If you have any headlight flicker, you definitely need a cap. If not, it's your call. It is probably easier on the alternator to have one. A good amp will already have more capacitance built in than a cheap amp, so that's also a factor. I've never used a cap on my mild systems, which have always been powered by my old 200W RMS Alpine V12.
car amplifiers and capacitors.......
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People are thinking the caps are just for long-term energy storage... they're usually to absorb instantaneous demand on a subwoofer for individual bass.
definitely, the installer in sault ontario has another BATTERY to supply the peak power. this is not a crazy guy who does something for nothing. putting in the capacitor does the same job, but in a smaller cheaper package. 500 microfarad is 1/2 of a farad, which is a nice hefty number of electrons. the capacitor acts as a reservoir - at all times, the reservoir is filling, until it is full. when a peak comes along, the electrons are released to the amplifier, draining the capacitor, but not emptying it completely. after the peak is over, the capacitor fills again. it acts just the same as a reservoir of water before a hydroelectric dam. bass uses a lot of current, and you can supply this current with lighter guage of wire if you have a capacitor right next to the amp. this is very simple.
also, we are dealing with DC, not AC, so there is no phase shift.
also, we are dealing with DC, not AC, so there is no phase shift.
I would like to know what the manufacturers of these amplifiers say about adding a capacitor... I would think that if they were required, they would either ship with the amp or a reference made in the operators manual about it.
I always used Slick50 and believed it helped too ....
Originally Posted By: Patman
.... the biggest of which is a P500 which is currently putting out almost 700 watts RMS.
700 watts RMS output is about a kilowatt peak, and would require 71 amps at 14 volts, assuming the amp is 100% efficient. AFAIK, even the best switchers can only do around 90% efficiency, so an amp of that actual power capability probably needs at least 80 amps and maybe a lot more. That's a lot of current, and assumes no voltage drop.
If these car audio devices actually put out the power they claim ( does anybody actually measure these things? ), I can't see capacitors being of any value at these current levels.
I would use a large battery right at the output device, and 4 to 6 gauge wiring on both positive and negative leads, depending on distance, to the main power source.
.... the biggest of which is a P500 which is currently putting out almost 700 watts RMS.
700 watts RMS output is about a kilowatt peak, and would require 71 amps at 14 volts, assuming the amp is 100% efficient. AFAIK, even the best switchers can only do around 90% efficiency, so an amp of that actual power capability probably needs at least 80 amps and maybe a lot more. That's a lot of current, and assumes no voltage drop.
If these car audio devices actually put out the power they claim ( does anybody actually measure these things? ), I can't see capacitors being of any value at these current levels.
I would use a large battery right at the output device, and 4 to 6 gauge wiring on both positive and negative leads, depending on distance, to the main power source.
Patman
Staff member
Originally Posted By: Win
If these car audio devices actually put out the power they claim ( does anybody actually measure these things? )
Actually yes. Every Fosgate amp is bench tested and a complete printout is included in the box. I said mine had "almost 700 watts" but I believe the actual number printed on my sheet was around 667 watts RMS. Fosgate under rates their amplifiers, they always put out more power than they are supposed to.
If these car audio devices actually put out the power they claim ( does anybody actually measure these things? )
Actually yes. Every Fosgate amp is bench tested and a complete printout is included in the box. I said mine had "almost 700 watts" but I believe the actual number printed on my sheet was around 667 watts RMS. Fosgate under rates their amplifiers, they always put out more power than they are supposed to.
I was going to post what Win said, I would invest in another battery rather than a large capacitor.
When the auto engineers designed the electrical system in the vehicle I don't think they took into consideration (nor should they have to) that some "audiophile" was going to add 1,000 watt audio amps to the circuitry.
We all see examples of "A little knowledge is a dangerous thing" scenarios. I will go back to my previous question... what does the amp manufacturer say about extra batteries/capacitors/wiring gage ??....
I have seen many power amps with a 1-10 volume control that was useless/dangerous after "7" because it was clipping. So, in reality, it only had a 1-7 volume control.
When the auto engineers designed the electrical system in the vehicle I don't think they took into consideration (nor should they have to) that some "audiophile" was going to add 1,000 watt audio amps to the circuitry.
We all see examples of "A little knowledge is a dangerous thing" scenarios. I will go back to my previous question... what does the amp manufacturer say about extra batteries/capacitors/wiring gage ??....
I have seen many power amps with a 1-10 volume control that was useless/dangerous after "7" because it was clipping. So, in reality, it only had a 1-7 volume control.
Patman
Staff member
Originally Posted By: Papa Bear
I was going to post what Win said, I would invest in another battery rather than a large capacitor.
A second battery is definitely a good idea for a high powered system, but in a car like my Corvette space is a big issue so it's much easier to add a small cap then a second battery.
I was going to post what Win said, I would invest in another battery rather than a large capacitor.
A second battery is definitely a good idea for a high powered system, but in a car like my Corvette space is a big issue so it's much easier to add a small cap then a second battery.
Here is a pretty fair article on caps. Iv'e fiddled with them in my sons cars (I too old for that type of volume).
http://www.caraudiohelp.com/newsletter/car_audio_capacitor_myth.htm
Switch mode power supplies and charging systems cannot respond fast enough to keep the voltage from sagging. If the headlights dim (fairly local to the source), then no wire size in the world will help. Switch Mode power supplies are not known for their fast transient response, linears respond faster. Old discrete amps used to have huge storage caps internal to them for this purpose.
Good info from Rockford Fosgate
http://www.rockfordfosgate.com/scripts/rightnow.cfg/php.exe/enduser/std_adp.php?p_faqid=145
http://www.caraudiohelp.com/newsletter/car_audio_capacitor_myth.htm
Switch mode power supplies and charging systems cannot respond fast enough to keep the voltage from sagging. If the headlights dim (fairly local to the source), then no wire size in the world will help. Switch Mode power supplies are not known for their fast transient response, linears respond faster. Old discrete amps used to have huge storage caps internal to them for this purpose.
Good info from Rockford Fosgate
http://www.rockfordfosgate.com/scripts/rightnow.cfg/php.exe/enduser/std_adp.php?p_faqid=145
Last edited:
Originally Posted By: JetStar
Here is a pretty fair article on caps. Iv'e fiddled with them in my sons cars (I too old for that type of volume).
http://www.caraudiohelp.com/newsletter/car_audio_capacitor_myth.htm
Switch mode power supplies and charging systems cannot respond fast enough to keep the voltage from sagging. If the headlights dim (fairly local to the source), then no wire size in the world will help. Switch Mode power supplies are not known for their fast transient response, linears respond faster. Old discrete amps used to have huge storage caps internal to them for this purpose.
Good info from Rockford Fosgate
http://www.rockfordfosgate.com/scripts/rightnow.cfg/php.exe/enduser/std_adp.php?p_faqid=145
With all due respect, I disagree with pretty well every statement here. But I do agree with your right to believe it.
Here is a pretty fair article on caps. Iv'e fiddled with them in my sons cars (I too old for that type of volume).
http://www.caraudiohelp.com/newsletter/car_audio_capacitor_myth.htm
Switch mode power supplies and charging systems cannot respond fast enough to keep the voltage from sagging. If the headlights dim (fairly local to the source), then no wire size in the world will help. Switch Mode power supplies are not known for their fast transient response, linears respond faster. Old discrete amps used to have huge storage caps internal to them for this purpose.
Good info from Rockford Fosgate
http://www.rockfordfosgate.com/scripts/rightnow.cfg/php.exe/enduser/std_adp.php?p_faqid=145
With all due respect, I disagree with pretty well every statement here. But I do agree with your right to believe it.
Thats cool Papa, the reason I posted it was because I disagreed with everything you posted prior.
Respectfully JetStar
Respectfully JetStar
Maybe Rockfordfosgate switching state power supplies are slow to respond - they should know best. Older design Switching state power supplies switch at a much lower rate, which increases their response time. Switch speeds up at 1 MHZ are no longer uncommon.
The ones I work on respond fully in about 2 microseconds, the output is not affected at all by power sags of 25 percent or more - this is when running at the 1 KW (1,000 watts) level.
This is, of course the beauty of a switching state power supply. Near 100 percent efficiency with very rapid response. They are just as happy drawing 100 amps at 12 volts or 200 amps at 6 volts.
The ones I work on respond fully in about 2 microseconds, the output is not affected at all by power sags of 25 percent or more - this is when running at the 1 KW (1,000 watts) level.
This is, of course the beauty of a switching state power supply. Near 100 percent efficiency with very rapid response. They are just as happy drawing 100 amps at 12 volts or 200 amps at 6 volts.
Originally Posted By: Papa Bear
I have seen many power amps with a 1-10 volume control that was useless/dangerous after "7" because it was clipping. So, in reality, it only had a 1-7 volume control.
Until you use a quieter source.
Originally Posted By: Papa Bear
You could always run a heavy dedicated hot wire from the battery (fused of-course).
Is there an alternative?
I have seen many power amps with a 1-10 volume control that was useless/dangerous after "7" because it was clipping. So, in reality, it only had a 1-7 volume control.
Until you use a quieter source.
Originally Posted By: Papa Bear
You could always run a heavy dedicated hot wire from the battery (fused of-course).
Is there an alternative?
JHZR2
Staff member
Originally Posted By: cchase
People are thinking the caps are just for long-term energy storage... they're usually to absorb instantaneous demand on a subwoofer for individual bass.
That's right. There is more or less no "energy" stored in a regular capacitor. Even a supercap has very limited energy stored. This is why some people do actually add a second small battery, as then if there is need to go through a long transient, the device can keep up.
Figure the alternator is putting out at a constant rate, and the sound system calls for enough current to cause a voltage sag. The cap will only have the energy sufficient to keep things up for a few miliseconds to maybe a second. Beyond that, the cap is flat. So, then not only do you have to provide all power from the charging system, but it also needs to recharge the cap before it is useful. How well this all works depends upon parts sizing and I suppose how dynamic the music is.
People are thinking the caps are just for long-term energy storage... they're usually to absorb instantaneous demand on a subwoofer for individual bass.
That's right. There is more or less no "energy" stored in a regular capacitor. Even a supercap has very limited energy stored. This is why some people do actually add a second small battery, as then if there is need to go through a long transient, the device can keep up.
Figure the alternator is putting out at a constant rate, and the sound system calls for enough current to cause a voltage sag. The cap will only have the energy sufficient to keep things up for a few miliseconds to maybe a second. Beyond that, the cap is flat. So, then not only do you have to provide all power from the charging system, but it also needs to recharge the cap before it is useful. How well this all works depends upon parts sizing and I suppose how dynamic the music is.
Bingo, you have it! As all good electronic techs know, a 1 Farad capacitor will deliver 1 amp for 1 second while discharging 1 volt, by definition. Only 1 lousy amp!!! Now if you are emitting tacan pulses (Tactical Air Navaigation) 3 micro seconds long then you can can easily pull 100 amps for 3 micro seconds and only reduce its voltage by 3/,1000,000 X 100 or 300 microvolts of powerline sag. Perfect for high power pulses with very short duration. But, a bass amplifier driving a woofer that lasts for 1 second and dims the headlights???? Nope, back to the Delorean joke, you need a flux capacitor!!
An older post refers to "linear" power supplies. With huge inefficiency and resulting overheat and premature aging issues, these are just about gone from the market.
on a related note..... our new appliance energy efficiency standards have resulted in all of our "walworts" (power supply cubes that plug into your outlets) to become switching state designs. Wow, unlike the old warm or hot to the touch linear supplies, these stay stone cold!!!!
Many of our DOE/EPA regulations have resulted in real gains for consumers!!
on a related note..... our new appliance energy efficiency standards have resulted in all of our "walworts" (power supply cubes that plug into your outlets) to become switching state designs. Wow, unlike the old warm or hot to the touch linear supplies, these stay stone cold!!!!
Many of our DOE/EPA regulations have resulted in real gains for consumers!!
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