Reply
 
Thread Tools Display Modes
  #1   Report Post  
Johan Wagener
 
Posts: n/a
Default 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   Report Post  
Anb
 
Posts: n/a
Default 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   Report Post  
Mark Zarella
 
Posts: n/a
Default 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   Report Post  
Scott Gardner
 
Posts: n/a
Default 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   Report Post  
Mark Zarella
 
Posts: n/a
Default 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   Report Post  
Scott Gardner
 
Posts: n/a
Default 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   Report Post  
Mark Zarella
 
Posts: n/a
Default 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   Report Post  
Aaron
 
Posts: n/a
Default 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   Report Post  
Mark Zarella
 
Posts: n/a
Default 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   Report Post  
Aaron
 
Posts: n/a
Default 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   Report Post  
Soundfreak03
 
Posts: n/a
Default 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   Report Post  
Mark Zarella
 
Posts: n/a
Default 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   Report Post  
Aaron
 
Posts: n/a
Default 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   Report Post  
Aaron
 
Posts: n/a
Default 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   Report Post  
Soundfreak03
 
Posts: n/a
Default 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   Report Post  
Mark Zarella
 
Posts: n/a
Default 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   Report Post  
Aaron
 
Posts: n/a
Default 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   Report Post  
Aaron
 
Posts: n/a
Default 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   Report Post  
Mark Zarella
 
Posts: n/a
Default 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   Report Post  
Aaron
 
Posts: n/a
Default 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   Report Post  
Donald Sherwood
 
Posts: n/a
Default 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   Report Post  
Soundfreak03
 
Posts: n/a
Default 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   Report Post  
Scott Gardner
 
Posts: n/a
Default 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   Report Post  
Stevo
 
Posts: n/a
Default 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
  #25   Report Post  
Scott Gardner
 
Posts: n/a
Default when is capacitors used?

On 21 Dec 2003 00:47:27 -0800, (Stevo)
wrote:

"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


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. 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. Other people's installs may have different results.
Also, Mark makes the point that just because you're seeing
flickering of your headlamps and/or dash lighting, the rest of your
car , including your stereo, may be perfectly happy. Lights will
noticeably flicker with as little as a 1-volt drop, but things like
ignition systems, computers, and most stereo components are regulated
to work just fine with anything from 11V or lower up to 16V. Even if
you have an unregulated power supply in your amplifier, the
short-duration voltage drop probably isn't going to be noticeable to
your ears, even if it causes your lights to flicker.

Scott Gardner


  #26   Report Post  
Mark Zarella
 
Posts: n/a
Default 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   Report Post  
Mark Zarella
 
Posts: n/a
Default 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.


  #28   Report Post  
Scott Gardner
 
Posts: n/a
Default 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


  #29   Report Post  
Scott Gardner
 
Posts: n/a
Default 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

  #30   Report Post  
Mark Zarella
 
Posts: n/a
Default 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.




  #31   Report Post  
Scott Gardner
 
Posts: n/a
Default 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

  #32   Report Post  
AC/DCdude17
 
Posts: n/a
Default 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   Report Post  
Kevin McMurtrie
 
Posts: n/a
Default 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.
  #34   Report Post  
Tha Ghee
 
Posts: n/a
Default 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


  #35   Report Post  
Tha Ghee
 
Posts: n/a
Default 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.




  #36   Report Post  
Mark Zarella
 
Posts: n/a
Default 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.


  #37   Report Post  
Mark Zarella
 
Posts: n/a
Default 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.


  #38   Report Post  
Donald Sherwood
 
Posts: n/a
Default 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   Report Post  
Mark Zarella
 
Posts: n/a
Default 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!


  #40   Report Post  
Tha Ghee
 
Posts: n/a
Default 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


Reply
Thread Tools
Display Modes

Posting Rules

Smilies are On
[IMG] code is On
HTML code is Off


Similar Threads
Thread Thread Starter Forum Replies Last Post
Capacitors Bryan Car Audio 0 December 2nd 03 04:23 AM
FA: Sprague NOS "Black Beauty" Capacitors and More! Rick Ferranti General 0 December 1st 03 06:51 PM
fs: 1 Farad Capacitors Eric Renaud Car Audio 0 October 26th 03 11:13 PM
FS: (3) 1 Farad Capacitors Eric Renaud Car Audio 1 October 1st 03 11:59 PM
CAPACITORS good inexexpensive? Soundfreak03 Car Audio 7 July 23rd 03 09:50 PM


All times are GMT +1. The time now is 06:44 PM.

Powered by: vBulletin
Copyright ©2000 - 2024, Jelsoft Enterprises Ltd.
Copyright ©2004-2024 AudioBanter.com.
The comments are property of their posters.
 

About Us

"It's about Audio and hi-fi"