Choices of speakers

[Tomcio]

Actually there is a simple answer, and that answer is no.

I wouldn't be so quick with a simple "no" answer here.
Please note that I mentioned "noise" in the electrical system. For that the capacitor works as a filter and reduces noise. If your electrical and ignition systems (as I mentioned) are not in good working order you might have some alternator "whine" or ignition spikes. If the amp doesn't have good filters built in you will hear that noise over the speakers. In those cases a capacitor will definitely work and will help filter out the noise.

[Malevy]

For some reason, I am subscribed to this thread??

But, anyway- IMHO, that capacitor article is misleading and their conclusions are wrong.. Capacitors are in parallel with the power to the amplifier, so any internal resistance of capacitor is irrelevant. There is no way it "takes" power from the amplifier. The purpose of the capacitor is to maintain the voltage when the current demand of the amplifier spikes beyond the capabilities of the car's electrical system. For that instant of time when the bass hits, a fraction of a second later when the power demand drops, the capacitor recharges with the excess being supplied from the alternator. It is a long standing audiophile modification to any amplifier to add capacitors to the power supply in order to increase "headroom", reducing distortion when the limits of the power supply are reached. In a car amplifier, it would be more effective to add the capacitors internally after the DC to DC power supply, but most people are not about to crack the case open and solder in extra capacitors (assuming there is space for them, typically not in a car amplifier).

The ideal situation would be to have enough power available such that the limits are never reached (eliminating the need for the capacitors), but when building a high power system in a car we have the limits of the car's electrical system to deal with.

I had to add a capacitor in my DMC because when the bass was pumping, the ECU would cause the AFR to go way lean. The voltage fluctuating messed with the reference voltage on the sensors (I am running a VQ engine, not PRV). It made a big difference, but I also had to add some thicker wires for various electrical grounds on the car, and the wire from the alternator to the battery had to be upgraded.

Noise is usually from open grounds, or ground loops. It is rare that a "noise filter" (or capacitor) on the power supply line will fix various electrical noises (most common is alternator wine). Some filters that use coils (or, "chokes") are helpful at reducing noise from the ignition system.. But modern resistor plugs and ignition wires have made that problem less common.

[rdarlington]

I don't see anything wrong with the article. Nothing that doesn't jive with all those EE courses I took anyway. I actually design amplifiers and got into an argument with those audiophools that think they know anything about audio engineering. You know, the guys willing to drop $2500 on a power cord because that OFHC copper wire somehow filters out line noise from the 37 miles of copper on the other side of their outlet. My background is in designing ultrasound amplifiers for the local national laboratory here in Los Alamos for the materials research guys. This requires distortion in only vertical amplitude and anything else is undesirable. I'm told that this kind of amplification makes music sound bad. I argue that it's the original recording that sounds bad because all I'm doing is making it louder. I do a lot more than that , but that's just one specialty. For shits and grins, I built a few audio amps. Silicon and tube based to round out my experience a bit. Tubes add distortion that does sound pleasing to the ear. I studied the psychology of the audiophool. I measured the high end speaker cables and compared to the same measurements done on coat hangers (using my Agilent 8712ES vector network analyzer). I've tried to do blind studies but they all refuse. They know their ears can't possibly hear a difference.

So, to address the cap mod and everything else above, it's in their head.

-Bob

For some reason, I am subscribed to this thread??

But, anyway- IMHO, that capacitor article is misleading and their conclusions are wrong.. Capacitors are in parallel with the power to the amplifier, so any internal resistance of capacitor is irrelevant. There is no way it "takes" power from the amplifier. The purpose of the capacitor is to maintain the voltage when the current demand of the amplifier spikes beyond the capabilities of the car's electrical system. For that instant of time when the bass hits, a fraction of a second later when the power demand drops, the capacitor recharges with the excess being supplied from the alternator. It is a long standing audiophile modification to any amplifier to add capacitors to the power supply in order to increase "headroom", reducing distortion when the limits of the power supply are reached. In a car amplifier, it would be more effective to add the capacitors internally after the DC to DC power supply, but most people are not about to crack the case open and solder in extra capacitors (assuming there is space for them, typically not in a car amplifier).

The ideal situation would be to have enough power available such that the limits are never reached (eliminating the need for the capacitors), but when building a high power system in a car we have the limits of the car's electrical system to deal with.

I had to add a capacitor in my DMC because when the bass was pumping, the ECU would cause the AFR to go way lean. The voltage fluctuating messed with the reference voltage on the sensors (I am running a VQ engine, not PRV). It made a big difference, but I also had to add some thicker wires for various electrical grounds on the car, and the wire from the alternator to the battery had to be upgraded.

Noise is usually from open grounds, or ground loops. It is rare that a "noise filter" (or capacitor) on the power supply line will fix various electrical noises (most common is alternator wine). Some filters that use coils (or, "chokes") are helpful at reducing noise from the ignition system.. But modern resistor plugs and ignition wires have made that problem less common.

[Malevy]

Starting my career at Bell Labs, with lots of experience in analog, digital, and RF design.. I respectfully disagree.

If the input voltage to the amplifier drops, the power output will too-- and if it is being pushed to it's limits, it will distort. A better power supply will eliminate the need for the capacitors, but will be a lot more expensive.

[dmruschell]

For some reason, I am subscribed to this thread??

But, anyway- IMHO, that capacitor article is misleading and their conclusions are wrong.. Capacitors are in parallel with the power to the amplifier, so any internal resistance of capacitor is irrelevant. There is no way it "takes" power from the amplifier. The purpose of the capacitor is to maintain the voltage when the current demand of the amplifier spikes beyond the capabilities of the car's electrical system. For that instant of time when the bass hits, a fraction of a second later when the power demand drops, the capacitor recharges with the excess being supplied from the alternator. It is a long standing audiophile modification to any amplifier to add capacitors to the power supply in order to increase "headroom", reducing distortion when the limits of the power supply are reached. In a car amplifier, it would be more effective to add the capacitors internally after the DC to DC power supply, but most people are not about to crack the case open and solder in extra capacitors (assuming there is space for them, typically not in a car amplifier).

The ideal situation would be to have enough power available such that the limits are never reached (eliminating the need for the capacitors), but when building a high power system in a car we have the limits of the car's electrical system to deal with.

I had to add a capacitor in my DMC because when the bass was pumping, the ECU would cause the AFR to go way lean. The voltage fluctuating messed with the reference voltage on the sensors (I am running a VQ engine, not PRV). It made a big difference, but I also had to add some thicker wires for various electrical grounds on the car, and the wire from the alternator to the battery had to be upgraded.

Noise is usually from open grounds, or ground loops. It is rare that a "noise filter" (or capacitor) on the power supply line will fix various electrical noises (most common is alternator wine). Some filters that use coils (or, "chokes") are helpful at reducing noise from the ignition system.. But modern resistor plugs and ignition wires have made that problem less common.

^What he said. A kick drum sound takes a lot more electricity to produce than the rest of the music. But, the kick drum isn't produced constantly (unless you're a metal head like me lol). If the electrical system can keep up with the average demand of the sound system, but the voltage sees a momentary dip when a kick drum (or similar sound) is produced, a capacitor will supply the needed momentary electricity needed to keep the audio from distorting and the car from malfunctioning. Because the car's electrical system can keep up with the average demand, it can recharge the capacitor for the next time it's needed.

[rdarlington]

That is not true. That's not at all what capacitors do. You will be limited to the voltage supplied by the power supply, and in this case the limiting factor will be the battery & alternator combo.

[rdarlington]

12 years here at Los Alamos National Lab doing much the same thing, including pulsed megawatt RF sources for accelerators and the like (among other things).

-Bob

Starting my career at Bell Labs, with lots of experience in analog, digital, and RF design.. I respectfully disagree.

If the input voltage to the amplifier drops, the power output will too-- and if it is being pushed to it's limits, it will distort. A better power supply will eliminate the need for the capacitors, but will be a lot more expensive.

[DMCMW Dave]

^What he said. A kick drum sound takes a lot more electricity to produce than the rest of the music. But, the kick drum isn't produced constantly (unless you're a metal head like me lol). If the electrical system can keep up with the average demand of the sound system, but the voltage sees a momentary dip when a kick drum (or similar sound) is produced, a capacitor will supply the needed momentary electricity needed to keep the audio from distorting and the car from malfunctioning. Because the car's electrical system can keep up with the average demand, it can recharge the capacitor for the next time it's needed.

Explain why putting a tiny battery (the capacitor) in parallel with a big battery (the car battery) without a resistor in between them has any impact at all.

[dmruschell]

According to Crutchfield (http://www.crutchfield.com/S-DZJ5cmp...itors/faq.html), the resistor is only used for initially charging the capacitor and is then removed. Now I'm going to let the experts sort this one out.

[Bitsyncmaster]

According to Crutchfield (http://www.crutchfield.com/S-DZJ5cmp...itors/faq.html), the resistor is only used for initially charging the capacitor and is then removed. Now I'm going to let the experts sort this one out.

This is an old trick to bring an old (sitting on the shelf a long time) electrolytic capacitor back to life. It "forms" the layers of foil and insulation back to normal. We use to do it attaching a variable power supply and slowly cranking up the voltage over a few hours to the capacitors rated voltage. A resistor would do the same but less controlled.

The usefulness of adding a capacitor depends on the capacitors resistance (best is very low) and the resistance of the wiring from the capacitor going back to the battery. So poor wiring in the car would make the capacitor do more as designed. But what I see with these big amps is #6 AWG wire running right to the battery. In that case, the capacitor will do nothing to help.