| capacitor question - Click HERE for Original Thread |
| night_font |
hi, ok well this is what i have and what is going on.
this is in my prelude
i have a 4guage power wire going to my alpine pdx-1.1000 amplifier which is powering 2 10" type r alpine subs. and my light dim very much when i have the bass going loud and i was told that i should get a car audio capacitor but i don't know what i should get in size i heard of 1.0 farad to 20 farad caps. what size should i get to compensate for the loss in power and not the burn out my alternator.??? thanks. |
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| platnum accord |
cap = pointless.
here is the arguement most people make.
a cap stores lots of current just so it can discharge fast.
in al reality the cap can charge as fast as it can drain, so while its draining its trying to recharge fast therefore shifting the drain time by a small amount of time.
the bigger the farad rating of the capacitor the more it can store, but as it drains it needs to recharge also.
the proper way to go about running a more powerful amp properly in a car would be to first upgrade the battery in your car. that is where the largest gain in "Stock" voltage would be. after that upgrading the main lines under the hood would be next.
The big 3 as its called is when you replace the bat - to frame ground. next would be from the engine to the frame. then after that from the output of the alt to the + of the battery.
this will help charging voltage and is 10000000% necessary if you buy a bigger alt then your stock one.
Next step to stop dimming would be to get a High Output alternator. there are meny companies to choose from but the main choice should be when you pound your system. if you rarely pound during idle then at idle amperage should not matter. if you pump while driving look for a decent output above 1500rpm.
these are all the steps you should take in properly upgrading your electrical system. the order should not really change but if you do more then one you will really notice a difference.
*there may be meny spelling mistakes in here and if someone wants to read over and point out any errors in it feel free to, then maybe this should be stickied so that anyone else who asks this question, has been meny times, the answer will be there for them* |
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| platnum accord |
i have only a 1500Wrms amp. i can run my car with none of my accessories on and i get no dimming. btw i have a 200amp dom iraggi h/o alt, 00guage welding wire for my big 3, and 00 guage running from my group 35 red top to the amp.
if i pump my system with my rear defrost, headlights and ac on, as well as the car running... i get very minimal dimming. only on notes under 25hz seem to make the dimming bad. but other then that, its all good. my h/o alt was around 300 bucks from dom's ebay store. my 00guage wire was under 100 from princess auto. and the battery was around 150 from costco.
and these are all supporting mods you will never hear. |
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| Dan_Gyoba |
I hear people claiming that a cap helps, and it sort of does. I'm sure that the guys with the fugly dB dragsters wouldn't put 'em in if they did nothing, however...
A cap will help WITH THE SOUND. It provides better power regulation to the amplifiers, and "faster" current, overcoming the inherent inductance in any length of wire.
Lights dimming means that you're drawing enough power to drop the voltage. This is a problem, no matter how you cut it. (Yes, even if it's only momentary with the bass notes.)
A capacitor in that case is like a band-aid for a bullet hole. It's not going to do any appreciable good.
Step one is to upgrade the battery. A good (or even just a new) battery is a lot more tolerant of those loads. The little bit of dimming with the bass notes can often be solved with a simple battery upgrade. (I also added a cap at this point, but that was for the SOUND, not the electrical system.) At this point it's also highly recommended to make sure that your ground wire is at least as good as your amp power wire.
If that's inadequate, then the next step is to upgrade the charging system. This will start cutting into your engine power, and is where I draw the line. Enough is enough. I don't need to be setting off car alarms a block away, I can turn it down. |
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| platnum accord |
wire length plays as much a part of voltage drop as wire guage.
think of it like a straw representing a single flow. you cant pull alot through a single straw, but you can pull alot through like 10 straws though. now think of a straw as a single strand of copper wire in an entire cable. the more area to pull from, the better the flow. |
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| white99GT |
| As far as I know (just getting back into this stuff after many, many years) db drag vehicles and all out SPL competitors benefit from huge capacitance for 'burps' and not sustained output. |
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| platnum accord |
they also have a huge battery bank to back up the massive caps.
the main front runner that i have seen doing good for car audio is (spelling may be off) xstatic battcap.
link
http://www.batcap.net/8400.html |
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| Dan_Gyoba |
Yes, wire guage plays a part in voltage drop to amps. (though not at the car's electrical system.) This is evident. However, there is an additional problem that cannot be overcome with any gauge of wire, and that's parasitic inductance. Run 14' of any wire at all, and it will have a measurable inductance. Inductance provides resistance to AC signal, which means that the amplifier will have more trouble with loads that change quickly. Since this is the nature of most music, this inductance poses a problem.
All amplifiers will have capacitors in the PSU to help with this, however, a bit more, particularly for longer power runs will give an advantage to the amplifiers in dealing with these transient loads. This is how a capacitor helps the SOUND of the amplifier. By installing the capacitor across the load, it "smooths" the electrical system load in a manner that reduces the resistance offered by the parasitic inductance in the power wire. By doing so, you ensure that your amplifiers get a more constant voltage, which reduces it's tendancy to clip at high signal peaks.
As I said, the cap is there to help the amplifier. Not the car's electrical system. |
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| platnum accord |
so you go from talking about voltage drop, to ac current? (this is the output of the amp) back to how caps are in amps to how it smooths the load.
tell me how fast a cap discharges as opposed to its rate of charge? |
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| Dan_Gyoba |
I never said that a cap would help the lights dimming. It does help with voltage supply drop at the amplifier.
Because the amplifier's demands for current vary with the music being played, there is a high frequency AC signal superimposed on the DC draw from the battery. This is at the INPUT, because the amp needs to draw more current when the notes hit hard, and less when it does not. The parasitic inductance on the power line makes the sudden demand harder to satisfy. When the current demand suddenly ramps up, and your amp wants that power the most, the power line, regardless of size, increases its resistance.
Conversely, at the end of the peak load, the current in the power line still wants to flow, resulting is a slight voltage spike, though since it's mild, this isn't the problem.
The capacitor provides a means to overcome that inductance, which keeps the voltage at the amp's power supply higher for the first few miliseconds when the demand ramps up. This allows the power line a bit more time (which it needs due to its inductance) to increase it's supply.
So yes, adding a capacitor helps the sound, which is what I said all along. It does not help with the lights dimming, which I never said that it would.
Edit: A capacitor charges and discharges very quickly. It's actual speed varies with the electrolyte involved, the total value of the capacitor in farads, and the voltage applied. It should be able to discharge as quickly as it charges, though this is, of course, dependant on the load presented to it. A charged capacitor with no load can keep it's stored voltage for days. Short the leads, and it can discharge about as fast as the wire can carry the current.
A 1 farad capacitor will charge to the supplied voltage in 1 second at one amp. Discharge would be subject to a falling voltage rate, and so would take longer, but before that point, the rates would be similar.
Since, however, the capacitor should NEVER discharge to a voltage that is appreciably lower than the supply, it's relatively small amount of current capacity is never a problem. The supply current still provides the needed amperage. The capacitor is only there to provide a little buffer. |
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| platnum accord |
just checking because i have herd some car audio fools rant and rave to the death that a cap can discharge faster then it can charge and thats the one and only reason why it is better to do this mod then a battery.
just checking. sorry if it sounded like i was being a dick.
and yeah a cap only buffers for that one little second to slow the draw on the cars electrical system a bit, i still think its a useless piece of equipment, and if it only helps for a few why have it? |
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| Dan_Gyoba |
Yeah, I hear those fools too.
Because the cap does that buffering, it does make a noticeable, and measurable difference in the sound.
While I've heard it argued that some "vast" improvements in sound cannot be measured on equipment, I've always found that an improvement that CAN be measured is an improvement that I can believe in. The improvement that a cap makes in the sound when there is a long power cable involved is both measureable and audible.
Most of the on-line guidelines seem to deal with amplifier power, something like 1F per 1kW amplifier power was the number being bandied about, last I heard.
Probably this is okay as a rule of thumb, and it probably won't hurt.
I go by slightly different methods.
0.05F per 10A of the recommended fuse size on the amplifier as a basis, then multiply by the length of the power cable in meters. If your total is less than 1F then don't bother. The built-in capacitors for the amp power supply will do the job.
For example, my old setup, I had 2 amps, which had a total fuse value of 70A. That gives me a base of 0.35F. I was feeding those amps with 3.5m or 4AWG wire, which gives me a calculated value of 1.225F. My stiffening cap is a 1.2F.
This is overkill considering that my total (RMS) wattage for the system was about 350, but I found it to actually be a good match.
My new amplifiers (still in the boxes) have a total fuse value of 120A, and I'll be feeding them with about 3m of 1/0. I then come up with 1.8F for a cap value, so my existing cap may be a bit weak.
Because the capacitor's job is to overcome the inductance in the power wire, the length of the wire, and the current that it has to flow are the values that I use to determine the needed cap value. It works for me. |
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| platnum accord |
| haha, my 1 amp has a higher draw then that. 200amp alt ftw. |
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| Ravendarat |
| OK my turn to chime in on this one. If you are having constant dimming when playing your system and moderate to loud volumes than you really only have a couple of usefull courses of action. The first one that should be done is a high output alternator. Alot of people dont like using this as a recomendation because its expensive compared to adding in bandaids like caps, but look at it this way. If your car cannot currently charge your system, than how is adding more electrical components really gonna help. Alt First. And when you do that you need a couple wire upgrades. You need to upgrade the power wire from your alt to the battery to accomidate the new upgraded charging system. You should also be upgrading the grounds from the battery to chassis and motor to chassis. Second upgrade is to change to a better quality battery than the stock. A higher capacity battery will help if you are playing the stereo for long periods of time with the motor off or with the motor at idle. The slower the alt spins the less power it produces so the storage is nice to have. At this point in time if you have done these simple upgrades correctly you should not have a power draw issue anymore unless you are running REALLY high power amplifiers, in which case then we need to start talking about dual alt setups, battery banks and so forth. I basically dont talk about caps unless we are talking SPL competitions. |
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| Dan_Gyoba |
quote:
Originally posted by platnum accord
haha, my 1 amp has a higher draw then that. 200amp alt ftw.
Higher draw than that. ;)
I'm not looking for big power though. The 131dB that my old system hit was more than enough for anything that I'm going to listen to. The new system will have a fair amount more power, but I'll never push the new amps.
@Ravendarat: I have a cap, for the simple reason that installing it made an audible improvement in sound quality for me. I wanted (and got) nice tight, accurate bass. The bass is still able to reach deep, but the important thing to me is that it hits fast, and when it's supposed to.
The whole point that I've been making here is that caps are not, and never will be something to prevent voltage drops from excessive load. |
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| gab |
i find that if i do my hair nice i don't need a cap.
so just make sure that you car has nice hair. |
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| Ravendarat |
| Im sorry Dan, I just cant buy that one. I have been doing this for the better part of a decade and have never heard a system that benifited from a cap in a sound quality sense. I have seen banks of them help in SPL numbers but not ONCE have I heard an improvment in the SQ catagory and thats comming from someone who competed in sq for a few years. I think this is a case of psycho-acoustics. If I saw an improvment on a term lab I would by it and say that I must just not hear it, but my ears as it stands are pretty damn good and I am usually the one that points out sound imperfections to others not the opposite. |
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| Dan_Gyoba |
I guess we'll agree to disagree then.
I am well aware of the placebo effect in audio. I've had a good laugh at 'audiophiles' who swear that their $300 power cord for their amplifier made 'a dramatic difference' in their listening room.
I did hear a difference, and it's one that I could repeatably measure with a studio mic and some audio software.
It's not a lot of difference, I'll grant, but it did bring more snap into the drums and some additional definition to the bass guitar notes. With the cap, it sounds more like my home system.
I've also competed in SQ, and built systems for other people who've competed. Some of these systems had a cap, some of them didn't. It also may very well depend on the amplifiers installed as well. Some of them may not have adequate stiffening of their own. |
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| gab |
| i've been doing systems since before stiffening caps were even introduced. and i still need a haircut!! if anything, i'd say a cap makes an install look cool. but unless you are wicked pounding on it, the caps in the amp would more than suffice with proper power/ground/charging system. |
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| platnum accord |
quote:
Originally posted by Dan_Gyoba
Higher draw than that. ;)
I'm not looking for big power though. The 131dB that my old system hit was more than enough for anything that I'm going to listen to. The new system will have a fair amount more power, but I'll never push the new amps.
@Ravendarat: I have a cap, for the simple reason that installing it made an audible improvement in sound quality for me. I wanted (and got) nice tight, accurate bass. The bass is still able to reach deep, but the important thing to me is that it hits fast, and when it's supposed to.
The whole point that I've been making here is that caps are not, and never will be something to prevent voltage drops from excessive load.
ok grammer and spelling nazi.
lol my current setup does around ~130 at 21hz. |
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