I was in best buy this weekend just killing time. Looked at capacitors and the salesman came up and started talking to me. I have an audiobahn 300 watt amp. When I start up my truck i usually get 14.7 volts. When I play a song with alot of bass it will go down to about 14 volts. Some mornings I get like 14.3 volts and with alot of bass it goes down to 13.7. Anyway I was wondering if a capacitor would do me any good. The guy at best buy said "it was good practice to run a capacitor." I always thought they were like a second battery. I was thinking of getting an audiobahn cap to match my audiobahn amp. Any input would be appreciated.

 

You can get it but it really won't change anything about how your electrical system is performing. It appears like you have no problem at all. A cap only helps to smooth out VERY SMALL voltage drops.. it won't increase your system voltage AT ALL. It will only help to maintain a constant voltage when your amp hits a hard bass note.

The cap will only charge up to whatever your system voltage is.. whether it be 14.4 or 13.7 or whatever.. it won't go any higher than that. When a hard bass note hits.. the cap will discharge as the battery/alternator are not "fast" enough to maintain a smooth system voltage during peak demands. Keep in mind that that cap discharges VERY QUICKLY and won't support extended power dips.

Although, it is a BIG debate whether a Cap does anything at all. If a Cap does help with power supply to the amp.. its a VERY VERY small amount.

 

I might just have to get me one.... Thanks TEk2000

 

No problem man... oh and the Audiobahn cap won't perform any better or worse than an off brand Cap.
All of those brand name manufacturers just slap their name on a Cap that's produced by another company and mark it up an ungodly amount.

So, its more for show than anything.

 

TEK2000 and everyone else who might be curious:

A good friend of mine is an electrical engineering kind of guy and was wondering the exact same thing: Are the caps hype or not?

He made a fairly elaborate test bed and ran some tests. You can read all about it here:

Real World Stiffening Capacitor Test

You might be surprised at what the data says...

 

Thanks for that article B-Man... its good to see some solid evidence from a controlled test.

So, my position was actually pretty accurate... it helps but a VERY VERY little bit. 1 dB increase is audible but that's the smallest amount of change the average human ear can percieve.

I've heard some people mention that the Cap would be most effective if installed on the rail voltage of the amplification stage. This will help prevent power dips directly during amplification rather than trying to maintain power supply consistency.

Ultimately, it doesn't appear that a $100 or so investment for a Cap is worth it considering that his test results yielded an increase that is probably not even audible.

I see he stated using a Linear brand amp.. from the picture I think he was in fact using a Linear Power amp... GREAT AMP!!!

 

I will probably still get a cap, but this is dissapointing on what little bit of gain you get. I thought there was more to them than that. Thinks for all the info Tek2000 and BMan.

 

What about the electical system? Does it help take any kind of load off? Or do you still need to get a batterey to help? I have a freind who was runnin alot of power and when he stopped his headlight would dim under big pulls of power. Would a cap help any with that? I plan on running quite abit of power and want to have every thing set so i dont have to keep adding stuff to make it right.

Thanks,
X

 

I think you would definitely want to look elsewhere than a Cap... perhaps a batcap ( www.batcap.com ) or a high output alternator.
To my understanding, extra batteries are primarily used for competitions or other times when you're playing the stereo without the vehicle running.

It sounds like your friend needs more current than what his alternator can provide while idling.

 

Actually, a cap ADDS load to your electrical system. A large cap appears as a direct short to the electrical supply, until it charges up.

The only time you will see a cap improve anything so it is measureable is if you are suffering from inadequate supply power at the amplifier. It will help for EXTREMELY SHORT duration bass strikes, like a drum roll for example.

Of course, the right way to cure that would be to skip the $100 cap and buy power cables of the proper size for the load you intend to operate them under.

 

A cap should be OPEN not a SHORT. If it were a short it would never charge up.. you'd be connecting the + side of the battery direct to the - side of the battery.

 

I didn't say it WAS shorted, I said it APPEARS as a short to the electrical supply, until the cap charges up anyway.

A cap (when discharged) appears as a short to an electrical supply. As it charges, the amount of current flow reduces and the voltage across it increases until it is equal with the source supply.

 

I'm not understanding your claim that it APPEARS as a short to the electrical system.

A capacitor is simply 2 conductor plates with an insulating material between the 2 of them. This is an OPEN to DC since DC does not pass through a capacitor. The Cap is wired in parallel to the amplifier connected directly from - to +. If the cap were wired in series the amp would never recieve power and would not turn on. If the Cap "appeared" to be a short.... 1) it would never charge because the electrons would flow directly through it. 2) it would blow the fuse or create a serious battery problem because you've got direct current flow from - to +.

 

TEK2000 -

Until a cap charges up, it is basically a short to an electrical supply. If you don't believe me, try this:

1. Get the biggest 12VDC capacitor you can find.

2. Get a 9VDC battery.

3. Connect the negative lead of the battery to the negative lead of the cap.

4. Wire a meter in series with the positive lead and set it to the highest amperage scale on the meter.

5. If you have a voltage meter available, place it across the battery terminals so it reads 9VDC.

6. Connect the positive meter lead to the cap, completing the electrical circuit.

You should observe 3 things:

1. The voltage meter will drop to almost 0VDC, if the cap is big enough. This is exactly the behavior of a "short" on an electrical supply.

2. The amperage meter will slam over to the rated output current of the 9VDC battery.

3. Now, as the cap charges, the amperage will steadily decrease and the voltage will steadily increase, unitl you read about 9VDC on the volt meter and virtually 0 amps on the current meter. (Actually, there will be a slight amount of current flowing due to imperfections in the cap, but your meter may not be sensitive enough to read it).

Discharge the cap by shorting across it's terminals, reconnect the battery and watch it again if you don't believe me.

Of course, if the cap is a farad (like the one being discussed in this thread), the 9VDC battery will probaly exhaust itself trying to charge it and you will never see the voltage go back up.

 

Alright B-Man.