Should I get a cap for my JL Audio 500/1?
#1
01-16-2010, 05:52 PM
Should I get a cap for my JL Audio 500/1?
I am piecing together my system and was curious if I should pick up a capacitor before having everything installed. I will be running a JL Audio 10W6 in a 1080 box with a JL Audio 500/1 v2 amp. Do you think this will be necessary? I was thinking of going for a 1 or 1.5 farad cap...not really sure if I would need a 2 farad. Let me know what you think. Thanks!!
#2
01-16-2010, 08:48 PM
Nope.
Waste of money, but they look cool. There's some well-written stuff by actual electrical engineers out there:
http://www.teamswift.net/viewtopic.php?p=54856
http://www.welcometotheden.8k.com/caraudio/Captest.pdf (this one hast to be manually pasted into the address bar for some people)
Spend the money towards larger-gage wiring, a higher-output alternator or an optima yellow-top. Unless you want them for looks.
Waste of money, but they look cool. There's some well-written stuff by actual electrical engineers out there:
http://www.teamswift.net/viewtopic.php?p=54856
http://www.welcometotheden.8k.com/caraudio/Captest.pdf (this one hast to be manually pasted into the address bar for some people)
Spend the money towards larger-gage wiring, a higher-output alternator or an optima yellow-top. Unless you want them for looks.
#3
01-16-2010, 11:24 PM
Nope.
Waste of money, but they look cool. There's some well-written stuff by actual electrical engineers out there:
http://www.teamswift.net/viewtopic.php?p=54856
http://www.welcometotheden.8k.com/caraudio/Captest.pdf (this one hast to be manually pasted into the address bar for some people)
Spend the money towards larger-gage wiring, a higher-output alternator or an optima yellow-top. Unless you want them for looks.
Waste of money, but they look cool. There's some well-written stuff by actual electrical engineers out there:
http://www.teamswift.net/viewtopic.php?p=54856
http://www.welcometotheden.8k.com/caraudio/Captest.pdf (this one hast to be manually pasted into the address bar for some people)
Spend the money towards larger-gage wiring, a higher-output alternator or an optima yellow-top. Unless you want them for looks.
#4
01-16-2010, 11:25 PM
#5
01-16-2010, 11:26 PM
#6
01-17-2010, 09:47 PM
#7
01-17-2010, 10:31 PM
They're designed to compensate for a lack of power from the charging system, however, the amount of power above the 12+ volts from the battery they provide is miniscule.
Read through the links I provided and tell me of a more scientific test (electricity and power output is science, btw) to measure where the effects of a capacitor would be beneficial. Capacitors have their places where an instantaneous discharge is required, such as a camera flash, but the thump from a sub is far from instantaneous, require a push, not a sharp stab.
I will agree though, they do look cool, especially with the digital volt readouts on them, and they don't hurt anything either, but I wouldn't spend my money on them.
Read through the links I provided and tell me of a more scientific test (electricity and power output is science, btw) to measure where the effects of a capacitor would be beneficial. Capacitors have their places where an instantaneous discharge is required, such as a camera flash, but the thump from a sub is far from instantaneous, require a push, not a sharp stab.
I will agree though, they do look cool, especially with the digital volt readouts on them, and they don't hurt anything either, but I wouldn't spend my money on them.
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#8
01-18-2010, 12:21 AM
They're designed to compensate for a lack of power from the charging system, however, the amount of power above the 12+ volts from the battery they provide is miniscule.
Read through the links I provided and tell me of a more scientific test (electricity and power output is science, btw) to measure where the effects of a capacitor would be beneficial. Capacitors have their places where an instantaneous discharge is required, such as a camera flash, but the thump from a sub is far from instantaneous, require a push, not a sharp stab.
I will agree though, they do look cool, especially with the digital volt readouts on them, and they don't hurt anything either, but I wouldn't spend my money on them.
Read through the links I provided and tell me of a more scientific test (electricity and power output is science, btw) to measure where the effects of a capacitor would be beneficial. Capacitors have their places where an instantaneous discharge is required, such as a camera flash, but the thump from a sub is far from instantaneous, require a push, not a sharp stab.
I will agree though, they do look cool, especially with the digital volt readouts on them, and they don't hurt anything either, but I wouldn't spend my money on them.
I do have some issue with a lot of the Richard Clark references people throw around. Like the article where he bashes caps in the ground (many years ago) and then comes back a couple years later with his own cap through Monster. In the second link you sent with the 15F cap, a cap like that would have a very high ESR and not very suitable for car audio. That article is also 10 years old now.
I understand that electricity and power output are science, I am an electrical engineer that designs power amplifers (RF, not car audio).
#9
01-20-2010, 02:37 AM
#10
01-20-2010, 10:44 AM
Damn. I really love these discussions on caps. So much misinformation in them, even from people claiming to be seasoned engineers.
Those caps, when properly used, are only to provide the initial inrush of current to the amplifier during a peak transient condition (large bass hit for example) that the battery / cabling is unable to provide. Basically just a large bypass capacitor.
The connections between amplifier and the battery / alternator in the front of the car has a LOT of inductance and if we recall Electronics 101, we know that any instantaneous change in current in an inductor is not possible - it always ramps up at some rate. So, during a peak transient hit, REGARDLESS of the capacity of the battery (front of car) or alternator, there is a limit to how much peak current can be delivered during the transient.
This is where the capacitor comes in. It will deliver that peak transient energy, but its only a very tiny bit, and then during the OFF time (no transient peaks), the alternator will recharge that capacitor. Its just an energy resevoir, nothing else.
Of course, its also important to note that the right kind of capacitor needs to be used as well. It needs ultra low ESR / ESL to work properly, otherwise its not doing anything - which is basically what happens with "el cheapo" caps on the market.
For those who are electrically disadvantaged, the mechanical example should clear it up.
Take a toilet. When you flush a toilet, there isn't enough water pressure in the water line to perform the actual flush (peak transient condition). Therefore, there is an resevoir (capacitor) in the top of the toilet to store water until its needed for a flush event. Once the transient (flush) is completed, the water from the water line will slowly recharge the resevoir tank (capacitor). Same thing with the audio amplifier and capacitor - of course, the time scale is vastly reduced.
But whether its really necessary depends on the system and amplifier. Amplifiers have their own energy storage capacitors inside them to begin with and most of the time, that is sufficient enough for most transients.
Those caps, when properly used, are only to provide the initial inrush of current to the amplifier during a peak transient condition (large bass hit for example) that the battery / cabling is unable to provide. Basically just a large bypass capacitor.
The connections between amplifier and the battery / alternator in the front of the car has a LOT of inductance and if we recall Electronics 101, we know that any instantaneous change in current in an inductor is not possible - it always ramps up at some rate. So, during a peak transient hit, REGARDLESS of the capacity of the battery (front of car) or alternator, there is a limit to how much peak current can be delivered during the transient.
This is where the capacitor comes in. It will deliver that peak transient energy, but its only a very tiny bit, and then during the OFF time (no transient peaks), the alternator will recharge that capacitor. Its just an energy resevoir, nothing else.
Of course, its also important to note that the right kind of capacitor needs to be used as well. It needs ultra low ESR / ESL to work properly, otherwise its not doing anything - which is basically what happens with "el cheapo" caps on the market.
For those who are electrically disadvantaged, the mechanical example should clear it up.
Take a toilet. When you flush a toilet, there isn't enough water pressure in the water line to perform the actual flush (peak transient condition). Therefore, there is an resevoir (capacitor) in the top of the toilet to store water until its needed for a flush event. Once the transient (flush) is completed, the water from the water line will slowly recharge the resevoir tank (capacitor). Same thing with the audio amplifier and capacitor - of course, the time scale is vastly reduced.
But whether its really necessary depends on the system and amplifier. Amplifiers have their own energy storage capacitors inside them to begin with and most of the time, that is sufficient enough for most transients.
#11
09-12-2012, 01:42 AM
For those who are electrically disadvantaged, the mechanical example should clear it up.
Take a toilet. When you flush a toilet, there isn't enough water pressure in the water line to perform the actual flush (peak transient condition). Therefore, there is an resevoir (capacitor) in the top of the toilet to store water until its needed for a flush event. Once the transient (flush) is completed, the water from the water line will slowly recharge the resevoir tank (capacitor). Same thing with the audio amplifier and capacitor - of course, the time scale is vastly reduced.
But whether its really necessary depends on the system and amplifier. Amplifiers have their own energy storage capacitors inside them to begin with and most of the time, that is sufficient enough for most transients.
Think of a capacitor like shock absorber in your suspension. The alternator and battery are part of the equation also, but the cap is what helps to smooth everything out. The bumps on the ground are like the power consumed by lights, amps, etc.. the feel of the ride inside the car is like what the alternator needs to produce.
As you go over mild bumps in your G, the car will 'float' or 'bump' up and down a little depending on the stiffness of your ride and the roughness of the road as the wheels 'instantaneously' move up and down to the road underneath because of the shock absorbers, springs, and inertia of the car but at the basic level the shocks keep the ride as smooth as possible.
Feeling hard bumps while on the freeway = lights dimming.
Minor up and downs and occasional road noise = perfectly normal.
Just like you are cautious about the surfaces on which you drive your sports car, you need to be mindful of the load you place on your electrical system.
As you upgrade your suspension - for example, think Baja 1000 pre-runner - you can float over 1 or 2 foot ruts or woop sections, traveling at 80-100mph, drinking a cup of hot coffee in the passenger seat not feeling a thing. Yes, by all means the suspension is working *very* hard, and boy it sure is expensive.. but you dont have to keep slowing down to drink your coffee. Caps, alternators, and batteries can be expensive.. but your lights dimming sure does look ghetto if your electrical system configuration can't keep up with the load you're applying to it.
#12
09-12-2012, 02:12 AM
^ This is all great for how people want them to work, and how they're sold, but electricity, current and power draw is a very scientific thing that can be measured, so whatever good you think it could do can be measured as well.
So instead of being a shock absorber on your truck, the capacitor is a lot more like sitting on a centimeter of foam in your seat. After everything else has done its best to keep everything smooth, it might just do a little something extra.
And for more in-depth reading: http://www.welcometotheden.8k.com/caraudio/Captest.pdf (you must copy and paste this link, clicking it doesn't work)
Why caps don't do much good - the extremely short and basic version.
Let's imagine a car with a 12v battery and an alternator putting out 14v. This car also has a 1000watt amp powering some random sub.
We now add a 1 farad capacitor.
A 1 farad cap charged to 14v stores about 84 joules.
Since we have the battery sitting at 12v, the potential (usable power) of the cap is 2v or 12 joules.
We CANNOT use more than the 12 joules, since that would put the cap below the magical 12v where the battery kicks in.
In order to use the power stored in the cap, we would have to turn off the alternator, or the power it outputs would somehow have to drop - like if it's overloaded (BAD).
Note: 1 joule = 1 watt-second. 1000w for one second is 1000 joule.
Anyway, our 1 farad cap has 12 joules of power we can actually use. this translates into 12 watt-seconds. This can power our 1000w amp for 12/1000s of a second, or 0.012seconds.
This means that if we charge the cap to 14v, and turn off the alternator, we can play a single test tone of 83hz one single time before the cap becomes useless.
Since I'm not at all an expert on this, I have neglected to mention ESR and ESL, which would significantly reduce the benefit we get from the cap.
Because of ESR (ElectroStatic Resistance), an amount of power will be converted into heat in the cap. The more power you try to pull, the more heat and the less useful it is.
Additionally, the amp will convert some amount of power into heat - all depending on the amp.
In the end, the cap may give us as much as .005 seconds (single 200hz tone) of power at 1000w amp output, IF the alternator suddenly dies or for some magical reason (it's overloaded, duh) it drops it's output to 12v. If you only run 500W, it would be about 0.01 second or a single 100hz test tone.
Let's imagine a car with a 12v battery and an alternator putting out 14v. This car also has a 1000watt amp powering some random sub.
We now add a 1 farad capacitor.
A 1 farad cap charged to 14v stores about 84 joules.
Since we have the battery sitting at 12v, the potential (usable power) of the cap is 2v or 12 joules.
We CANNOT use more than the 12 joules, since that would put the cap below the magical 12v where the battery kicks in.
In order to use the power stored in the cap, we would have to turn off the alternator, or the power it outputs would somehow have to drop - like if it's overloaded (BAD).
Note: 1 joule = 1 watt-second. 1000w for one second is 1000 joule.
Anyway, our 1 farad cap has 12 joules of power we can actually use. this translates into 12 watt-seconds. This can power our 1000w amp for 12/1000s of a second, or 0.012seconds.
This means that if we charge the cap to 14v, and turn off the alternator, we can play a single test tone of 83hz one single time before the cap becomes useless.
Since I'm not at all an expert on this, I have neglected to mention ESR and ESL, which would significantly reduce the benefit we get from the cap.
Because of ESR (ElectroStatic Resistance), an amount of power will be converted into heat in the cap. The more power you try to pull, the more heat and the less useful it is.
Additionally, the amp will convert some amount of power into heat - all depending on the amp.
In the end, the cap may give us as much as .005 seconds (single 200hz tone) of power at 1000w amp output, IF the alternator suddenly dies or for some magical reason (it's overloaded, duh) it drops it's output to 12v. If you only run 500W, it would be about 0.01 second or a single 100hz test tone.
And for more in-depth reading: http://www.welcometotheden.8k.com/caraudio/Captest.pdf (you must copy and paste this link, clicking it doesn't work)
Last edited by Wrathernaut; 09-12-2012 at 02:24 AM.
