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#1
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when is capacitors used?
I heard that the car battery cannot supply current at a fast enough rate
(because of chemical reaction neccesary) for subwoofers and that a cap is needed. At what power ratings should one start to worry about this? |
#2
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when is capacitors used?
Most of the people here will tell you that you never have to worry
about a cap, since it is useless - I do not completely agree with that though. If you have a power problem, invest your money into a better electrical system (battery/alternator). My opinion is that if your light on the car dim a bit on deep bass tone, a cap will fix this problem. I bought one to fix this and I see no diming anymore; it also look cool. The way you asked the question, it sounds like you do not know if you need one. If you don't know if you need one, you probably don't. Andre. "Johan Wagener" wrote in message ... I heard that the car battery cannot supply current at a fast enough rate (because of chemical reaction neccesary) for subwoofers and that a cap is needed. At what power ratings should one start to worry about this? |
#3
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when is capacitors used?
I heard that the car battery cannot supply current at a fast enough rate
(because of chemical reaction neccesary) You heard wrong. Current due to electron flow moves at the speed of light. for subwoofers and that a cap is needed. At what power ratings should one start to worry about this? You should start to address whether or not a capacitor will help you if your headlights are dimming such that it's become an annoyance to you. When that happens, consider installing capacitors as close to the headlights as possible. Oftentimes it won't be much more money to buy a high output alternator or have yours modified by a shop. This is a much more effective tool to reduce dimming. |
#4
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when is capacitors used?
On Fri, 19 Dec 2003 11:53:52 -0500, "Mark Zarella"
wrote: I heard that the car battery cannot supply current at a fast enough rate (because of chemical reaction neccesary) You heard wrong. Current due to electron flow moves at the speed of light. You're right, Mark, but it is fair to say that a battery might not be able to "supply current at a fast enough rate" in some instances. If you have a large current draw that the alternator cannot keep up with, and the battery has to make up the difference, you can get a significant voltage drop due to the relatively high internal resistance in the battery. (This is why even a "good" battery will often drop down to as low as 9.6V while starting your car.) for subwoofers and that a cap is needed. At what power ratings should one start to worry about this? You should start to address whether or not a capacitor will help you if your headlights are dimming such that it's become an annoyance to you. When that happens, consider installing capacitors as close to the headlights as possible. Oftentimes it won't be much more money to buy a high output alternator or have yours modified by a shop. This is a much more effective tool to reduce dimming. I would go even further and recommend upgrading the wiring to the headlights before trying a capacitor. And I agree, if you can get a new alternator or get your current one rewound for reasonably little money, that's probably the way to go. Scott Gardner |
#5
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when is capacitors used?
I heard that the car battery cannot supply current at a fast enough
rate (because of chemical reaction neccesary) You heard wrong. Current due to electron flow moves at the speed of light. You're right, Mark, but it is fair to say that a battery might not be able to "supply current at a fast enough rate" in some instances. If you have a large current draw that the alternator cannot keep up with, and the battery has to make up the difference, you can get a significant voltage drop due to the relatively high internal resistance in the battery. (This is why even a "good" battery will often drop down to as low as 9.6V while starting your car.) That's correct. All power sources have an output Z. But that's quite different from what he said. Especially in regard to his next comment. for subwoofers and that a cap is needed. At what power ratings should one start to worry about this? You should start to address whether or not a capacitor will help you if your headlights are dimming such that it's become an annoyance to you. When that happens, consider installing capacitors as close to the headlights as possible. Oftentimes it won't be much more money to buy a high output alternator or have yours modified by a shop. This is a much more effective tool to reduce dimming. I would go even further and recommend upgrading the wiring to the headlights before trying a capacitor. I've demonstrated before (in a post to Eddie Runner about 6 months ago - the math is there in a google search) that the headlight wiring makes no difference. |
#6
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when is capacitors used?
On Sat, 20 Dec 2003 10:17:10 -0500, "Mark Zarella"
wrote: I heard that the car battery cannot supply current at a fast enough rate (because of chemical reaction neccesary) You heard wrong. Current due to electron flow moves at the speed of light. You're right, Mark, but it is fair to say that a battery might not be able to "supply current at a fast enough rate" in some instances. If you have a large current draw that the alternator cannot keep up with, and the battery has to make up the difference, you can get a significant voltage drop due to the relatively high internal resistance in the battery. (This is why even a "good" battery will often drop down to as low as 9.6V while starting your car.) That's correct. All power sources have an output Z. But that's quite different from what he said. Especially in regard to his next comment. for subwoofers and that a cap is needed. At what power ratings should one start to worry about this? You should start to address whether or not a capacitor will help you if your headlights are dimming such that it's become an annoyance to you. When that happens, consider installing capacitors as close to the headlights as possible. Oftentimes it won't be much more money to buy a high output alternator or have yours modified by a shop. This is a much more effective tool to reduce dimming. I would go even further and recommend upgrading the wiring to the headlights before trying a capacitor. I've demonstrated before (in a post to Eddie Runner about 6 months ago - the math is there in a google search) that the headlight wiring makes no difference. True enough. I should have suggested checking the connections and general condition of the wiring rather than using the vague term "upgrading". Ten to fifteen amps of current shouldn't tax the factory wiring, assuming all of the connections are clean. I noticed you suggested placing the capacitors as close to the headlamps as possible. If the headlight wiring makes no difference, than the placement of the caps shouldn't be that critical. If the headlamp wiring is of adequate size that there's not a voltage drop between the battery and the headlamps, then there's no reason to worry about the physical placement of the caps. You could put them in parallel with the battery, at any location in the car, as long as the wiring between the capacitors and headlamps doesn't produce a significant voltage drop with the rated current. I maintain that if placing the caps closer to the headlamps makes a difference, then the existing headlamp wiring has problems. Scott Gardner |
#7
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when is capacitors used?
I would go even further and recommend upgrading the wiring to the
headlights before trying a capacitor. I've demonstrated before (in a post to Eddie Runner about 6 months ago - the math is there in a google search) that the headlight wiring makes no difference. True enough. I should have suggested checking the connections and general condition of the wiring rather than using the vague term "upgrading". Ten to fifteen amps of current shouldn't tax the factory wiring, assuming all of the connections are clean. Dimming isn't a matter of taxing the wiring though. It's the system voltage fluctuation. That's why the resistance of the wire has no bearing on the level of dimming. Just the average power of the headlight output. I noticed you suggested placing the capacitors as close to the headlamps as possible. If the headlight wiring makes no difference, than the placement of the caps shouldn't be that critical. I wouldn't call it critical. If the cap is part of the aesthetics of the installation, then install it wherever. But it's most effective near the device that needs it, as it minimizes the impedance between the cap and the symptomatic device (eg. headlights) while maximizing it elsewhere. Ideally, you'd diode isolate the headlights, but then you have to deal with high current diodes and a diode drop. Placing the cap near the headlights is the second best solution, because the ratio of impedance between cap and headlights and cap and rest of system is maximized in that case, and as a result the currentfrom the cap "preferentially" flows through the headlights. If the headlamp wiring is of adequate size that there's not a voltage drop between the battery and the headlamps, then there's no reason to worry about the physical placement of the caps. But there's always a v drop. The question is how significant it is. Well, if the cap is delivering a large amount of transient current (which is supposedly the point of using them), then the v drop can be substantial. And in fact, it turns out the inductance of the wire may even be more detrimental. You could put them in parallel with the battery, at any location in the car, as long as the wiring between the capacitors and headlamps doesn't produce a significant voltage drop with the rated current. I maintain that if placing the caps closer to the headlamps makes a difference, then the existing headlamp wiring has problems. Neglecting reactance, let's suppose the resistance of the wire from headlight to battery is equal to the resistance of the wire from battery to amp. Then by putting it in parallel with the battery, or even better, on a separate lower impedance wire (right next to the headlights, for instance) the resistance from cap to headlight will be halved (or better). So why does this matter? It's not uncommon for the resistance of the wire from battery to amp to be, say, .01 ohms (about 15ft of 8 gauge, not including connections and imperfections). The resistance from the battery to headlights is probably at least that amount (6ft of 12ga is about .01 ohms). Putting the cap at the amp doubles (at least) the resistance between cap and headlights AND increases the current draw from the cap due to the amp which contributes to the effective v drop due to a faster rate of discharge since the amp draws more current than the headlights. In summary, it's ideal to minimize the resistance between cap and headlights AND maximize resistance between cap and the remainder of the system. Diode isolating the headlights is the extreme of this concept, as the resistance between the cap and the rest of the system approaches infinity. And as I mentioned previously, the inductance of the wire also plays an important role due to the transient nature of the cap discharge, and there's a linear relationship between inductance and wire length - which can get rather long with a typical amplifier power wire. |
#8
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when is capacitors used?
I wouldn't call it critical. If the cap is part of the aesthetics of the
installation, then install it wherever. But it's most effective near the device that needs it, as it minimizes the impedance between the cap and the symptomatic device (eg. headlights) while maximizing it elsewhere. Ideally, you'd diode isolate the headlights, but then you have to deal with high current diodes and a diode drop. Placing the cap near the headlights is the second best solution, because the ratio of impedance between cap and headlights and cap and rest of system is maximized in that case, and as a result the currentfrom the cap "preferentially" flows through the headlights. I find this interesting. Several people on this NG argue that caps do nothing for systems, and that they are only bandaids to a larger problem. Why then would you want to install capacitors at your headlights??? The headlights are not the symptomatic device, the whole cars electrical system is. By installing isolation diodes and caps on your headlights, you're just masking the fact that your whole electrical system is having a large voltage drop. You want the caps to take care of the highest fluctuating load, which in almost all aftermarket stereo situations is going to be your amps. If your headlights are dimming, then your ignition coil is also seeing a voltage drop, as well as your cars ECU (unless you drive an old carbd car ). Take apart your alternator and look at the windings... you think that thin wire and those brushes are meant to handle 75 amp pulses? Truly the best way to do a stereo install, if you've got the $$$ would be to run a sealed cell and a couple capacitors very close to the amps, and then isolate that system with some big ass zener diodes that will keep the current draw constant, or at least below a set amperage. I think it would be safe to say capping the flow from your alternator to 35 continuous amps would be more than enough to sustain most systems with most types of music. I'm not picking on any one person here, but I've been a member of many mailing lists and newsgroups over the years, and I find it funny how quick people are to flame and put down other peoples opinions. This NG seems to be particularly bad for it... Cheers, Aaron |
#9
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when is capacitors used?
I find this interesting. Several people on this NG argue that caps do
nothing for systems, and that they are only bandaids to a larger problem. I think it's mostly reactionary. People make the claim that they're useless mostly because people come in with crazy preconceived notions that they'll do something that they just can't do. Why then would you want to install capacitors at your headlights??? The headlights are not the symptomatic device, the whole cars electrical system is. By installing isolation diodes and caps on your headlights, you're just masking the fact that your whole electrical system is having a large voltage drop. But who cares? The point is that the only *symptom* that you know about is the headlight dimming. If the dimming didn't exist, you'd have no idea there's a voltage drop. So, unless it's severe enough such that it starts messing with the computer or causing your car's RPM to fluctuate at stop lights, it's a "problem" that should be ignored. You want the caps to take care of the highest fluctuating load, which in almost all aftermarket stereo situations is going to be your amps. If your headlights are dimming, then your ignition coil is also seeing a voltage drop, as well as your cars ECU (unless you drive an old carbd car ). Take apart your alternator and look at the windings... you think that thin wire and those brushes are meant to handle 75 amp pulses? Sure they can. Especially the ones in the 135 amp alternator in my Caddy. Truly the best way to do a stereo install, if you've got the $$$ would be to run a sealed cell and a couple capacitors very close to the amps, and then isolate that system with some big ass zener diodes that will keep the current draw constant, or at least below a set amperage. Uh...no. The batteries will be of little use, as their output voltage is too low to deliver a significant amount of current when needed. One good battery should easily do the trick. Capacitors near the amps will do less to reduce dimming than near the headlights. Similarly, capacitors near the amps will do less to reduce the fluctuations at the ECU than installing caps near the ECU itself. The Zener solution that you propose would require some huge zeners, rendering it impractical. If you really wanted to be meticulous about it, you'd begin by installing a badass alternator and a good ol' Diehard battery. Then, you could diode isolate your ECU, headlights, and whatever else you wanted to diode isolate. For those of you reading this who don't know what I mean by diode isolate, I mean installing a capacitor next to the device that you're trying to keep the input voltage constant and isolating this capacitor-device combo with a high-current diode so that the current that the capacitor discharges entirely goes to the device, and not the entire electrical system. I think it would be safe to say capping the flow from your alternator to 35 continuous amps would be more than enough to sustain most systems with most types of music. Why would you want to cap it? I'm not picking on any one person here, but I've been a member of many mailing lists and newsgroups over the years, and I find it funny how quick people are to flame and put down other peoples opinions. This NG seems to be particularly bad for it... I've been involved with many also, and I've never been in a NG where there were so few trolls and such inquisitive posts. Rarely do I see people putting down someone else's opinions (unless it's a Nousaine-Runner debate, or anything that lizzard types), but rational discussion and debate is commonplace. |
#10
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when is capacitors used?
I think it's mostly reactionary. People make the claim that they're useless
mostly because people come in with crazy preconceived notions that they'll do something that they just can't do. Okay, I agree that people have notions that they'll make their ****ty amp work wonders, increase their SPL, etc. And it's good to set them straight so they don't get disappointed when they don't do what they think they'll do, but when I came in here and mentioned my caps worked for me, I got a reaction that everything I said should be taken lightly... |
#11
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when is capacitors used?
I find this interesting. Several people on this NG argue that caps do
nothing for systems, and that they are only bandaids to a larger problem. MOST times that is true. Caps are not a wonder fix it all solution like most people that sing thier praises think they are. Why then would you want to install capacitors at your headlights??? To keep them from dimming. The headlights are not the symptomatic device, the whole cars electrical system is. By installing isolation diodes and caps on your headlights, you're just masking the fact that your whole electrical system is having a large voltage drop. Your really just fixing the only problem you can see. Most likely you couldnt actually HEAR a difference, but you can see one with the headlights. If you put small caps up there then you would NEVER know. As a side note the caps to install up there are cheap, a couple of dollars a peice. Not the $80 dollar giant ones you see in the installs. You want the caps to take care of the highest fluctuating load, which in almost all aftermarket stereo situations is going to be your amp Says who? If your headlights are dimming, then your ignition coil is also seeing a voltage drop, as well as your cars ECU (unless you drive an old carbd car ). And unless its a signifigant voltage drop they likely wont care. AND if you are having that large of a voltage drop then a cap or 2 is NOT the solution. I'm not picking on any one person here, but I've been a member of many mailing lists and newsgroups over the years, and I find it funny how quick people are to flame and put down other peoples opinions. This NG seems to be particularly bad for it... I know I am not "flaming" you. BUT it is not an opinion it is PHYSICS. You came in on SEVERAL posts boasting the need for caps and how they helped your system so much, when they likely did little, and they did that for short transients. There are great discussions on here all the time, but the sales myths will get you busted everytime. Les |
#12
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when is capacitors used?
I think it's mostly reactionary. People make the claim that they're
useless mostly because people come in with crazy preconceived notions that they'll do something that they just can't do. Okay, I agree that people have notions that they'll make their ****ty amp work wonders, increase their SPL, etc. And it's good to set them straight so they don't get disappointed when they don't do what they think they'll do, but when I came in here and mentioned my caps worked for me, I got a reaction that everything I said should be taken lightly... Depends what you said. I read some of what you said, and replied to some of it too. You made claims that are probably right on. I won't doubt your experiences, because I have no reason to suspect you're lying. But it's perfectly reasonable to question your interpretations of your results, and that's what soundfreak, I, and others have done. |
#13
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when is capacitors used?
To keep them from dimming.
If my headlights are dimming it's telling me I have a larger problem. Your really just fixing the only problem you can see. Most likely you couldnt actually HEAR a difference, but you can see one with the headlights. If you put small caps up there then you would NEVER know. As a side note the caps to install up there are cheap, a couple of dollars a peice. Not the $80 dollar giant ones you see in the installs. I would know when I see my volt meter drop, as well as my dash lights dim. I'm not going to mask the fact that my whole electrical system is having a large voltage drop. You want the caps to take care of the highest fluctuating load, which in almost all aftermarket stereo situations is going to be your amp Says who? Me. Can you tell me a load in your system which is going to fluctuate more than the amp??? The headlights are constant, your ignition coil is pretty constant, head unit may fluctuate a few amps but not if your running everything on preouts. The amp may fluctuate from 10 amps up to 70 amps and back again. The only other thing that will draw that much is the starter and I don't tend to use that while I'm driving. And unless its a signifigant voltage drop they likely wont care. AND if you are having that large of a voltage drop then a cap or 2 is NOT the solution. Instead of telling me I'm wrong, tell me what your solution would be. I have a very good battery, and a strong alternator, and good wires and grounds. What should I do next? I know I am not "flaming" you. BUT it is not an opinion it is PHYSICS. You came in on SEVERAL posts boasting the need for caps and how they helped your system so much, when they likely did little, and they did that for short transients. There are great discussions on here all the time, but the sales myths will get you busted everytime. How can you assume whether they did or didn't help my system??? Next time, just for you guys, I'll get before and after SPL numbers just to see. I don't imagine it'd be worth much at full tilt, maybe .5 Db if that on the sustained bass, and nothing for the initial hit. I did however notice a SQ difference, and my personal taste liked it. Aaron |
#14
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when is capacitors used?
Depends what you said. I read some of what you said, and replied to some of
it too. You made claims that are probably right on. I won't doubt your experiences, because I have no reason to suspect you're lying. But it's perfectly reasonable to question your interpretations of your results, and that's what soundfreak, I, and others have done. Sounds good to me. I may have seemed to be claiming more than I was trying to say and that's where we got crossed up. I don't want anyone on this list to think that caps are wonder beasts, but I don't want them to think their useless either. They have their time and place in some setups, and in my situation they did what I bought them for, and that's all I was trying to say. Sorry for the confusion... Aaron |
#15
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when is capacitors used?
Instead of telling me I'm wrong, tell me what your solution would be. I
have a very good battery, and a strong alternator, and good wires and grounds. What should I do next? Check your battery connection again. Check your alternator. Check the fuse connections. If your problem is that severe then something else has to wrong. 2 farads of capacitance are not going to actually SOLVE the problem if its that bad. How can you assume whether they did or didn't help my system??? Because physics doesnt change depending upon the setup. The numbers tell me things. Our ears are easily deceived. Go back though what we talked about and look. The numbers tell me certain things. I dont doubt that you percieved certain things. But you "heard" and felt things that are below the threshold of hearing and touch. Pychoacoustics, study it. Les |
#16
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when is capacitors used?
Says who?
Me. Can you tell me a load in your system which is going to fluctuate more than the amp??? The headlights are constant, your ignition coil is pretty constant, head unit may fluctuate a few amps but not if your running everything on preouts. The amp may fluctuate from 10 amps up to 70 amps and back again. The only other thing that will draw that much is the starter and I don't tend to use that while I'm driving. If you flip the AC on high to off over and over again it'll usually beat your amp. How can you assume whether they did or didn't help my system??? Next time, just for you guys, I'll get before and after SPL numbers just to see. I don't imagine it'd be worth much at full tilt, maybe .5 Db if that on the sustained bass, and nothing for the initial hit. I did however notice a SQ difference, and my personal taste liked it. If you can detect half a dB in a car, then come on by so I can write up a paper on you. |
#17
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when is capacitors used?
Check your battery connection again. Check your alternator. Check the fuse
connections. If your problem is that severe then something else has to wrong. 2 farads of capacitance are not going to actually SOLVE the problem if its that bad. The same system had the same reaction on two seperate cars. Maybe I need to run a dedicated ground or something. Because physics doesnt change depending upon the setup. The numbers tell me things. Our ears are easily deceived. Go back though what we talked about and look. The numbers tell me certain things. I dont doubt that you percieved certain things. But you "heard" and felt things that are below the threshold of hearing and touch. Pychoacoustics, study it. I understand what you're saying, but my main results are not the seat of the pants kind. Before caps my voltmeter (the one in my MR2's dash, as well as a seperate DMM) showed a substantial (1-2 volt) voltage drop at each bass hit. After installing the caps that drop was signifigantly reduced, to the point that I had to TRY to get any drop out of it. I wouldn't try to argue just on a seat of the pants thing... I've heard too many people say their air filter made their car feel faster to try to argue a point like them. Aaron |
#18
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when is capacitors used?
If you flip the AC on high to off over and over again it'll usually beat
your amp. For one thing my A/C would have to work LOL, (I live in Canada, don't need it). And another thing an A/C compressor runs off the belts in my cars. If you can detect half a dB in a car, then come on by so I can write up a paper on you. I was just guessing at the actual amount, like I said I'd like to get a gauge in my car when I buy new caps to see if there is an actual SPL difference. I know what you mean though, in one of my regular lists we constantly get newbs saying they can feel that extra 4 hp that there (insert gimmick part here) gave them, but it's well known that you need at least 10 hp to make any difference that the 'ole seat of the pants dyno could detect. That said I've been a musician for a while and do have pretty sensitive ears, but I know I'm limited by those damn human limits. LOL Aaron |
#19
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when is capacitors used?
If you flip the AC on high to off over and over again it'll usually beat
your amp. For one thing my A/C would have to work LOL, (I live in Canada, don't need it). And another thing an A/C compressor runs off the belts in my cars. So does the alternator. Anyway, the blower runs off the alt. That's why your voltage drops significantly when you turn the fan on. Mine actually goes from 14.6 to 13.3, which seems to me to be a bit excessive actually. If you can detect half a dB in a car, then come on by so I can write up a paper on you. I was just guessing at the actual amount, like I said I'd like to get a gauge in my car when I buy new caps to see if there is an actual SPL difference. I know what you mean though, in one of my regular lists we constantly get newbs saying they can feel that extra 4 hp that there (insert gimmick part here) gave them, but it's well known that you need at least 10 hp to make any difference that the 'ole seat of the pants dyno could detect. That said I've been a musician for a while and do have pretty sensitive ears, but I know I'm limited by those damn human limits. LOL Those pesky brains are always getting in the way! |
#20
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when is capacitors used?
Those pesky brains are always getting in the way!
I'm gonna go drown mine with beer and see if that helps me forget everything I learned in school. Nice talkin to ya... I'll report on any findings, good or bad, when I replace my stolen caps. Too bad I don't have an SPL meter. I do have access to a thermocouple but that's not the important part anyway... |
#21
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when is capacitors used?
I suggest those that really have an issue with dimming headlights. Look at
redoing their Headlight circuit. That would be more benifit to eliminating the dimming issue. -- 1991 Tornado Red Corrado, CCA Member # 6645 Stereo is a continuous W.I.P. There are two parts to wisdom: 1) Having a lot to say, and 2) Not saying it. |
#22
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when is capacitors used?
I understand what you're saying, but my main results are not the seat of
the pants kind. Before caps my voltmeter (the one in my MR2's dash, as well as a seperate DMM) showed a substantial (1-2 volt) voltage drop at each bass hit. After installing the caps that drop was signifigantly reduced, to the point that I had to TRY to get any drop out of it. I wouldn't try to argue just on a seat of the pants thing... I've heard too many people say their air filter made their car feel faster to try to argue a point like them. But what does that voltage drop actually represent in terms of AUDIBLE differences? Not enough for you to hear it. Look at the discussion b/ween Mark and John Durbin, and look at the math and you will see. Good write up by the both of them and informative. Psychoacoustics is more powerful than you think. You saw the change on the DMM and then "heard" one as well. A similar thing happened to me the other day adjusting delay rings in a large Hall. One ring needed more level, I adjusted it in the computer, and I heard a difference. Only when I went back to the comp did I realize I adjusted the wrong ring!!!! It happens. You expect the change so you hear it. Les |
#23
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when is capacitors used?
On Sun, 21 Dec 2003 00:07:11 -0500, "Mark Zarella"
wrote: snip I've been involved with many also, and I've never been in a NG where there were so few trolls and such inquisitive posts. Rarely do I see people putting down someone else's opinions (unless it's a Nousaine-Runner debate, or anything that lizzard types), but rational discussion and debate is commonplace. I'll second this - if you want to be physically sickened, hang out at rec.audio.opinion for a few days. Around here, I like the fact that for he most part, people can disagree without it quickly degenerating into name-calling. Scott Gardner |
#24
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when is capacitors used?
"Mark Zarella" wrote in message ...
I heard that the car battery cannot supply current at a fast enough rate (because of chemical reaction neccesary) You heard wrong. Current due to electron flow moves at the speed of light. for subwoofers and that a cap is needed. At what power ratings should one start to worry about this? You should start to address whether or not a capacitor will help you if your headlights are dimming such that it's become an annoyance to you. When that happens, consider installing capacitors as close to the headlights as possible. Oftentimes it won't be much more money to buy a high output alternator or have yours modified by a shop. This is a much more effective tool to reduce dimming. WHAT?!?!?!?!....ok if ur headlights dim.... that means that its not only the headlights that have the shortage issue its everything sitting on this electric circuit...installing a cap near the headlights will only take care of the headlights....not everything else...the car will still be affected by this lov voltage |
#26
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when is capacitors used?
WHAT?!?!?!?!....ok if ur headlights dim.... that means that its not
only the headlights that have the shortage issue its everything sitting on this electric circuit...installing a cap near the headlights will only take care of the headlights....not everything else...the car will still be affected by this lov voltage Who cares about the rest of the car? What's the fluctuation going to hurt? The only reason the driver even notices that there's a fluctuation is because of dimming. If the fluctuation is so severe that it could potentially cause damage, then more important issues must be addressed. |
#27
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when is capacitors used?
WHAT?!?!?!?!....ok if ur headlights dim.... that means that its not
only the headlights that have the shortage issue its everything sitting on this electric circuit...installing a cap near the headlights will only take care of the headlights....not everything else...the car will still be affected by this lov voltage Well, as Mark said, installing the cap near the headlamps gives the headlamps preference when it comes to using the capacitors output, but the rest of the car's electrical system still sees the benefits of the capacitor. Mark and I cordially disagree on this point, though. I think that if there's enough of a voltage drop between the battery and the headlamps such that you need to put the cap near the headlamps, then the headlamp wiring probably needs some attention. It's not the headlight wiring causing the v drop. It's the entire electrical system. So when capacitors provide high current to the devices, the impedance of the wires (and the impedance of the cap itself) are the only limiting factors, and therefore cannot be neglected. This is based on my installs, where the connection between the battery and the cap (if a cap is even needed) is never less than a 4-gauge wire. This means that there's essentially no voltage drop between the cap and the battery, so if there's a voltage drop between my cap in the trunk and the headlamps under the hood, it's a deficiency with the headlamp wiring. This is where you're mistaken. 12 ft of *perfect* 4 gauge wire is .003 ohms. The inductance is even more critical (much more critical in fact), but the effect can be described with just the resistance. Anyway, the resistance of 5 ft of 12 ga for the headlights is about .008 ohms. So if you install the cap at the amplifier terminals, the impedance presented to it from the amp is much smaller than .011 ohms and therefore all of the current is essentially delivered to the amplifier. Installing it near the headlights makes the impedance from cap to headlights much smaller than the ..011 ohms in the other direction. You can model this with a simple voltage divider circuit putting the cap at different nodes. Maybe I'll put up a website later with the simulations. |
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when is capacitors used?
On Sun, 21 Dec 2003 11:14:06 -0500, "Mark Zarella"
wrote: WHAT?!?!?!?!....ok if ur headlights dim.... that means that its not only the headlights that have the shortage issue its everything sitting on this electric circuit...installing a cap near the headlights will only take care of the headlights....not everything else...the car will still be affected by this lov voltage Well, as Mark said, installing the cap near the headlamps gives the headlamps preference when it comes to using the capacitors output, but the rest of the car's electrical system still sees the benefits of the capacitor. Mark and I cordially disagree on this point, though. I think that if there's enough of a voltage drop between the battery and the headlamps such that you need to put the cap near the headlamps, then the headlamp wiring probably needs some attention. It's not the headlight wiring causing the v drop. It's the entire electrical system. So when capacitors provide high current to the devices, the impedance of the wires (and the impedance of the cap itself) are the only limiting factors, and therefore cannot be neglected. This is based on my installs, where the connection between the battery and the cap (if a cap is even needed) is never less than a 4-gauge wire. This means that there's essentially no voltage drop between the cap and the battery, so if there's a voltage drop between my cap in the trunk and the headlamps under the hood, it's a deficiency with the headlamp wiring. This is where you're mistaken. 12 ft of *perfect* 4 gauge wire is .003 ohms. The inductance is even more critical (much more critical in fact), but the effect can be described with just the resistance. Anyway, the resistance of 5 ft of 12 ga for the headlights is about .008 ohms. So if you install the cap at the amplifier terminals, the impedance presented to it from the amp is much smaller than .011 ohms and therefore all of the current is essentially delivered to the amplifier. Installing it near the headlights makes the impedance from cap to headlights much smaller than the .011 ohms in the other direction. You can model this with a simple voltage divider circuit putting the cap at different nodes. Maybe I'll put up a website later with the simulations. With the numbers you're using, 0.003 ohms resistance between the battery and the headlamps, and 0.008 ohms between the cap and the battery, I'd consider that "no voltage drop". In this case, your headlamps would have to draw 300 amps of current before they saw a 1-volt drop between the battery and the headlamps, and they ain't ever going to draw that much. Even putting the cap back in the trunk, and using the combined .011 ohms, the headlamps would have to draw 90 amps before the wiring caused a 1-volt drop. This still isn't going to happen. I still say that if putting the capacitor closer to the headlamps versus back in the trunk with the amps makes a big difference in how effectively it reduces flickering, then there's something wrong with your headlamp wiring. Scott Gardner |
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when is capacitors used?
On Sun, 21 Dec 2003 16:17:13 -0500, "Mark Zarella"
wrote: With the numbers you're using, 0.003 ohms resistance between the battery and the headlamps, and 0.008 ohms between the cap and the battery, I'd consider that "no voltage drop". In this case, your headlamps would have to draw 300 amps of current before they saw a 1-volt drop between the battery and the headlamps, and they ain't ever going to draw that much. Even putting the cap back in the trunk, and using the combined .011 ohms, the headlamps would have to draw 90 amps before the wiring caused a 1-volt drop. This still isn't going to happen. I still say that if putting the capacitor closer to the headlamps versus back in the trunk with the amps makes a big difference in how effectively it reduces flickering, then there's something wrong with your headlamp wiring. Using those numbers, I was able to demonstrate this in Multisim's (crappy) simulation software. I've attached a copy of the simulation circuit. It consists of a battery with a finite output Z. An amplifier being treated as an oscillating source (the voltage, mind you, is always below battery voltage so it acts as an oscillating sink). The wires. And the headlights. The values were chosen such that the amp draws roughly 50A peak at 14V, there's about a 1V drop at the battery with 50A draw, and the headlights consume about 120 watts. With no cap, there's an 820mV drop at the amplifier and 720mW drop at the headlights. Putting a 1F cap at the amplifier terminals, the drop at the amplifier is 31mV and at the headlights, 28mV. If the cap is put on the headlight terminals, it's 300mV at the amp and 20mV at the headlights. Hence a reduction. This is hardly a large difference. This is due to a number of factors. First, the wire resistances were the perfect values. In the real world, they'd be much higher. Increasing the resistances uniformly yields an even greater discrepancy between the two setups. To wit, multiplying the wire resistances by 10 gives a ratio od 12:5 instead of 7:5. Secondly, capacitor ESL was ignored. That should reduce both cases equally though, but helps to explain why the dimming on both sides was reduced so dramatically. Most importantly, wire inductance was neglected. This would result in a it for*huge* benefit for the shorter wire, which would be the headlight wire most of the time. Mark, This isn't a binaries newsgroup. I'm not bothered by your posting the .GIF here, but others might complain. So in your circuit simulation, relocating the capacitor from the trunk to right next to the headlamps gave the headlamps an extra 8 millivolts (at the expense of almost a quarter-volt drop at the subs). You've made my point. I agree that your simulation program made some optimistic assumptions, but multiply that 8 millivolts by a factor of ten or twenty, and you STILL won't be able to see a difference. So I go back to my original assertion - if moving the capacitor from the trunk to the headlamp terminals results in noticeably less flickering, then your headlamp wiring is cocked up somehow. Scott Gardner |
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when is capacitors used?
Mark,
This isn't a binaries newsgroup. I'm not bothered by your posting the .GIF here, but others might complain. It's a 5k file. If they have a problem with that, especially given the relevance and importance of the issue (which is probably the most discussed issue in here), then I suggest the get a new newsreader. Or killfile me. So in your circuit simulation, relocating the capacitor from the trunk to right next to the headlamps gave the headlamps an extra 8 millivolts (at the expense of almost a quarter-volt drop at the subs). You've made my point. I agree that your simulation program made some optimistic assumptions, but multiply that 8 millivolts by a factor of ten or twenty, and you STILL won't be able to see a difference. Surely you don't think that the scaling of the simulation is anywhere near realistic. The demonstration showed that a 1F cap lowered the v drop from nearly a volt to under 30mV. Impossible. But the simulation is still illustrative of the fact that location provides an important role. The straight up non-reactive simulation demonstrated a 25% reduction in headlight voltage drop by changing the location. It's hard to argue that 25% isn't significant. That is roughly equivalent to a 25% increase in capacitance! And as I've said throughout the discussion, the non-reactive component doesn't even matter much. I just used it as an illustration of how the inductive component affecteded the outcome, since the mechanism is the same. It's the inductive component that's the kicker, but it's not very easy at all to model that, as the inductance measurement is not as straightforward and there's a temporal component involved. I would guesstimate that the REAL number under realistic conditions is closer to a 50-100% difference in "equivalent" capacitor value. So I go back to my original assertion - if moving the capacitor from the trunk to the headlamp terminals results in noticeably less flickering, then your headlamp wiring is cocked up somehow. Noticeably? I'm not entirely sure it's noticeable. It's probably awfully close to the threshold. I don't know - is there a noticeable difference between, say, 1F and 2F? I think there are a lot of variables at play. But the entire point of my initial assertion was that the capacitor is most effective electrically "close" to the headlights. This is a direct contradicition to the traditional "put it as close to the amplifier as possible" advice. That's my main point. But note also that I said previously that if there are additional reasons for using the capacitor (aesthetic value, for instance), then mount the thing wherever you want. So I'm not trying to convince anyone that it's crucial. I'm just saying that there IS an electrical benefit and that the advice of putting the cap close the amp is wrong. |
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when is capacitors used?
On Sun, 21 Dec 2003 18:22:31 -0500, "Mark Zarella"
wrote: So I go back to my original assertion - if moving the capacitor from the trunk to the headlamp terminals results in noticeably less flickering, then your headlamp wiring is cocked up somehow. Noticeably? I'm not entirely sure it's noticeable. It's probably awfully close to the threshold. I don't know - is there a noticeable difference between, say, 1F and 2F? I think there are a lot of variables at play. But the entire point of my initial assertion was that the capacitor is most effective electrically "close" to the headlights. This is a direct contradicition to the traditional "put it as close to the amplifier as possible" advice. That's my main point. But note also that I said previously that if there are additional reasons for using the capacitor (aesthetic value, for instance), then mount the thing wherever you want. So I'm not trying to convince anyone that it's crucial. I'm just saying that there IS an electrical benefit and that the advice of putting the cap close the amp is wrong. You're right, there IS an electrical benefit to having the capacitor closer to the headlamps, just like a signal-to-noise ratio of 106 dB is better than a S/N ratio of 100 dB. The benefit is there, and it's measureable, but I still don't think it's noticeable. We agree on all of the big points regarding the use of capacitors, so I'm not interested in arguing this relatively insignificant point. I'm just hoping that people start to realize that there's a lot of misinformation out there regarding caps, both pro AND con. For every person that says caps made their system louder, cooler, and made their teeth whiter, there's someone on the other end of the spectrum that says caps are useless "band-aids" that have no place in car audio. Such extreme views don't do anyone any good. Scott Gardner |
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when is capacitors used?
X-No-Archive: Yes
A capacitor is basically a reservior with a very small internal resistance. It is very effective at supplying a very high instantaneous current. It's best placed as close as possible to load requiring high instantaneous current. When there's a demand for more power, electricity comes from a source with smallest impedance. In this case, a low internal resistance capacitor placed within a foot of amplifier rather than from rather high internal resitance battery connected a few feet away. By letting the capacitor supply peak demand, you can reduce the sagging on upstream. Johan Wagener wrote: I heard that the car battery cannot supply current at a fast enough rate (because of chemical reaction neccesary) for subwoofers and that a cap is needed. At what power ratings should one start to worry about this? |
#33
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when is capacitors used?
In article ,
"Johan Wagener" wrote: I heard that the car battery cannot supply current at a fast enough rate (because of chemical reaction neccesary) for subwoofers and that a cap is needed. At what power ratings should one start to worry about this? When the current is high enough to worry, you're in need of more storage than the usual 1 to 3 F cap. Car audio stiffening caps are mostly a gimmick. |
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when is capacitors used?
"Johan Wagener" wrote in message
... I heard that the car battery cannot supply current at a fast enough rate (because of chemical reaction neccesary) for subwoofers and that a cap is needed. At what power ratings should one start to worry about this? some people don't realize that if you have a fully regulated amp, you get little to no benefits. if it's un-or-semi regulated you may/can see some benefits |
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when is capacitors used?
"Kevin McMurtrie" wrote in message
... In article , "Johan Wagener" wrote: I heard that the car battery cannot supply current at a fast enough rate (because of chemical reaction neccesary) for subwoofers and that a cap is needed. At what power ratings should one start to worry about this? When the current is high enough to worry, you're in need of more storage than the usual 1 to 3 F cap. Car audio stiffening caps are mostly a gimmick. explain who there a gimmick, if you need a big boost of volts for a bass note you'll need the cap then the batt. will never get the power down the line quickly enough. |
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when is capacitors used?
explain who there a gimmick, if you need a big boost of volts for a bass
note you'll need the cap then the batt. will never get the power down the line quickly enough. What do you mean? It moves at the speed of light. |
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when is capacitors used?
At what power ratings should one start to worry about this?
some people don't realize that if you have a fully regulated amp, you get little to no benefits. if it's un-or-semi regulated you may/can see some benefits How do you figure? Headlight dimming would be more pronounced if anything for a fully regulated amp. |
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when is capacitors used?
Just to add alittle to the Headlight dimming and the cap issue. Take the
cars charging system. Simulations lack Time Lag for the Regulator to pick up on a Voltage fluctuation. Not to mention that the Cars electrical system is run buy the alt when running. WHen demads are high enough the Alt cannot keep up and we have Voltage sag, which inturn drops the enitire voltage of the charging system. Seeing that almost all electrical components are in parallel with the Alt and battery. That fluctuation will be felt throughout the electrical system. So those that say if a 50A draw causes a 1V flucuation at the amp that sag will be produced throughout the entire system. Not to mention that most auto manufactures do not use the best techniques for wiring Headlights. Their are reasons why wpoplw rewire Headlights with Bigger Ga. Wire, Relay's and use the Head light switch wiring for Relay activation. -- 1991 Tornado Red Corrado, CCA Member # 6645 Stereo is a continuous W.I.P. There are two parts to wisdom: 1) Having a lot to say, and 2) Not saying it. |
#39
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when is capacitors used?
Just to add alittle to the Headlight dimming and the cap issue. Take the
cars charging system. Simulations lack Time Lag for the Regulator to pick up on a Voltage fluctuation. Not if you make the current draw frequency low enough. You could even attempt to simulate the PWM action by putting a high frequency in the low freq envelope. But it's unnecessary for our purposes. Not to mention that the Cars electrical system is run buy the alt when running. That's easily simulated. Just raise the voltage and modify the output Z. Or if you want to get really fancy, put a second source in parallel. WHen demads are high enough the Alt cannot keep up and we have Voltage sag, which inturn drops the enitire voltage of the charging system. Seeing that almost all electrical components are in parallel with the Alt and battery. That fluctuation will be felt throughout the electrical system. So those that say if a 50A draw causes a 1V flucuation at the amp that sag will be produced throughout the entire system. Correct. The fluctuation is the result of the output impedance of the source. Not to mention that most auto manufactures do not use the best techniques for wiring Headlights. Their are reasons why wpoplw rewire Headlights with Bigger Ga. Wire, Relay's and use the Head light switch wiring for Relay activation. Right. Many manufacturers run the headlight power all the way to the dash, through the switches, and back again. People often modify the circuit so this wire drives a relay. This is done to improve the total output of the headlights. But it actually does not improve the flickering! |
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when is capacitors used?
"Mark Zarella" wrote in message
... explain who there a gimmick, if you need a big boost of volts for a bass note you'll need the cap then the batt. will never get the power down the line quickly enough. What do you mean? It moves at the speed of light. electricy does not always move at the speed of light, it depends on the medium |
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