rookie question, caps

Not that I've heard of. Then again, I've always heard it was better to run a new battery insted of a cap.

yes...... caps will go bad, its basically a battery with a quick recovery time.

and no they really dont work(as good as a strong electrical system), but they do look cool

(spelling disclaimer: I am typing this quickly, and there is no spellcheck )

Capacitors can go bad, when they do generally it will "bulge" or possibley ooze or smell.

As for whether they work or not has to do with a lot of varibles. The biggest one is the type of power supply your amplifier uses. Most car audio amps use an "unregulated" power supply. These types of amps performance is directly proportionate to the incoming voltage. Wattage = Voltage * Amprage.

So let's say your car is running, putting out 14.4V. That means a 100 amp pulls about 7 amps or current (mind you this is very general as there is some resistence in the wire, and there is a lot of loss in heat at the amp). With that in mind, lets say you have the headlights on, heater on, rolling your power windows up and down....... you may not be at 14.4 let's say you are at 12 volts. You then need a little over 8 amps to output the same power. Make sense so far?

OK, think of your battery as a "barrel of water", and your alternator as a "hose" contantly filling the barrel. Your voltage regulator is like a float valve, so when the barrel is full it slows the flow as not to "overfill" the barrel. Now at the bottom of the barrel is a hole, and the size of this hole varies bases on what all is running in the car. The more stuff on (pulling current, amprage) the bigger the hole. From the factory this is balanced in such a way that you should never empy the barrel in normal use. Generally in a car the headlights are the largest draw. Most decent size audio amps can pull as much as the headlights and a lot of time more. So now what happens is your barrel can not stay full. This is why a larger alternator is critical in a large audio system. Without it, your "barrel" can not refill if you drive around at full volume 24/7.

So where do caps fit in you ask? Well amplifiers have the ability to respond very fast (trasient response time) as things can happen quickly in music. They can respond much quicker than you battery can discharge, especially when loaded down with all the other draws you car is pulling (headlights, heater.....). The cap is not a "battery" per se. It can hold energy that can be discharged (and recharged) at a much higher rate than the battery can. So when you all of a sudden get a huge bass note, the amp can "steel" the extra power needed to be able to play that note, and still be able to control the speaker with out having to wait to "steel" some juice from the headlights (ever wonder why the headlights dim on a bass note).

So for most mid to larger size car amps, yes caps do work. Can they replace a larger alternator, no.


VRISTANG, where are you at in Seattle?

long post

vristang said:

What do you mean they don't work?

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copied from audio forum:
As you may know, amplifiers are made up a bank of little capacitors, resistors, etc. What has been common engineering knowledge is that capacitors store energy, and more or bigger ones assist in balancing the power supply
As you may know, Richard Clark is one of the founders of autosound2000 Tech Briefs, Carsound magazine, and a published author of the industry of mobile electronics. Wayne Harris was previously a leader at Rockford Fosgate in their development.
Wayne came up with the idea of putting several dozen 'little' (approx 100uF) capacitors on a circuit board to 'extend' the power supplies storage. At about the same time, or shortly afterward, Richard came up with the idea of one huge mondo capacitor (I believe it was 800,000uF or 0.8F) to do the job.
Eventually, Richard won. The large cylindrical tubes won over the complicated 48 caps strapped to a circuit board. However, what did this really accomplish?
The number 1 reason would have to be because their lights dim when their
system is playing HARD. In car audio, we are told that a capacitor is
designed to prevent the voltage drop associated with your lights dimming.
The number2 reason is that it is rumored to 'improve' sound quality or
'stiffen' the power supply/source.
HOW MUCH POWER DOES A CAPACITOR STORE?

1 Farad = 100 joules or 100W/second
850cca battery = ~2,200,000 farads

Due to its impedence (ESR & ESL), a cap's energy is only 50% available. What's worse, is that in order for a 1 Farad cap to discharge, first the alternator output must have maxed out, and the voltage must have dropped around 1.5 volts. But I thought a cap was supposed to prevent that (voltage drop)!!!!!????? Yep, you got the point.
My question exactly.
Marketing is the reason why people buy caps. In many cases, upgrading wiring will help your system get the maximum transfer of current. Once that has been reached, adding a capacitor may have a minor effect on your system. 50W over the course of a second is not a lot of power considering an amplifier may draw 2000W to put out 1400 watts.
Also, Once a cap is discharged, where does it get it's power from? The alternator, which is already overloaded. Once a cap is discharged, it's worthless. Like SWEZ says, ・.The cap already shot its wad, an does limp til recharged
SO, WHAT IS A CAPACITOR GOOD FOR?

1. Audio Jewelry- impress chicks with large cylindrical shiny thingy
2. Extra weight in winter time
3. A very POOR... BUT expensive distribution block
4. A projectile in the event of a crash
5. Rolling pin--for cooking purposes
6. A neat thing to tell your friend, "..Hey man, lick the top of this
HOW CAN CAPACITORS IMPROVE SOUND QUALITY?

They can't. Sound quality is not dependant upon the presence of large bulky 1 Farad capacitors. How many 1 Farad Capacitors do you think the Boston Pops, Aerosmith, or Snoop dog use in the recording studio?
When Richard, our fearless inventor, became World renown for winning every competition under the sun, people began copying what he did. Soon, every 'serious' competitor had a 'stiffening' capacitor--not to be confused with the 'loosening' capacitor.
Phoenix Gold's marketing guru had just posted information on how their Powercore (basically the Alumapro CAP15 in a Phoenix shell) had both stabilized their voltage and improved the sound quality. Richard called him on it (all in another post) and the marketing geek was unable to quantify any of the conditions that resulted in the voltage being HELD at 14.2V and the 'improved' sound quality
In a final note, Richard relayed a quote regarding battcaps ( www.battcap.net ) as, "..The audio industry is the only place i know of where you can publish specs that show your product is useless and still be able to sell them------and whats worse is that technically ignorant people will argue against the math!!!!!!!..............RC.." when referring to the product. This also relates to most digital readout capacitors, and I wish my Archie Bunker skills could have said it better myself.



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vristang said:

It has been my understanding that caps drain faster and recharge faster than any battery could ever dream of. This is their function. The battery is still another buffer between the caps and the alt. With these buffers in place (both the battery and the caps) and fully functional, the peak, instantaneous loads placed on the alt will be minimized and averaged over time. Not only are peak loads on the alt reduced, but power available to the amp is maintained at a higher level. This makes sense to me. ???

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Not sure if I was confusing, or if you are responding to iskwezm. But, yes this is basically what I was saying.

vristang said:

I have never heard anyone claim that a cap would improve sound QUALITY.

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Since most amps power supply is un-regulated, any time the votage drops, so does the performance of the amp. Think about the headlights, when the voltage drops, the headlights performance drops. So does the amps. Sound quality is in the whole range of the music including the bass. When voltage is low, the amp can not control the starting and stopping of the sub makeing the bass less accurate. This also effect the rest of the amps as well, but the amps that power higher frequencies do not have the huge current variences that the sub amp will. To give you an idea of amp power in retaltion to sound quality, Velodyne (who arguably builds the best home subs you can buy) has an active servo system on their highest two lines of subs. Both of these series have 3000 watt amplifiers. Of that 3000 watts, 40% of the power is used to "stop" and to "control" the woofer, while the other 60% is to get it moving.


As for the quote from the "audio forum", just like most forums there are varing opinions about everything, and generally boths side can put up a good case. That's what can make a great debate.
In that quote, it mentions both Richard Clark and Wayne Harris. Wayne was very instumental is getting car audio to where it is today, and definatly one of the most intelligent guys on amplifiers there is. He designed most of all the early RF stuff, and when he is putting caps in line between the amps and the battery you can be sure he did it for performance and not marketing. Also, Richard Clark was running caps when he was competing in amatuer back when SpeakerWorks did his car in the late 80's. They were way ahead of thier time then. They were using things like caps, aperiotic membranes, and using commercial commpression drivers connected to custom horns under the dash to get equal distant positioning in the car for improved imaging. Again, this was in the late '80's. They kept all this stuff very secret until Richard and David Navone started Autosound 2000. If memory serves me correct this was about in 1990 or so.

Where this qoute loses it's credibility (in my opinion) is when the author says:

How many 1 Farad Capacitors do you think the Boston Pops, Aerosmith, or Snoop dog use in the recording studio?

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Yes, they do not use any kind of cap in a recording studio or at a concert, or in any home audio system. Why? No voltage or current issues. When was the last time your home subwoofer hit and your lights dimmed? Or at a concert and the bass was hitting so hard the light show went out? Or a nightclub? If you have 110 volts in a house, then to get a 100watts you only pull 1 amp, compared to the 7 amps needed at 14.4V or over 8 amps at 12.5V in the car. So a 1000 watt home system fully rocking still only pulls about 9 amps of current. You can not compare home and car because of the electical system in a car.

vristang said:

The whole reason I posted the question in the first place was in hopes of diagnosing a problem that I have. After about 10s of running the sound system, everything but the 8s will shut off. No 15s and no front end. Power does not come back, so I can rule out an intermittent short. I did not do the install, so I am not sure how all the wiring was run, but I am fairly certain that the Picasso and 10.0 are running off the caps and that the Reference amp is not.

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Well sounds like you may have multilple things going on. If it was an all voltgage issue, the system would stay on at lower volumes and not shut off as well. Also, you could have an intermitent short, as some amps once they go into protection will not come back on until they are power cycled.

The first thing I would do is to get your batteries load tested. This will tell you if they are any good still or not. Any place that sells batteries should do this at N/C. Also, remember never replace only one battery in a muti-battery system. Batteries will sink to the lowest common point. So one bad battery will drag them all down to it's level. I have a stong suspition this is your problem. Also be sure to have your charging system tested to make sure your alternator is still putting out. Those large 160amp alternators put out a lot of heat, and it is not uncommon to have issues with them, like any other high performance item with moving parts.

If they test OK, and the alternator is fine, then make sure all batteries are fully charged, then disconnect each amp (pull the fuse). Put the fuse for the high end amp back in first to see if it plays for longer than the 10 seconds. If it does, you probably do not have a problem there. If it does shut off, you probably have a short (blown speaker, bad crossover, pinched wire....)

Once you get that one working fine, pull the fuse again and move on to the amp that powers the 8" and repeat.

Hope this helps.

Whole lotta reading in this thread.
Anyways, I think you have a wiring issue, and based off what you said I'd start with the grounds, turnon lead, power line and then the rest of the wiring.