Capacitors

[Nathan]

When should you consider getting a capacitor for your car audio
system. Would 800watts be helped out by a capacitor or would it just
be a waste of money.

[trex160s]

people always get caps b/c there lights are dimming. i dont know why
they waist there money on them a 2nd battery will work better. upgrade
the car battery to the biggest cca that you can fit then upgrade all
wires to the alt and then upgrade alt .caps are a temp fix do it right
the frist time and save the money from the cap and get the alt
--
trex160s
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[Web Guru]

Here is my experience: I had 500W Amp. + JLW6, when I cranked up my music
without the cap., and whenever it came across strong bass, the amp. shut
down by itself (underpowered) and then turned back on after 5 sec. so I
installed a 1 Farad cap. and solved the problem!

Side notes: I didn't see a lot light dimming, only slightly.. so light
dimming wasn't a good indicator in my case.


"Nathan" > wrote in message
om...
> When should you consider getting a capacitor for your car audio
> system. Would 800watts be helped out by a capacitor or would it just
> be a waste of money.

[capone]

i had a 1 farad cap on my rf 800a2 and it didnt do didly squat


--
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[-E-F-F-E-N-D-I-]

I eould highly reccomend againtst a cap. yeah some of them look cool and
unless you are planning on a show setup there aint no point to having one.
In mine and most others opinion a second battery with an isolator and a
higher amp capable alternator (or two or more even) will give you much
better results. Even if you only change your stock battery to something like
an Optima RedTop you might notice some performance gain.

EFFENDI

"Nathan" > wrote in message
om...
> When should you consider getting a capacitor for your car audio
> system. Would 800watts be helped out by a capacitor or would it just
> be a waste of money.

[Taffer Garrett]

FYI, Adding a "stiffening" capacitor to a fully regulated amplifier won't
even help at all. You can tell if your amplifier has a fully regulated
supply by checking to see if it has a secondary storage device in the amps
PS. Usually, it will be another ferrite core wound with wire just like the
PS transformer. I wouldn't recommend opening your amp up just to check, but
I would tell you to contact your amp manufacture's tech support and ask
them.

Adding a second, isolated battery/alternator UG is always good. Keeps you
from stranding you somewhere with a dead battery ( if done proper ) as well
as adding capacity. Just be sure and use a sealed battery if you plan on
placing it in the trunk. It is against the law in many states to put a
vented battery in a "sealed" or passenger area. Vented batteries give off
poisonous/corrosive/explosive vapors when charged.

Taffer Garrett

"Nathan" > wrote in message
om...
> When should you consider getting a capacitor for your car audio
> system. Would 800watts be helped out by a capacitor or would it just
> be a waste of money.

[sanitarium]

I have no first hand experience with Caps in my system. I never felt the
need for one. If my amps were overloading the electrical system in any way
I wouldn't fix it with a cap. My choice would be a high output alternator.

This is my understanding....
Its a product that many times does nothing to improve SQ or SPL. IMHO its
used as a band aid, quick fix to try and cover up an overloaded alternator.
Your SPL scores will not improve, if anything your SPL will decrease, as the
cap is placing an additional load on the alternator. If your headlights are
dimming, adding a cap will provide extra current for transient peaks, but at
the same time youre adding a load to the alternator and taking precious
power away from your amps.

Again, I dont have first hand experience with caps in my system... unless
someone can convince me they are worth the $$$ :~) If I did need an
electrical system upgrade an alternator would be my choice.... fix the root
cause.

Garrett

"Nathan" > wrote in message
om...
> When should you consider getting a capacitor for your car audio
> system. Would 800watts be helped out by a capacitor or would it just
> be a waste of money.

[Chris]

Just put .05f caps on your headlights if it bothers you so much
"sanitarium" > wrote in message
news:1065206183.423449@sj-nntpcache-5...
> I have no first hand experience with Caps in my system. I never felt the
> need for one. If my amps were overloading the electrical system in any
way
> I wouldn't fix it with a cap. My choice would be a high output
alternator.
>
> This is my understanding....
> Its a product that many times does nothing to improve SQ or SPL. IMHO its
> used as a band aid, quick fix to try and cover up an overloaded
alternator.
> Your SPL scores will not improve, if anything your SPL will decrease, as
the
> cap is placing an additional load on the alternator. If your headlights
are
> dimming, adding a cap will provide extra current for transient peaks, but
at
> the same time youre adding a load to the alternator and taking precious
> power away from your amps.
>
> Again, I dont have first hand experience with caps in my system... unless
> someone can convince me they are worth the $$$ :~) If I did need an
> electrical system upgrade an alternator would be my choice.... fix the
root
> cause.
>
> Garrett
>
> "Nathan" > wrote in message
> om...
> > When should you consider getting a capacitor for your car audio
> > system. Would 800watts be helped out by a capacitor or would it just
> > be a waste of money.
>
>

[Tha Ghee]

"trex160s" > wrote in message
s.com...
people always get caps b/c there lights are dimming. i dont know why they
waist there money on them a 2nd battery will work better. upgrade the car
battery to the biggest cca that you can fit then upgrade all wires to the
alt and then upgrade alt .caps are a temp fix do it right the frist time
and save the money from the cap and get the alt

you do realize that if you don't upgrade the alt first you can make the
situation worse. the proper setup should be, wire, alt, batt, and cap, in
that order.

[capone]

caps are junk!


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[Paul Vina]

s.com...
> people always get caps b/c there lights are dimming. i dont know why they
> waist there money on them a 2nd battery will work better. upgrade the car
> battery to the biggest cca that you can fit


Not even close. All a bigger battery does is provide more engine off
listening time. When the car is running the battery is nothing more than a
load, just like a light or your defroster.


then upgrade all wires to the
> alt and then upgrade alt .caps are a temp fix do it right the frist time
> and save the money from the cap and get the alt

I agree about upgrading the alternator first, but a cap does a different
job.



> you do realize that if you don't upgrade the alt first you can make the
> situation worse.

Care to explain how? Cuz that's total BS.



the proper setup should be, wire, alt, batt, and cap, in
> that order.

Really? I've never change a battery in any of my cars, including my
competition cars.


Paul Vina

[Paul Vina]

Only if you're trying to get it to do something it wasn't meant to do. Caps
aren't meant to keep headlight from dimming, they're to provide voltage
quickly when the alternator can't keep up, but only for very quick bursts.


Paul Vina



"capone" > wrote in message
...
>
> caps are junk!
>
>
> --
> capone
> ------------------------------------------------------------------------
> Posted via RealCarAudio.com - The checkmate of the caraudio community.
> http://www.RealCarAudio.com
> capone's Profile:
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> View this thread:
http://www.realcaraudio.com/forums/showthread.php?threadid=9898
>

[Scott Gardner]

I'll second the opinion that additional batteries and/or
larger batteries are unnecessary. Batteries are for starting the car
or running the system with the engine off - that's all.

Furthermore, alternators only need to be able to keep up with
the *average* current demand, not the *peak* demand. As long as you
can drive around all day listening to music at your normal volume and
not drain your battery, your alternator is sufficient. Now, for those
large transient peaks that your alternator *can't* handle, that's
where capacitors come in. Caps have an extremely low internal
resistance, so they can provide huge bursts of current for short
periods of time with almost no voltage drop. As long as your
alternator can handle your car's average current requirements, it's
not a "band-aid" or bad engineering to use a capacitor to handle the
transients.

Think of a typical toilet. When flushed, they have to be able
to get rid of about a gallon of water in 10 or 15 seconds (about 4-6
gallons per minute). Now look at the water supply line coming in from
the wall. Odds are, it's so small that it could never flow the
required 4-6 gallons per minute to handle a flush. How do they get
around this problem? The toilet tank that sits on top of the bowl
holds a gallon or so of water in reserve. This tank is refilled from
the small-diameter supply line in-between flushes. If you didn't use
a tank, the only other option would be to use a much bigger supply
line that could handle the peak flow rate required for a flush.

In a car, the supply line would be the alternator, the toilet
tank would be the capacitor, and flushing the toilet would be an
example of a peak transient. As long as your tank is big enough to
handle the transient peaks, you can get away with a smaller supply
line.


Scott Gardner



On Fri, 17 Oct 2003 22:06:22 -0400, "Tha Ghee" >
wrote:

>
>"trex160s" > wrote in message
s.com...
>people always get caps b/c there lights are dimming. i dont know why they
>waist there money on them a 2nd battery will work better. upgrade the car
>battery to the biggest cca that you can fit then upgrade all wires to the
>alt and then upgrade alt .caps are a temp fix do it right the frist time
>and save the money from the cap and get the alt
>
>you do realize that if you don't upgrade the alt first you can make the
>situation worse. the proper setup should be, wire, alt, batt, and cap, in
>that order.
>
>

[Mark Zarella]

> I'll second the opinion that additional batteries and/or
> larger batteries are unnecessary. Batteries are for starting the car
> or running the system with the engine off - that's all.

Batteries do in fact supply current to the audio system. Try running a
system with the car on and the battery disconnected. Oftentimes the
amplifiers will shut off due to voltage below threshold. In addition, a
poor battery will draw excess current from the alternator when charging.
This also has a detrimental effect.

> Furthermore, alternators only need to be able to keep up with
> the *average* current demand, not the *peak* demand. As long as you
> can drive around all day listening to music at your normal volume and
> not drain your battery, your alternator is sufficient. Now, for those
> large transient peaks that your alternator *can't* handle, that's
> where capacitors come in. Caps have an extremely low internal
> resistance, so they can provide huge bursts of current for short
> periods of time with almost no voltage drop.

The voltage drop is proportional to the time. That means that there's
ALWAYS a voltage drop as the capacitor discharges, and it can become
quite substantial for "typical" (whatever that is) transients. This can
all be verified with mathematics also.

> As long as your
> alternator can handle your car's average current requirements, it's
> not a "band-aid" or bad engineering to use a capacitor to handle the
> transients.

The engineers already put them inside the amp. Are you suggesting their
engineering is inadequate?

[Captain Howdy]

>
>Batteries do in fact supply current to the audio system. Try running a
>system with the car on and the battery disconnected.

That's a sure way of damaging your alternator.

Oftentimes the
>amplifiers will shut off due to voltage below threshold.

Yes they will, alternators do not respond fast enough to power peaks, causing
voltage drops triggering under-voltage protecting in the amplifier, shutting
it off . That's where a capacitor comes in to play.

In addition, a
>poor battery will draw excess current from the alternator when charging.
> This also has a detrimental effect.

What is a poor battery, a faulty one ?
>.
>
>The voltage drop is proportional to the time. That means that there's
>ALWAYS a voltage drop as the capacitor discharges, and it can become
>quite substantial for "typical" (whatever that is) transients. This can
>all be verified with mathematics also.

True, most this voltage drop occurs between the battery and capacitor and not
as much so between the capacitor and amplifier.
>

>>The engineers already put them inside the amp. Are you suggesting their
>engineering is inadequate?

Yes, Mid-grade amplifiers such as some Kenwood, Alpine amplifiers, use paper
electrolytic capacitors that are way to small for their application. Not that
long ago, I have bench tested a Profile 200 watt rms mono block amplifier
after replacing a few burnt out output mosfets. At 14 volts with a current
draw of about 18amps at peak the power led stated dimming. At that point i
have ripped the amplifier apart again and upgraded the power hexfets to lager
ones, I also doubled the size of the power capacitors and changed them from
paper film to aluminum film capacitors, and that totally eliminated the power
led dimming problem that this amplifier had at high volumes.

[Mark Zarella]

>>Batteries do in fact supply current to the audio system. Try running a
>>system with the car on and the battery disconnected.
>
>
> That's a sure way of damaging your alternator.

No it isn't. It can be damaging to your sensitive electronics, but you
won't burn out your alternator.

> Oftentimes the
>
>>amplifiers will shut off due to voltage below threshold.
>
>
> Yes they will, alternators do not respond fast enough to power peaks, causing
> voltage drops triggering under-voltage protecting in the amplifier, shutting
> it off . That's where a capacitor comes in to play.

Or a battery. It's not a matter of alternators not responding "fast
enough". They respond as fast as a battery, yet the battery hooked up
still prevents the undervoltage state from occurring. It's a matter of
the alternator simply not being able to supply enough current during the
transients. As a result, the voltage drop is substantial. If the
battery is hooked up, it can provide the excess current. If a capacitor
is hooked up instead of a battery, it can provide the current assuming
the transient is short enough. This is usually not the case.


> In addition, a
>
>>poor battery will draw excess current from the alternator when charging.
>> This also has a detrimental effect.
>
>
> What is a poor battery, a faulty one ?

Yeah. One that should be replaced.

>>The voltage drop is proportional to the time. That means that there's
>>ALWAYS a voltage drop as the capacitor discharges, and it can become
>>quite substantial for "typical" (whatever that is) transients. This can
>>all be verified with mathematics also.
>
>
> True, most this voltage drop occurs between the battery and capacitor and not
> as much so between the capacitor and amplifier.

Not sure what you mean here. There should be a very small voltage drop
(less than a volt) between battery and amplifier/capacitor. But it
doesn't take much at all for the capacitor to half-discharge in a very
small time (shorter than a "typical" transient), in the process having a
steep v drop.

>>>The engineers already put them inside the amp. Are you suggesting their
>>
>>engineering is inadequate?
>
>
> Yes, Mid-grade amplifiers such as some Kenwood, Alpine amplifiers, use paper
> electrolytic capacitors that are way to small for their application. Not that
> long ago, I have bench tested a Profile 200 watt rms mono block amplifier
> after replacing a few burnt out output mosfets. At 14 volts with a current
> draw of about 18amps at peak the power led stated dimming. At that point i
> have ripped the amplifier apart again and upgraded the power hexfets to lager
> ones, I also doubled the size of the power capacitors and changed them from
> paper film to aluminum film capacitors, and that totally eliminated the power
> led dimming problem that this amplifier had at high volumes.

You don't know that this was an effective upgrade. An LED's performance
is hardly indicative. First, the LED is not run off the rails; second,
you don't know if LED flicker translates into an audible effect. I
sincerely doubt it did.

[Captain Howdy]

In article >, Mark Zarella > wrote:
>>>Batteries do in fact supply current to the audio system. Try running a
>>>system with the car on and the battery disconnected.
>>
>>
>> That's a sure way of damaging your alternator.
>
>No it isn't. It can be damaging to your sensitive electronics, but you
>won't burn out your alternator.

Where did you get this infomation? Never operate an alternator on an
open circuit. With no battery or electrical load in the circuit,
alternators are capable of building high voltage (50 to over 110 volts)
which may damage diodes and endanger anyone who touches the
alternator output terminal.




>>
>>
>> Yes, Mid-grade amplifiers such as some Kenwood, Alpine amplifiers, use paper
>> electrolytic capacitors that are way to small for their application. Not that
>
>> long ago, I have bench tested a Profile 200 watt rms mono block amplifier
>> after replacing a few burnt out output mosfets. At 14 volts with a current
>> draw of about 18amps at peak the power led stated dimming. At that point i
>> have ripped the amplifier apart again and upgraded the power hexfets to lager
>
>> ones, I also doubled the size of the power capacitors and changed them from
>> paper film to aluminum film capacitors, and that totally eliminated the power
>
>> led dimming problem that this amplifier had at high volumes.
>
>You don't know that this was an effective upgrade. An LED's performance
>is hardly indicative. First, the LED is not run off the rails; second,
>you don't know if LED flicker translates into an audible effect. I
>sincerely doubt it did.

No the led is not run of the rails. But it is run off the internal power
supply, which is feed in part from the internal capacitors. Your average (5mm)
LED runs at 3.5- 5 volts DC with a current drain of 25mA. When the LED starts
dimming, this is a sure sign of internal under-voltage. This creates DC
ripples, need I say more?

[Mark Zarella]

Captain Howdy wrote:
> In article >, Mark Zarella > wrote:
>
>>>>Batteries do in fact supply current to the audio system. Try running a
>>>>system with the car on and the battery disconnected.
>>>
>>>
>>>That's a sure way of damaging your alternator.
>>
>>No it isn't. It can be damaging to your sensitive electronics, but you
>>won't burn out your alternator.
>
>
> Where did you get this infomation? Never operate an alternator on an
> open circuit. With no battery or electrical load in the circuit,
> alternators are capable of building high voltage (50 to over 110 volts)
> which may damage diodes and endanger anyone who touches the
> alternator output terminal.

Usually the regulator will prevent this from occurring. It's certainly
not a "sure way" to burn out an alternator becuse it's happened to me
several times and never did I burn out an alternator! (a computer, but
not an alternator :) )


>>>Yes, Mid-grade amplifiers such as some Kenwood, Alpine amplifiers, use paper
>>>electrolytic capacitors that are way to small for their application. Not that
>>
>>>long ago, I have bench tested a Profile 200 watt rms mono block amplifier
>>>after replacing a few burnt out output mosfets. At 14 volts with a current
>>>draw of about 18amps at peak the power led stated dimming. At that point i
>>>have ripped the amplifier apart again and upgraded the power hexfets to lager
>>
>>>ones, I also doubled the size of the power capacitors and changed them from
>>>paper film to aluminum film capacitors, and that totally eliminated the power
>>
>>>led dimming problem that this amplifier had at high volumes.
>>
>>You don't know that this was an effective upgrade. An LED's performance
>>is hardly indicative. First, the LED is not run off the rails; second,
>>you don't know if LED flicker translates into an audible effect. I
>>sincerely doubt it did.
>
>
> No the led is not run of the rails. But it is run off the internal power
> supply, which is feed in part from the internal capacitors. Your average (5mm)
> LED runs at 3.5- 5 volts DC with a current drain of 25mA. When the LED starts
> dimming, this is a sure sign of internal under-voltage. This creates DC
> ripples, need I say more?

a) Undervoltage condition is generally indetectable by the human ear.
b) This does NOT in and of itself create ripples in the rails.
Especially in a semi-regulated supply, and global NFB design. Any
ripple that did make itself through both barriers generally causes
inaudible effects anyway.

In other words, voltage fluctuations don't matter, unless headlight
dimming really bothers you. In that case, there are other more
effective ways of dealing with the issue.

[Scott Gardner]

On Sun, 30 Nov 2003 03:00:49 GMT, Mark Zarella
> wrote:

>> I'll second the opinion that additional batteries and/or
>> larger batteries are unnecessary. Batteries are for starting the car
>> or running the system with the engine off - that's all.
>
>Batteries do in fact supply current to the audio system. Try running a
>system with the car on and the battery disconnected. Oftentimes the
>amplifiers will shut off due to voltage below threshold. In addition, a
>poor battery will draw excess current from the alternator when charging.
> This also has a detrimental effect.
>
I agree that the battery will provide current when the
alternator cannot keep up with the load. Unfortuneately, the battery
is a poor candidate for this job, since it has a relatively high
internal resistance. This resistance, combined with a high current
drain, will cause a significant voltage drop. This is why it's
acceptable for even a "good" battery to drop from 12V all the way down
to 9.6V while cranking over the engine.
Capacitors have a MUCH small internal resistance, so they can
provide a larger surge of current without a corresponding large
voltage drop.

>> Furthermore, alternators only need to be able to keep up with
>> the *average* current demand, not the *peak* demand. As long as you
>> can drive around all day listening to music at your normal volume and
>> not drain your battery, your alternator is sufficient. Now, for those
>> large transient peaks that your alternator *can't* handle, that's
>> where capacitors come in. Caps have an extremely low internal
>> resistance, so they can provide huge bursts of current for short
>> periods of time with almost no voltage drop.
>

>The voltage drop is proportional to the time. That means that there's
>ALWAYS a voltage drop as the capacitor discharges, and it can become
>quite substantial for "typical" (whatever that is) transients. This can
>all be verified with mathematics also.

Again, you're absolutely right. There is a voltage drop across the
capacitor's terminals as a load is applied, but we can vary how
quickly the voltage drops by varying the capacitance. Depending on
our needs for a particular installation, we can make the discharge
time constant equal to whatever we want by using smaller or larger
capacitors.
>
>> As long as your
>> alternator can handle your car's average current requirements, it's
>> not a "band-aid" or bad engineering to use a capacitor to handle the
>> transients.
>
>The engineers already put them inside the amp. Are you suggesting their
>engineering is inadequate?
>
I think the engineers do the best they can within the
constraints of packaging size, cost, and the fact that they can't
predict how exactly the amp will be used. They don't know how much
capacity your car's alternator has, or what other loads are sharing
that capacity.
My guidance is that unless you know for certain that
your stock alternator isn't up to the task (like trying to put 3000
watts of amplification in a stock Civic), give it a try without
upgrading the alternator or adding a capacitor. If you can drive
around all day playing music at your normal levels without discharging
the battery, then your alternator is obviously capable of handling the
*average* load you're putting on it. At this point, either
everything's good, or you're getting some dimming of lights during
large transients. Now, I would try a capacitor. Start off with the 1
Farad/kW estimate and go from there. If that still doesn't solve the
problem, you have to find out which is cheaper - more capacitance, or
a higher-capacity alternator. Some applications are cheap - you can
get 150A alternators for Hondas for less than $250. For older or more
offbeat cars, the choices are slimmer.
I'm not saying that every installation needs a capacitor, and
I'll admit that beyond a certain point, it becomes more cost-effective
to put in a higher-capacity alternator. I'm just responding to the
people that make blanket statements like "capacitors suck", or blindly
follow rules-of-thumb like "one Farad per 1,000 watts amplifier
power".

Scott Gardner

[Captain Howdy]

In article >, Mark Zarella > wrote:

>>
>> Where did you get this infomation? Never operate an alternator on an
>> open circuit. With no battery or electrical load in the circuit,
>> alternators are capable of building high voltage (50 to over 110 volts)
>> which may damage diodes and endanger anyone who touches the
>> alternator output terminal.
>
>Usually the regulator will prevent this from occurring. It's certainly
>not a "sure way" to burn out an alternator becuse it's happened to me
>several times and never did I burn out an alternator! (a computer, but
>not an alternator :) )
>

Okay Mark, It seems that at this point, you agree on the fact that running
your alternator without a battery will cause damage. For someone such as
yourself that has been here for a long while, you are fully aware that this
news group is mostly for newbies to have a place to go to for advice. Why
would you tell someone to run their alternator without a battery when you know
that you can do serious damage by doing so?

For anyone in doubt, checkout
http://www3.telus.net/DonsMiniSite/MiniTek_Alternator.html
http://www.tpub.com/content/construction/14273/css/14273_51.htm
http://www.allpar.com/eek/alternators.html






>
>
>a) Undervoltage condition is generally indetectable by the human ear.

Undervoltage tends to overheat transistors, causing your amplifier to go in
to thermal protection and shutting the amlifier off making this detectable by
the human ear. It also creates distortion at lower power levels, which may
damage your speakers.

http://www.polkaudio.com/car/faqad/advice.php?article=hownottowax





>
>In other words, voltage fluctuations don't matter,

Are you totally sure?

unless headlight
>dimming really bothers you. In that case, there are other more
>effective ways of dealing with the issue.

Care to share?
>

[Mark Zarella]

>Batteries do in fact supply current to the audio system. Try running a
>>system with the car on and the battery disconnected. Oftentimes the
>>amplifiers will shut off due to voltage below threshold. In addition, a
>>poor battery will draw excess current from the alternator when charging.
>> This also has a detrimental effect.
>>
>
> I agree that the battery will provide current when the
> alternator cannot keep up with the load. Unfortuneately, the battery
> is a poor candidate for this job, since it has a relatively high
> internal resistance. This resistance, combined with a high current
> drain, will cause a significant voltage drop. This is why it's
> acceptable for even a "good" battery to drop from 12V all the way down
> to 9.6V while cranking over the engine.
> Capacitors have a MUCH small internal resistance, so they can
> provide a larger surge of current without a corresponding large
> voltage drop.

Batteries are an integral part of the audio system. Certainly moreso
than a capacitor. The benefits of added capacitance do not
significantly contribute to the alternator's net output. The same
cannot be said of batteries. Although the output impedance of a battery
is greater than that of a capacitor, the amount of energy it stores and
therefore can deliver is much greater. Capacitors are useless for
trying to keep up with musical transients, which tend to last longer
than the usable discharge time of a 1 to few farad capacitor.

>>The voltage drop is proportional to the time. That means that there's
>>ALWAYS a voltage drop as the capacitor discharges, and it can become
>>quite substantial for "typical" (whatever that is) transients. This can
>>all be verified with mathematics also.
>
>
> Again, you're absolutely right. There is a voltage drop across the
> capacitor's terminals as a load is applied, but we can vary how
> quickly the voltage drops by varying the capacitance. Depending on
> our needs for a particular installation, we can make the discharge
> time constant equal to whatever we want by using smaller or larger
> capacitors.

Yeah, and for practical applications, this requires a pretty huge amount
of capacitance. And for what benefit?

>>> As long as your
>>>alternator can handle your car's average current requirements, it's
>>>not a "band-aid" or bad engineering to use a capacitor to handle the
>>>transients.
>>
>>The engineers already put them inside the amp. Are you suggesting their
>>engineering is inadequate?
>>
>
> I think the engineers do the best they can within the
> constraints of packaging size, cost, and the fact that they can't
> predict how exactly the amp will be used. They don't know how much
> capacity your car's alternator has, or what other loads are sharing
> that capacity.
> My guidance is that unless you know for certain that
> your stock alternator isn't up to the task (like trying to put 3000
> watts of amplification in a stock Civic), give it a try without
> upgrading the alternator or adding a capacitor. If you can drive
> around all day playing music at your normal levels without discharging
> the battery, then your alternator is obviously capable of handling the
> *average* load you're putting on it.

If your battery is discharging, there's no amount of capacitance that
will help.

> At this point, either
> everything's good, or you're getting some dimming of lights during
> large transients. Now, I would try a capacitor. Start off with the 1
> Farad/kW estimate and go from there. If that still doesn't solve the
> problem, you have to find out which is cheaper - more capacitance, or
> a higher-capacity alternator. Some applications are cheap - you can
> get 150A alternators for Hondas for less than $250. For older or more
> offbeat cars, the choices are slimmer.
> I'm not saying that every installation needs a capacitor, and
> I'll admit that beyond a certain point, it becomes more cost-effective
> to put in a higher-capacity alternator. I'm just responding to the
> people that make blanket statements like "capacitors suck", or blindly
> follow rules-of-thumb like "one Farad per 1,000 watts amplifier
> power".

I know of no practical applications where a capacitor is a more viable
option, aside from trying to prevent dimming by putting them as close to
the headlights as possible. Yet the reasons most often attributed to
adding capacitance tend to be to improve sound in some fashion by
mounting them as close to the amplifiers as possible - total bull.

[Mark Zarella]

Captain Howdy wrote:
> In article >, Mark Zarella > wrote:
>
>
>>>Where did you get this infomation? Never operate an alternator on an
>>>open circuit. With no battery or electrical load in the circuit,
>>>alternators are capable of building high voltage (50 to over 110 volts)
>>>which may damage diodes and endanger anyone who touches the
>>>alternator output terminal.
>>
>>Usually the regulator will prevent this from occurring. It's certainly
>>not a "sure way" to burn out an alternator becuse it's happened to me
>>several times and never did I burn out an alternator! (a computer, but
>>not an alternator :) )
>>
>
>
> Okay Mark, It seems that at this point, you agree on the fact that running
> your alternator without a battery will cause damage.

When did I say otherwise?

> For someone such as
> yourself that has been here for a long while, you are fully aware that this
> news group is mostly for newbies to have a place to go to for advice. Why
> would you tell someone to run their alternator without a battery when you know
> that you can do serious damage by doing so?

I didn't literally mean to go out and try it!

>>a) Undervoltage condition is generally indetectable by the human ear.
>
>
> Undervoltage tends to overheat transistors, causing your amplifier to go in
> to thermal protection and shutting the amlifier off making this detectable by
> the human ear.

Wrong. Which transistors are they overheating?

> It also creates distortion at lower power levels,

How??

> which may
> damage your speakers.

How?? We've addressed the "distortion blows speakers" myth in here ad
nauseum, and have demonstrated it to be total trash. Quite simply,
lower voltage means less power which means you're less likely to blow
your speaker. There's nothing more to it.

> http://www.polkaudio.com/car/faqad/advice.php?article=hownottowax

www.geocities.com/audiotechpages/clipping/clippingframes.html

>>In other words, voltage fluctuations don't matter,
>
>
> Are you totally sure?

Totally.


>
> unless headlight
>
>>dimming really bothers you. In that case, there are other more
>>effective ways of dealing with the issue.
>
>
> Care to share?

Anywhere from installing small capacitors near the headlights (I've
installed 100,000 uF caps) to actual diode isolation in serious
situations. If it gets too serious, you can start damaging things like
computers and the like. In that case, no amount of capacitance will
save you.

[Captain Howdy]

>
>I know of no practical applications where a capacitor is a more viable
>option, aside from trying to prevent dimming by putting them as close to
>the headlights as possible. Yet the reasons most often attributed to
>adding capacitance tend to be to improve sound in some fashion by
>mounting them as close to the amplifiers as possible - total bull.
>

There are a lot of misconceptions about what capacitors are, what they do, and
what to look for in one. A capacitor will not make your system suddenly sound
much louder (although it can improve it slightly). It will not increase the
voltage in your cars system (but it will help maintain it). A capacitor will
not provide extra power for devices (but it will maintain it). A capacitor,
however, will provide a benefit for most audiophiles in overall sound quality,
and can benefit your cars electrical system.

For starters, a capacitor has a specific construction. The most basic form of
a capacitor is two metal plates, which are very close to each other, but do
not touch. The plates are separated by some type of insulating material. Air,
which does not conduct, can be used as an insulator, and on older AM/FM
radios, the tuning capacitor uses air. Other materials can be used, like
plastics, or electrolyte pastes. When power is applied to the capacitor, the
charges flow from positive, to the positive plate of the capacitor. The
charges stop at the one plate, because of the insulating material, but the
electrostatic charge pushes against the charge of the other plate, and causes
the current to flow on that side. This flow will happen as long as the charges
are able to build up on the plates. The size of the plate, and the distance
between the two plates will determine how much charge the plates can hold.
When the power source is removed, the charges are still there, and they have
no place to go. The charges would like to meet each other, to equalize the
charges between the two plates, but the insulator between the plates prevent
this. If the plates were allowed to touch, the charges would all flow to the
other side at once (which could be very dangerous). If some device, such as a
light bulb, speaker, or motor were used to bridge the two sides of the
capacitor, the charges would power that device until both plates evened out
their charges. In this manner, a capacitor stores electrical charge.

When a capacitor charges, it does so at a certain rate. Normally, a capacitor
will try to take as much charge as it possibly can, as quickly as it can. Like
the shorting of a capacitor, this can be very dangerous. When installing a
power supply capacitor (often called a stiffening cap) in a car, you should
always charge it through a resistor. A resistor will slow down the rate at
which the capacitor charges or discharges. This is known as an RC time
constant. This is useful when a capacitor is used for audio. As I said
earlier, current will flow through a capacitor until it is saturated. The
speed at which a capacitor can take on a charge, and let it out is the
frequency at which that capacitor prefers to work. Capacitors, to a certain
degree, will resist lower frequencies than it can handle, but will present
very little resistance at higher frequencies. This makes small capacitors
ideal for blocking low frequency bass from speakers which cannot handle them
(you are probably familiar with these as "bass blockers"). The property where
a capacitor has more resistance to lower frequencies is called Capacitive
Reactance. There is a neat formula for it too, its like this:



Xc=1/(2 PI FC)

Where Xc is Capacitive reactance. PI is 22/7, or more commonly used
3.1415..... F is frequency, and C is the capacitance in farads, . Now since a
farad of charge is highly impractical for audio uses, you will have to convert
the rating on your capacitor (which is usually in microfarads, or "µf") to a
decimal equivalent of a farad. The easiest way to do this, of course, is to
move the decimal point to the left.

Anyway....

When a resistor is placed in series with a capacitor, it will change the
characteristics of the capacitor, with respect to its reactance. For most car
applications, that resistance is the speaker it is used on.

Knowing this, we want to look at the two applications of capacitors for car
audio:

Power Supply Stabilization
Crossovers


Very large capacitors are used for stabilizing the electrical system. As we
have seen, a capacitor stores energy. In a system where several electrical
devices are competing for power, when an amp starts using power at an
inconstant rate (a little here, a little there), head and dash lights begin to
dim. This can also affect other amps in the system. Amps have internal
capacitors on the other side of their power supply which hold power for those
times when it is really needed. However, the power to charge those capacitors
has to come from somewhere, and during peak usage, the power is not always
available. The result is that the distortion in the music increases slightly:
Sound suffers. A capacitor will store the energy, and will give the energy up
when it is needed by other components.

Another benefit of the large capacitor, is that as we mentioned, it passes
high frequencies. Any electrical noise will be filtered by a capacitor since
the noise is AC. In addition, since the capacitor is a large one, then the
"high" frequency can actually be pretty low. In this manner, a capacitor helps
reduce power supply noise in your audio system. Unfortunately, the larger
capacitors are usually polar, meaning that they have a + and - side, and do
not work properly when working backwards. The saving grace here is that, even
in reverse, there is some capacitance, just not as much as when polarity is
respected.

The second use of a capacitor in car audio, is as a crossover. As we've seen
earlier, the capacitor (smaller, non polar ones) will pass AC of higher
frequencies, and resist lower ones. Bass blockers are one example of this.
When capacitors are used along with coils, they form crossover networks, which
improve the sound going to a driver, and can make a speaker system sound a lot
better. Many component sets have crossovers, which use a capacitor to carry
the + signal* to the tweeter, and a coil would carry the + signal to the
woofer. The negative signals do not need the components, because as long as
the capacitor (or coil) are in the circuit somewhere, they will do their job.
Without the coil and capacitors, the tweeter would distort badly, the woofer
would usually do a really bad job of reproducing the highs, and there would be
a nasty peak where the woofer and tweeter overlap.

Finally, capacitors can serve several other functions. Getting back to the RC
time constant, you could use a capacitor to do things such as allow lights to
"fade out" when you turn them off, or to charge a relay for keeping power to
your system until you arm the alarm/open the door. You can even make a buzzer
from a small capacitor and a relay. The applications are endless if you use
your imagination.

[Mark Zarella]

> >I know of no practical applications where a capacitor is a more viable
> >option, aside from trying to prevent dimming by putting them as close to
> >the headlights as possible. Yet the reasons most often attributed to
> >adding capacitance tend to be to improve sound in some fashion by
> >mounting them as close to the amplifiers as possible - total bull.
> >
>
> There are a lot of misconceptions about what capacitors are, what they do,
and
> what to look for in one. A capacitor will not make your system suddenly
sound
> much louder (although it can improve it slightly).

Slightly? Maybe. But not even close to being detectable by the ear.

> It will not increase the
> voltage in your cars system (but it will help maintain it). A capacitor
will
> not provide extra power for devices (but it will maintain it). A
capacitor,
> however, will provide a benefit for most audiophiles in overall sound
quality,
> and can benefit your cars electrical system.

How does it benefit sound quality?

<snip review, which is very well written and technically precise, by the
way>

> Very large capacitors are used for stabilizing the electrical system. As
we
> have seen, a capacitor stores energy. In a system where several electrical
> devices are competing for power, when an amp starts using power at an
> inconstant rate (a little here, a little there), head and dash lights
begin to
> dim. This can also affect other amps in the system. Amps have internal
> capacitors on the other side of their power supply which hold power for
those
> times when it is really needed. However, the power to charge those
capacitors
> has to come from somewhere, and during peak usage, the power is not always
> available. The result is that the distortion in the music increases
slightly:
> Sound suffers. A capacitor will store the energy, and will give the energy
up
> when it is needed by other components.

Distortion increases *slightly*. Yeah, this is due to a slight sag in the
rail voltage corresponding to the current draw. Yet the difference in rail
voltage between the external cap case and the non-cap case is too small to
cause a change in the output to make it detectable by humans. I can
demonstrate this to you mathematically if you prefer. The proof is based on
the assumption that detection threshold changes in the typical musical
spectrum at typical SPL levels is at the very least 0.5 dB (that's a low
estimate). Then you simply do the electrical analysis, taking amplifier
output impedance, global NFB, and speaker impedance into account. I've done
these calculations in here before. You can try to google them up if you'd
like. The net result was that the difference between having a cap and not
having one tended to be well below threshold.

> Another benefit of the large capacitor, is that as we mentioned, it passes
> high frequencies. Any electrical noise will be filtered by a capacitor
since
> the noise is AC.

Electrical noise is filtered "better" by the smaller capacitors inside the
amplifier. Why? Lower net ESL.

> In addition, since the capacitor is a large one, then the
> "high" frequency can actually be pretty low. In this manner, a capacitor
helps
> reduce power supply noise in your audio system.

Very low frequency noise is never an issue.

<snip crossover stuff>

[Scott Gardner]

On Mon, 01 Dec 2003 13:25:53 GMT, Mark Zarella
> wrote:

>>Batteries do in fact supply current to the audio system. Try running a
>>>system with the car on and the battery disconnected. Oftentimes the
>>>amplifiers will shut off due to voltage below threshold. In addition, a
>>>poor battery will draw excess current from the alternator when charging.
>>> This also has a detrimental effect.
>>>
>>
>> I agree that the battery will provide current when the
>> alternator cannot keep up with the load. Unfortuneately, the battery
>> is a poor candidate for this job, since it has a relatively high
>> internal resistance. This resistance, combined with a high current
>> drain, will cause a significant voltage drop. This is why it's
>> acceptable for even a "good" battery to drop from 12V all the way down
>> to 9.6V while cranking over the engine.
>> Capacitors have a MUCH small internal resistance, so they can
>> provide a larger surge of current without a corresponding large
>> voltage drop.
>
>Batteries are an integral part of the audio system. Certainly moreso
>than a capacitor. The benefits of added capacitance do not
>significantly contribute to the alternator's net output. The same
>cannot be said of batteries. Although the output impedance of a battery
>is greater than that of a capacitor, the amount of energy it stores and
>therefore can deliver is much greater. Capacitors are useless for
>trying to keep up with musical transients, which tend to last longer
>than the usable discharge time of a 1 to few farad capacitor.
>
Let me start off by saying that Captain Howdy and I are approaching
this from two different angles. All I am saying is that in the
specific case where your alternator is keeping up with the *average*
electrical requests from your car's accessories, but you're getting a
little flickering of your lights during transients, a capacitor placed
in parallel to the battery can eliminate that flickering. I'm making
no claims as to whether it will make your system "louder", "cleaner",
or anything of the sort. I'm not even saying there will be an audible
difference at all. I've never heard one myself.

>>>The voltage drop is proportional to the time. That means that there's
>>>ALWAYS a voltage drop as the capacitor discharges, and it can become
>>>quite substantial for "typical" (whatever that is) transients. This can
>>>all be verified with mathematics also.
>>
>>
>> Again, you're absolutely right. There is a voltage drop across the
>> capacitor's terminals as a load is applied, but we can vary how
>> quickly the voltage drops by varying the capacitance. Depending on
>> our needs for a particular installation, we can make the discharge
>> time constant equal to whatever we want by using smaller or larger
>> capacitors.
>
>Yeah, and for practical applications, this requires a pretty huge amount
>of capacitance. And for what benefit?

It's not a huge amount at all. I've eliminate flickering lights with
as little as 1/4-Farad of added capacitance. As for the benefit, it's
like I said above - I make no claims as to the usefulness of
capacitors except that it can smooth out transients enough to help
with flickering headlamps or dash lighting.

>
>>>> As long as your
>>>>alternator can handle your car's average current requirements, it's
>>>>not a "band-aid" or bad engineering to use a capacitor to handle the
>>>>transients.
>>>
>>>The engineers already put them inside the amp. Are you suggesting their
>>>engineering is inadequate?
>>>
>>
>> I think the engineers do the best they can within the
>> constraints of packaging size, cost, and the fact that they can't
>> predict how exactly the amp will be used. They don't know how much
>> capacity your car's alternator has, or what other loads are sharing
>> that capacity.
>> My guidance is that unless you know for certain that
>> your stock alternator isn't up to the task (like trying to put 3000
>> watts of amplification in a stock Civic), give it a try without
>> upgrading the alternator or adding a capacitor. If you can drive
>> around all day playing music at your normal levels without discharging
>> the battery, then your alternator is obviously capable of handling the
>> *average* load you're putting on it.
>
>If your battery is discharging, there's no amount of capacitance that
>will help.

That's exactly what I said. If your battery is discharging over a
long period of time, the solution is not a capacitor - it's a
higher-capacity alternator.

>
>> At this point, either
>> everything's good, or you're getting some dimming of lights during
>> large transients. Now, I would try a capacitor. Start off with the 1
>> Farad/kW estimate and go from there. If that still doesn't solve the
>> problem, you have to find out which is cheaper - more capacitance, or
>> a higher-capacity alternator. Some applications are cheap - you can
>> get 150A alternators for Hondas for less than $250. For older or more
>> offbeat cars, the choices are slimmer.
>> I'm not saying that every installation needs a capacitor, and
>> I'll admit that beyond a certain point, it becomes more cost-effective
>> to put in a higher-capacity alternator. I'm just responding to the
>> people that make blanket statements like "capacitors suck", or blindly
>> follow rules-of-thumb like "one Farad per 1,000 watts amplifier
>> power".
>
>I know of no practical applications where a capacitor is a more viable
>option, aside from trying to prevent dimming by putting them as close to
>the headlights as possible. Yet the reasons most often attributed to
>adding capacitance tend to be to improve sound in some fashion by
>mounting them as close to the amplifiers as possible - total bull.

I've never made such claims about the audio benefits of capacitors -
you must have me confused with someone else. All I've been saying
from the beginning is that in cases where your alternator can handle
the *average* load presented to it, but you're getting some flickering
of your lights during transients, a capacitor is an acceptable
solution vice upgrading to a higher-capacity alternator.

Scott Gardner

[Mark Zarella]

> >Batteries are an integral part of the audio system. Certainly moreso
> >than a capacitor. The benefits of added capacitance do not
> >significantly contribute to the alternator's net output. The same
> >cannot be said of batteries. Although the output impedance of a battery
> >is greater than that of a capacitor, the amount of energy it stores and
> >therefore can deliver is much greater. Capacitors are useless for
> >trying to keep up with musical transients, which tend to last longer
> >than the usable discharge time of a 1 to few farad capacitor.
> >
> Let me start off by saying that Captain Howdy and I are approaching
> this from two different angles. All I am saying is that in the
> specific case where your alternator is keeping up with the *average*
> electrical requests from your car's accessories, but you're getting a
> little flickering of your lights during transients, a capacitor placed
> in parallel to the battery can eliminate that flickering. I'm making
> no claims as to whether it will make your system "louder", "cleaner",
> or anything of the sort. I'm not even saying there will be an audible
> difference at all. I've never heard one myself.

Then we're in agreement.


> >I know of no practical applications where a capacitor is a more viable
> >option, aside from trying to prevent dimming by putting them as close to
> >the headlights as possible. Yet the reasons most often attributed to
> >adding capacitance tend to be to improve sound in some fashion by
> >mounting them as close to the amplifiers as possible - total bull.
>
> I've never made such claims about the audio benefits of capacitors -
> you must have me confused with someone else.

Sorry. I wasn't referring to you specifically.

[Aaron]

>>much louder (although it can improve it slightly).
> Slightly? Maybe. But not even close to being detectable by the ear.

Not really, I didn't expect any volume increase when I installed my caps.

> How does it benefit sound quality?

By smoothing out the voltage in the car, the caps ensure the head unit,
as well as the rest of the car, has proper voltage more often. A head
unit will sound a lot better running at 14 v than 11.5 volts.


Personally I use caps because I don't want to burn out my alt. If you
expect your alternator to give you 100 amp power spikes reliably, you
gotta check out the small leads connected to the brushes. I want my
alternator running as constantly as possible. If I can make it so that
it runs at a constant 40 amps, and the caps handle the 100 amp spikes
and 10 amp lows, then my alt is going to be a lot happier.

Anyway I don't want to beat an old horse here, just adding my educated
$.02 to the mix ;)

Cheers,

Aaron

[Soundfreak03]

> How does it benefit sound quality?
>
>By smoothing out the voltage in the car, the caps ensure the head unit,
>as well as the rest of the car, has proper voltage more often. A head
>unit will sound a lot better running at 14 v than 11.5 volts.
>

A cap will not take a system running 11.5 volts and smooth it out to 14. Are
you sure you even know what a cap is and does?

>Personally I use caps because I don't want to burn out my alt. If you
>expect your alternator to give you 100 amp power spikes reliably, you
>gotta check out the small leads connected to the brushes. I want my
>alternator running as constantly as possible.

A cap is not going to help your alt. IF your alt is burning out then
capacitance is not the issue.

>If I can make it so that
>it runs at a constant 40 amps, and the caps handle the 100 amp spikes
>and 10 amp lows, then my alt is going to be a lot happier.
>

WTF?? What are you talking about?

>Anyway I don't want to beat an old horse here, just adding my educated
>$.02 to the mix ;)
>

No offense Aaron but you educated 2 cents needs to get its ass back into school
and learn what a cap is and does. It is not a wonder fix it all make a system
sound better as you imply. In most cases it is at BEST a bandaid and at worse a
detriment to the system.

Les

[Mark Zarella]

> > How does it benefit sound quality?
>
> By smoothing out the voltage in the car, the caps ensure the head unit,
> as well as the rest of the car, has proper voltage more often. A head
> unit will sound a lot better running at 14 v than 11.5 volts.

How??

[Aaron]

>>By smoothing out the voltage in the car, the caps ensure the head unit,
>>as well as the rest of the car, has proper voltage more often. A head
>>unit will sound a lot better running at 14 v than 11.5 volts.
>
>
> How??

The same reason as the amps do, higher voltage to the head unit will
ensure it doesn't have to work as hard to make the same sound, and it
will reduce distortion near the limit.

If you guys disagree with this I really should just leave this NG...

Aaron

[Soundfreak03]

>>>By smoothing out the voltage in the car, the caps ensure the head unit,
>>>as well as the rest of the car, has proper voltage more often. A head
>>>unit will sound a lot better running at 14 v than 11.5 volts.
>>
>>
>> How??
>
>The same reason as the amps do, higher voltage to the head unit will
>ensure it doesn't have to work as hard to make the same sound, and it
>will reduce distortion near the limit.

If your not running into clipping it will sound the same. Regardless of the
voltage. Assuming reasonable levels.


>
>If you guys disagree with this I really should just leave this NG...
>
>Aaron

Well bye. I see your logic but it has an inherent flaw. It will only be able to
get louder without distortion, which is not better sound, just louder without
distortion.

Les

[Aaron]

> If your not running into clipping it will sound the same. Regardless of the
> voltage. Assuming reasonable levels.

True. But at reasonable listening levels I'm not getting voltage drop
either. The only time I'll get voltage drop is at 10/10ths, and that's
when my head unit might run into clipping.

[Soundfreak03]

>> If your not running into clipping it will sound the same. Regardless of the
>> voltage. Assuming reasonable levels.
>
>True. But at reasonable listening levels I'm not getting voltage drop
>either. The only time I'll get voltage drop is at 10/10ths, and that's
>when my head unit might run into clipping.

Nontheless your SQ will not change up to the point of clipping. The unit may be
able to play LOUDER, but that is not the same thing as it sounding better. It
will have the same SQ but just get louder. Make sense?

Les

[GregS]

In article >, Aaron > wrote:
>>>much louder (although it can improve it slightly).
>> Slightly? Maybe. But not even close to being detectable by the ear.
>
>Not really, I didn't expect any volume increase when I installed my caps.
>
>> How does it benefit sound quality?
>
>By smoothing out the voltage in the car, the caps ensure the head unit,
>as well as the rest of the car, has proper voltage more often. A head
>unit will sound a lot better running at 14 v than 11.5 volts.
>
>
>Personally I use caps because I don't want to burn out my alt. If you

I don't think caps help an alternator last longer. But I have not tested that
really. But a cap does help an alternator and the wiring losses. An alternator must
be running at high RPM to come close to its rated capacity. Even if
your driving down the road it may not be running fast enough to put out 100% capacity.
A cap does help maintain a voltage closer to the alternator rather than the battery.

greg

[Tha Ghee]

"Aaron" > wrote in message
...
> >>By smoothing out the voltage in the car, the caps ensure the head unit,
> >>as well as the rest of the car, has proper voltage more often. A head
> >>unit will sound a lot better running at 14 v than 11.5 volts.
> >
> >
> > How??
>
> The same reason as the amps do, higher voltage to the head unit will
> ensure it doesn't have to work as hard to make the same sound, and it
> will reduce distortion near the limit.
>
> If you guys disagree with this I really should just leave this NG...
>
> Aaron
>
your speaking of if you have more input voltage you need less current which
puts less stress on the HU/amp components