Capacitor
50 Watt CAFz'r
Joined: May 2006
Posts: 78
Originally Posted by Rrrrolla
Caps are bandaids for poor electrical systems. If your lights are dimming, that's a pretty good indication you need to either upgrade wiring, your alternator, or install a cap. Adding a battery will NOT help keep your voltage at 14V, it will actually place more of a load on your alternator and actually make your lights dim worse. Extra batteries are great for times when the car is off, but when it's on, they are a hinderance because they present a load to the alternator as well. A capacitor will help regulate your alternator voltage to 14V. I guess it depends on what the problem is whether or not a cap will actually help. If the problem is that wiring to your amp is not good enough and voltage is being dropped across your wire, then you need to upgrade your wiring first. You can check this by watching the voltage at your amp dip and watching it at your alternator to see if it's dipping there too. If it's solid at your alternator, you need to upgrade your wiring cause somewhere there is too much resistance between the alternator and the amp. A capacitor will help mask this by reducing current draw spikes through your wiring, effectively flattening out current draw over a longer period of time. Now, if you measure the voltage at your alternator, and it is dipping there too, you really need to either replace your alternator with a higher current alternator (one that can source high current even at low RPM's, these fella's are big and wil most definitly require modifications to your engine bay), OR you can use a cap at the amp side to also help "smoothe out" the current spikes that would otherwise be required of your weak alternator. This will extend the life of your alternator, keep your lights from dimming, and allow your amp to have a more consistant 14V (which of course will increase the amps power capabilities). Why everyone wants to add more batteries is beyond me. If you want a nice solid 12V, and don't care if your voltage fluctuates between 12 and 14V everytime a bass note hits, then add batteries till your hearts content. You'll be replacing alternators every three months though.
Best way to look at it, batteries start your car, alternator provies current to your amp, cap help regulate to 14V from alternator. Turn car off, and it's all batteries, caps won't do much of anything cause a battery has a huge current capability anyways. Crapy thing is though, when the car's off, you only have 12V, which means in an unregulated amp, less voltage at the rails and less power capability, and in a regulated amp, more current draw, and the risk of exceeding current limitations of the amps internal power supply. These concepts only apply to a car playing music with lots of transients like rock or hip hop, not bass race cars playing spl oriented "music"... ie. test tones at full volume render caps uselss.
Hmmm... that's all I got. It's pretty simple really once you understand the theory. I'm an electronics tech, and this same kinda transient supply voltage problem is resolved all the time with big caps in many differnt electronic applications.
Rrrrolla
Best way to look at it, batteries start your car, alternator provies current to your amp, cap help regulate to 14V from alternator. Turn car off, and it's all batteries, caps won't do much of anything cause a battery has a huge current capability anyways. Crapy thing is though, when the car's off, you only have 12V, which means in an unregulated amp, less voltage at the rails and less power capability, and in a regulated amp, more current draw, and the risk of exceeding current limitations of the amps internal power supply. These concepts only apply to a car playing music with lots of transients like rock or hip hop, not bass race cars playing spl oriented "music"... ie. test tones at full volume render caps uselss.
Hmmm... that's all I got. It's pretty simple really once you understand the theory. I'm an electronics tech, and this same kinda transient supply voltage problem is resolved all the time with big caps in many differnt electronic applications.
Rrrrolla
If the alternator can supply the current that the amp demands at any given time, then why would you need a big capacitor? So ya, I do believe they are bandaids. I can't afford a huge alternator though, so I'm happy with a cap. Most people are. Who would want to modify the engine bay of decent car anyways? If a nasty cut requires surgeory to fix it properly, I'd still throw a bandaid on it and call it a day.
So do you disagree with anything else I've said, or just the bandaid analogy? All I meant was that a better option is a bigger alternator designed for this sort of thing, and if your wiring is weak, it should be upgraded as well. If neither of these are possible (and in most cases upgrading wiring is possible and cheap), a cap will certainly help. Does that help clarify things?
So do you disagree with anything else I've said, or just the bandaid analogy? All I meant was that a better option is a bigger alternator designed for this sort of thing, and if your wiring is weak, it should be upgraded as well. If neither of these are possible (and in most cases upgrading wiring is possible and cheap), a cap will certainly help. Does that help clarify things?
Originally Posted by GPGT1
its the bandaid analogy even if i had the highest output alt available for my engine with 0awg wire i'd still keep the cap, its part of healthy system
Caps DO NOT WORK!. Show me measurements of higher voltage and current in a system before and after adding a cap. Show me Oscilloscope plots of higher current and voltage in a system before and after adding a cap. Show me increased power output from an amp before and after. Show me reduced headlight dimming before and after. Can someone who sells these things actually prove to me that they work? I have never seen any data, any measurements, and plots, anything at all that prove that they work.
On the other hand, I have done the calculations, simulated the car systems and have concluded that CAPS just do not have enough storage capacity to do anything that the sellers claim.
Do not simply reply with answers like this:
"They store energy", "they act as filters", "they stiffen the voltage", or "they are used in most power supplies" etc. GIVE me theory, give me calculations, give me NUMBERS of an actual car power system. I want wire resistance, battery internal resistance, alternator output voltage, current capacity and source resistance, capacitor value, charge and discharge times, amp current draw during bass etc. We live in the 21rst century. We live and die by science not by alchemy, snake oil, and black magic. If someone makes a technical claim, the responsability first rests on them to prove it. That is called peer review. I have seen no peer review of anysort that shows that a couple of farad capacitors in a properly working car electrical systems actually do what they claim. If someone proves it I will gladly be your best spokesperson, and give you my almost new PG Titanium 1 Farad cap!
On the other hand, I have done the calculations, simulated the car systems and have concluded that CAPS just do not have enough storage capacity to do anything that the sellers claim.
Do not simply reply with answers like this:
"They store energy", "they act as filters", "they stiffen the voltage", or "they are used in most power supplies" etc. GIVE me theory, give me calculations, give me NUMBERS of an actual car power system. I want wire resistance, battery internal resistance, alternator output voltage, current capacity and source resistance, capacitor value, charge and discharge times, amp current draw during bass etc. We live in the 21rst century. We live and die by science not by alchemy, snake oil, and black magic. If someone makes a technical claim, the responsability first rests on them to prove it. That is called peer review. I have seen no peer review of anysort that shows that a couple of farad capacitors in a properly working car electrical systems actually do what they claim. If someone proves it I will gladly be your best spokesperson, and give you my almost new PG Titanium 1 Farad cap!
50 Watt CAFz'r
Joined: May 2006
Posts: 78
"They store energy", "they act as filters", "they stiffen the voltage", or "they are used in most power supplies" etc.
This thread has been very entertaining reading for quite some time now. I was trying to stay out of it, but i think i need to add my opinion. (everybodys got one)
I've treid my system with and without caps and it definately sounds better with the caps. I have a 1 and a 2 farad. The amps i run are all the same, 6 pioneer 5100T's.
2-CVR15's, with a bridged amp on each, 380 wrms each
Kicker 2 way crossover between the subs and 6x9's
2-4 way 6x9's with a bridged amp on each, 380 wrms each
2 6" components with a 2 ch amp for each set, 125x2 wrms each
Pheonix gold crossover for the component's
I wanted all the amps to match because with the same amount of gain on each, the volume control tracks properly and i don't have to tweak every time i turm it up. A monoblock amp may not need the caps because it has a beefier power supply. The idea of caps is to stop the voltage from droping during times of high current draw. The cap charges back up in between bass beats and discharges during bass beats when you need current.
Oh yeah, the 2 caps were 68 and 79 dollars. and they work.
An optima battery is about 3-400?? and a custom high output alt can't be any more than about 5-600??
I'll stick with the caps, thanx.
I've treid my system with and without caps and it definately sounds better with the caps. I have a 1 and a 2 farad. The amps i run are all the same, 6 pioneer 5100T's.
2-CVR15's, with a bridged amp on each, 380 wrms each
Kicker 2 way crossover between the subs and 6x9's
2-4 way 6x9's with a bridged amp on each, 380 wrms each
2 6" components with a 2 ch amp for each set, 125x2 wrms each
Pheonix gold crossover for the component's
I wanted all the amps to match because with the same amount of gain on each, the volume control tracks properly and i don't have to tweak every time i turm it up. A monoblock amp may not need the caps because it has a beefier power supply. The idea of caps is to stop the voltage from droping during times of high current draw. The cap charges back up in between bass beats and discharges during bass beats when you need current.
Oh yeah, the 2 caps were 68 and 79 dollars. and they work.
An optima battery is about 3-400?? and a custom high output alt can't be any more than about 5-600??
I'll stick with the caps, thanx.
Originally Posted by Dukk
A capacitor applied correctly does what it is supposed to do. The problem is when people expect capacitors to perform miracles they were not designed to execute.. 
You pick one car over another because it has a bigger engine measured in liters, or because it has more power, measured in HP, or because it accelerates faster, measured in seconds to 60mph. You buy a car amp because it has more watts than another etc.
If you want to pick between 2 cold air intake systems: one manufacturer claims "Get more power" but does not say how much, and in what engine, and the other claims "Increases HP from 185 to 195 at 4500rpm on car engine model XYZ, as tested by certified test lab ABC"
Which would you pick? The one that has proven numbers.
Members of this board regularly trash cheap amps whose written specs claim high power output when we know they are bogus. So why do you believe that caps do anything when there are no spec at all to support the claim?
So why are you putting caps in audio systems when no one shows any numbers and proof that they do anything?
So, how do you measure what a cap is doing?. Sure the spec says 1 Farad, but what does 1 Farad do in a car? Does it keep the voltage from going too low?. By how many volts? For how long? With what current draw? Does it reduce the power supply noise? By how much? Under what conditions? No company can tell me this with examples from a typical car audio setup and car power system.
So, since no company that is making or selling capacitors for car audio use can actually tell me what the product is supposed to do, using measurements that can be verified, I am going to remain very skeptical. I will be happy to change my mind when someone actually proves that they work.
Guys, do not get angry at me. I am trying to shake things up a little, to put a bit of skeptisism in your minds, so that you ask the right questions when companies make all sorts of claims without backing them up.
Last edited by zoomer; May 24, 2006 at 07:08 AM.
Originally Posted by GPGT1
Caps were originally used in powersupplies to smooth out rectified DC current. Then they found that in amplifiers adding more capacitance helps in moments of high output. They're not supposed to be filters. I'm sure most people here know what a sin wave looks like well the DC draw for your AC wave (sound signal) looks the exact same except for the dc draw instead of sloping down into neg voltage it swings right back up. so to draw looks like a bunch of bumps. The capacitor smooths out those bumbs so you have a more constant source. its backwards of what a computer supply does. The cap is not supposed to add voltage or amperage, only hold what you already have for a moment. your power supply still needs to match your draw or the cap wont be as effective. You can see this kind of thing on a scope easily, you have to measure your output with and without the cap and compare. now lets say we had a perfect environment A 700watts rms amp and 700watts DC power supply, your really looking at 1000watts of peak AC power but you dont have 1000watts to feed it thats where the caps come in they have the extra capacity and get to charge in between peak cycles
When I have time, I will post some graphs of waveforms etc.
