later an upgraded alternator/battery solved that problem for good.

electrically engineer student here. A 1 farad cap to a battery is like a drop of water to the Niagara falls in terms of stored energy. The thing that cap makers say is that they provide the power for sudden demands of power (which they do, sort of). However a battery is much more willing to give up it power that a cap is. For a cap to discard, the voltage has to drop enough for it trigger its energy release. For this reason a cap along will NEVER completely solve dimming lights. Volts drops= light dim, cap discharges, simple as that. As was mentioned earlier, this a bandaid for a bigger problem.

p.s. of course this is all simplied to a much more understandable level, I could get technical if needed, but that is too much work and will lose meaning to less technically inclined people.

thanks guys! i was really hoping to get some pro-cap people in here, speak up everyone! there wont be bashing or flaming, i really want to know what you think.

blmet, you bring up a good point, that while it is thechnically accurate to say that a cap will provide a "burst" of energy, the "burst" is never defined in either time or amperage. does anyone know of a formula for determining such things? like if we had the overall system voltage drop 1 volt lower than that a 1 farad cap, and x amount of amps was being drawn from the system, how long could the cap provide that amount of energy? if we knew that the effectiveness could be better defined. even if it DID work but only for .3 seconds at "x" amps (or somthing), it might still be an improvment for things like kick drums, although that conclusion might be nullified by the fact that the siganl being transduced isnt really putting much of a strain on the electrical system in the first place.

This is a subject that I can relate to:

Caps are used sound quality. Using Caps in a spl situation is not advised, as the response time will not give you proper results.

Using a cap in a sound quality aspect is designed to stiffen the bass response. A cap is not a replacement for a bigger battery, but if used in conjunction, you will get cleaner bass response.

I personally will not compete without a cap. They are a proven addition to any competition situation.

Good luck to ya!

Here is my personal expierence about caps:

I used to have 6 ORION XTR Pro 12's, 3 MTX 2300X amps, and a MTX 4160 on my mids and highs. My electrical system consisted of only a Optima yellow-top, after 2 batteries in 2 weeks I decided I needed something to help out, so I went and bought a 1 Farad cap. To say the least, it didn't help a damn thing, so I bought another one. The two together made a little difference, but nothing major. My SPL score went from 161.2 to 161.4, and my voltage went from 9.0-9.4 to 9.6-9.8, woopty-do!! Now, I decided to make another major change and ditched the 2 caps for a bigger alternator and a second yellow-top. That shit made a difference, my amps cooled better and actually ran at 12.2V instead of the usual 9.4-10.4, my SPL score came up 2 DBs from 161.4 to 163.8, my lights didn't dim anymore, and my the batteries lasted more than a month. In conclusion, the hell with caps and boosters, if you want to make serious power, use serious stuff!! Caps are something that look cool and make the kid down the block think you have something. Get an extra battery and you'll never regret it.

Caps are pretty much worthless imo in car audio. There main functions are to provide a "burst" of energy as you put it since a cap can dump its charge much quicker then a conventional battery can. It can also help even out the ripples and spikes that are normally seen in DC voltage. Some people believe that a cap helps supply the Amp with an even and steady flow of power and this improves over all performance. Which is true to some effect, since the cap will help with the delivery of power when there is a sudden demand for it. Do I use them on my system, nope. Would I advise any of my friends to use them, nope. I'd tell them to put their money where it would be more helpful over all. A good battery and alt.

<technical geek tidbit info>
capacitance is mesured in farads. A 1-farad capacitor can store one coulomb(sp?) of charge at 1 volt. A coulomb is 6.25e18 (6.25 * 10^18) 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.
</technical geek tidbit info>

Ok, maybe I can shed a little light on the situation (I'm a certified Electronics Technology instructor, btw). Capacitance, by definition, is the opposition to change in voltage. This means it will charge or discharge in order to maintain the source voltage. They are basically batteries with a really fast charge/disharge rate. The amount of time to charge/discharge depends on the resistance of the circuit and is calculated using t = RC (t = time constant - time to charge to 63.2% of source voltage or discharge the cap to 36.8% of its charge, R = resistance in ohms, C = capacitance in farads). The charge/discharge curve is logarythmic... it will charge/discharge less and less as time passes. That's why we are only concerned with the first time constant (voltage should never drop more than that anyway). A capacitor will DEFINITELY help when there is a sudden need for more power... bursts of power as was already mentioned. Where the problem lies is when you are continuously putting a constant strain on the battery. The battery provides the voltage to charge the capacitor, so once it is drained the capacitor can only charge to the source (battery) voltage level. Therefore, the alternator needs to be the main source of power and not the battery for a cap to really be effective during constant voltage drains. So yes, an alternator will have more effect than a capictor, but a combination of the two is ideal. Nothing will help brief sudden high current drains (like tight bass hits) like a capacitor. I have a digital 1.5 Farad cap in my setup and I definitely notice a difference in bass hits. Hope this helps some... I can provide more info if needed, but this is starting to get too long.

^^^thanks sd for that!

one question though....if this is true:"1-farad capacitor can hold 1 amp-second of electrons at 1 volt." then if the electrical system were at say 12 volts then would you get 12amp-seconds (or 12 second amps, is that worded right?)? in other words, the cap could provide 12amps worht of power for one second? im terrible at all that math and electricity stuff once it gets beyond fundamental ohms law formulas. :P

edit: sorry i win just posted at the same time, got a comment for you as well:

"Where the problem lies is when you are continuously putting a constant strain on the battery. The battery provides the voltage to charge the capacitor, so once it is drained the capacitor can only charge to the source (battery) voltage level." this is exactly what im after, im trying to quantify exactly how much a cap can help, given such a situation. i would love to hear more of your thoughts, but could you "dumb it down" for me and any other non EE students. :P

excelent post by the way. ;)

>^^^thanks sd for that!
>
>one question though....if this is true:"1-farad capacitor can
>hold 1 amp-second of electrons at 1 volt." then if the
>electrical system were at say 12 volts then would you get
>12amp-seconds (or 12 second amps, is that worded right?)? in
>other words, the cap could provide 12amps worht of power for
>one second? im terrible at all that math and electricity stuff
>once it gets beyond fundamental ohms law formulas. :P
>
>edit: sorry i win just posted at the same time, got a comment
>for you as well:
>
>"Where the problem lies is when you are continuously putting a
>constant strain on the battery. The battery provides the
>voltage to charge the capacitor, so once it is drained the
>capacitor can only charge to the source (battery) voltage
>level." this is exactly what im after, im trying to quantify
>exactly how much a cap can help, given such a situation. i
>would love to hear more of your thoughts, but could you "dumb
>it down" for me and any other non EE students. :P
>
>excelent post by the way. ;)

Charge, voltage and current are all related, but I think you are misinterpetting the relationship. First of all, current is the flow of electricity, voltage is the potental difference of charges that forces current to flow, and charge is the electrical charge of electrons. Now, current (amperage) is the number of electrons that pass through a conductor in one second. The thing is, it takes very little time for a 1F capacitor to discharge, but the current it provide is initially close to infinite, but drops in amperage quickly as it discharges. So it is hard to quantify its effect in numbers. It the power drain is short, the capacitor will provide instant high current flow. Does that help?

>capacitance is mesured in farads. A 1-farad capacitor can
>store one coulomb(sp?) of charge at 1 volt.

One Farad = one coulomb per volt. Hopefully this will clarify. A 1F capacitor with one volt applied to it will store one coulomb of charge. If changed to 12V (and the cap was rated to handle it) the same 1F cap would store 12 coulombs of charge. To store the same amount of charge if you kept the voltage at 1V, you would need a 12F cap (which would be insanely big and i don't think they exist, btw)

>A coulomb is
>6.25e18 (6.25 * 10^18) 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.

Current is not held, but I can't blame you... next time quote your source (http://science.howstuffworks.com/capacitor2.htm) before copying and pasting to try and sound smart, but that is a good site (i've used it for my students... thought i recognized that).


EDIT --- Sorry, didn't mean to sound like a dick.

"The thing is, it takes very little time for a 1F capacitor to discharge, but the current it provide is initially close to infinite, but drops in amperage quickly as it discharges. So it is hard to quantify its effect in numbers. It the power drain is short, the capacitor will provide instant high current flow. Does that help?"

yes, it helps alot! however im too rigid minded to exept that as a final answer, LOL.

"If changed to 12V (and the cap was rated to handle it) the same 1F cap would store 12 coulombs of charge"

can you explain the relationship between "coulumbs of charge" and amperage? they seem to be the same thing, or at least close. is an ampere simply a measure of coulumbs in a time-frame or somthing?

i understand the basic principles of resistance, amperage, voltage, and power, im just pushing myself a little here. i know youre probably thinking that i need to go and read up on this stuff before i post somthing like this, but the interactivity is prefered in this scenario. im too tired now, but i will probably visit the howstuffworks.com link tomorrow evening when i get out of classes.


also, because this is my thread, i ask that you try to keep things civil. if somone copies and pastes somthing that is, in fact, accurate, then i dont see the harm. this is difficult stuff to explain, and sometimes its better to find a source that can explain it more easily. i do see your point, but i think it isnt worth it to make a big deal of it. thanks. ;)

"can you explain the relationship between "coulumbs of charge" and amperage? they seem to be the same thing, or at least close. is an ampere simply a measure of coulumbs in a time-frame or somthing?"

All a coulomb is is the amount of electrical charge an object's electrons have. Electricity is all about the movement of electrons, and all electrons have a small, negative charge. It takes 6.24x10^18 electrons to equal 1 coulomb of charge. Ok, now an ampere (amp) is the measure of electrons moving in a circuit per second. One amp is one coulomb per second; essentially saying that one amp is 6.24x10^18 electrons moving through the circuit per second. Voltage is the electromotive force (EMF) that pushes these electrons through the circuit.

"To store the same amount of charge if you kept the voltage at 1V, you would need a 12F cap (which would be insanely big and i don't think they exist, btw)"

Some companies make 20 Farad caps, and they aren't much bigger than a cylindrical 1 Farad cap... they're usually about the size of an amp. Inside of them however, is MANY small capacitors, depending on the overall size of the cap.

Now my opinion on caps:
If used in conjunction with bigger battery, upgraded wires (power, charging, and grounds), and an high output alternator, then the caps can have an effect on the system as a whole. I don't totally agree on the idea that caps a just marketing scams. They do the main thing the smaller ones are sold for, reducing the amount that the lights dim when the bass hits. What is really needed in this situation though, is upgraded charging system, and battery, not just a 1 farad cap.

What good is a 1 farad, or even 20 farad cap going to do if the alternator is straining to put out it's 80 amps on a system that is drawing more than that continuously?

There's my $0.02... it's late so I may have babbled or gone off on a tangent, I'll check it in the morning.

thanx for the contribution ominous. I think that basically sums it all up.

difference between coulomb of charge and an amp of current is exactly what you stated.. charge per period of time... I think ominous97rs stated it very well.

I used to compete in DB dragracing events a few years back. I had an AUDIO CONTROL SPL meter, a 3,000 dollar one, to help me build and tune my boxes/setup to get max spl. I tested my theroy using this meter. Theory: Caps will not improve spl. I used the same exact volume level, same source frequency, same everything. I hit the same exact spl's with, and without the caps. My setup was 2 Eclipse aluminum cone 15's, in a box ported through the rear deck of my 96 Grand Prix, 2 Directed 1100D's, and 2 1 Farad 24V caps. I had run 2 sets of 4 gauge power wire also. Optima yellow top battery. Caps do help with sudden voltage drops, but only for a split second. Other than that, they are a waste of money. If you need a cap to "stiffen" your bass, then you need to get to the root of that problem. You need to "create" more energy, not just store it for a short time. A proper way to do it is a high output alternator, and a good, deep cycle battery. I actually noticed less dimming lights when i upgraded to the optima yellow top battery..

I don't have a cap for my system, but I do have some smaller caps. For circuits that I've been building, caps helps. I don't know if you guys know, but caps DO filter out distortion(noise) in a DC circuit. I used some on my Op-amp(small amplifier) and made a little speaker, with the help of a cap, it cleared my voice(input for the system) when it came out of the speaker.

All I know is that it works for my circuit.

Currrently a senior at TTU w/ Electrical Engineering with a 2.0GPA:P so maybe i don't know shit...

^^^^agreed, caps do work as great filters for a/c ripple. i think that was mentioned earlier but wasnt really emphasized, so thanks for your input!

Or maybe if the battery has some kind a noise, I bet that cap will filter that noise out!!;) All I know is that cap stores energy and filters DC stuff! Trust me, caps CAN store A LOT of energy. If you don't believe me, charge it up untill it starts getting bigger( don't use no weak 1nF, use bigger ones like 1F) and touch the terminals...}(

I'm not responsible though...

but does this type of "storing" energy work for our systems??? maybe...maybe not...