It is true that stiffening capacitors act like batteries but in a very different way. They can be charged and discharged at a very high rate. Think of it like this. A car battery is like a garden hose, It can only flow so much water at a time. A capacitor is like a bucket of water, you dump it out and it all comes out at the same time. Think of it as being a 10 inch wide hose instead of an 1 inch.

So what happens, is when the amplifier needs extra current to cover a transient in the music the capacitor is a quick source of energy. A car battery contains a much larger amount of stored energy, but it can't deliver it at a fast enough rate, because the pipe is to small.

If an amp requires more energy than there is available it will begin to distort the music because it can't produce enough current to push the speaker to produce the right sound. This is where a large capacitor(as opposed to the smaller ones inside an amp) can help maintain the power needed. This usually happens with bass notes because sub speakers require more current, because they must move a larger volume of air than higher frequency speakers.

One thing that can remedy this is to use a larger sub, because they can move more air per a given bass note. Therefore, in theory(depends on how the speaker is designed - high power or low power), they require less energy than a smaller speaker to produce the same amount of sound.

On the subject of multiple batteries-- This is never a good idea, unless you want to listen when the car is off. A car battery is the biggest load on an alternator. When you add a second battery it loads the alternator even more and you will surely see lights dimming when this happens. The voltage will drop right down to what the batteries can supply, approximately 12V instead of the 14.4V normally.

Also, this extra load on the alternator means more current flow throughout the system which usually means serious alternator whine in the sound system. There is nothing worse than that. You will be much happier with one battery, trust me.

 

NOt to get off topic, but where is the most common place to mount the yellow top OPtima battery. I have been contemplating installing one since my power need for my audio/video is growing.

In the engine bay, in the trunk?

doc

 

Totally dont agree with that. I agree its more load on the alternator, but you definately will NOT see lights dimming because the power is increased by using more batteries. I myself have 2 extra batteries in the trunk, and there is no light dimming at all nor is there any alternator whine. Adding batteries was the perfect solution for current sucking amps. I have 200amp and a 120amp amplifiers, which is way more then the stock alternator can handle. Stock alternator is only 100 or 120amps? not sure. Those are peak currents but none the less very large numbers. I dont know the details of why it works, but from personal experience IT WORKS. Adding batteries was the best thing I could do to stabilize my system. Thats just my personal experience and my .02 cents


As for where to place the extra battery, i would say you have to go in the trunk closer to your amps, and more room, it might be hard to stick it in the engine bay, i dont even know where you could put it.

 

I'm not saying that your lights will dim if you use to batteries, it's just more likely, because it increases the load. But, If the batteries are not being drained, because the alternator is handling the load, they won't need to charge, therefor no load. By the way, those two amps would probably not be all that big a load anyhow. Those kind of problems start happening up around 500 watts. A good way to tell what they will draw at max is check the fuses. If you have say a 40 amp fuse and a 30 amp fuse, they will draw a maximum of 70 amps. 70amps x 12volts = 840 watts. This would only happen at maximum, which never happens continuously. This is where a stiffening cap can help. By the way, only about half of those watts actually makes it to the speakers, do to efficiency loses. Anyway, the second battery will only help when the car is off. If you can isolate one of the batteries and disconnect the other while driving, you will do much better and take some of the load off your alternator, and it will last longer. Dave Novone wrote an article about this along time ago when the extra battery was becoming popular. He was a co-author of the Autosound 2000 tech briefs. Good stuff. Have fun!!!

 

Umm i said 200amps not 200 watts, my sub amp is 1800watts rms and 2000 watts peak (that is most likely under rated anyways). and my 4 channel is another 800x4 watts about 100amps or around there. so yea its not a small load. i understand that it doesnt use the full load all the time but i was just saying it is not bad for you and that it works. I would say extra batteries usually always help. Yes its bad if you are putting the max power output continously but as you said that always doesnt happen. I also have a 35Farad Batcap in my car. As far as disconnecting the batteries, i usually listen to it pretty loud and if i didnt need it, i wouldve never put it in there. well its mainly just to be on the safe side, because in my last car with this amp, ive blown it twice due to not enough power, lower volatage, dont want that to happen any more.
also the amps are more then 50% efficeint, or else youve got something like the sony xplods? haha i dunno but i know its more then 50%.
thats just my opinion not trying to say your wrong or anything but do appreciate your idea of battery isolation and might look more in to it.

 

Wow!!!!! I thought you meant watts. That much power is unreal. It must kick so hard the windows shake, maybe even break. In that case you definitely need more batteries, but you need the cap for sure, because I don't care how many batteries you have, you wouldn't be able to get the power there fast enough. I've never used more than 800 clean watts in any car, so I wouldn't have a clue what that must sound like. The 50% figure is sort of a guess. Actually the better quality amps(class A) are usually less effecient, but higher quality. But your right the typical amps out on the market are usually class b/c which sometimes reach 70% efficiency. You also have to factor in the loss from the wires and the voice coils in the speakers, but with your system, who cares, let her rip!

 

This was a perfect thread for me since I was in the market for a cap this past week... My buddy and I were discussing everything we've heard about caps, and we decided we wanted to know once and for all (just for our own knowledge) what it would and would not do for us... We are running similar systems... I'm running the stock head-unit, an MTX 564 for my mids and highs and an MTX 421d for the bass... When the bass would hit (Car at an idle), my fogs, markers, and licence plate lights would all dim very noticibly... Headlights, not really, and tail lights weren't really noticible...

I purchased a 1 farad Lightning Audio Cap with a digital readout... The results are as follows:

First and foremost, dimming has been reduced to almost none... So I would say for this it helped tremendously in my case...

Sound quality... No difference at all... I've heard it helps, I've heard it hurts... In my case, I notice none of the above...

What I observe... The display shows - (Engine off) 12.79-12.80, (at idle) 14.50-14.51... When the bass hits for a long time (techmaster) the lowest I've seen it drop to is 13.26, but it jumps right back up to the 14's the instant the bass stops... Even if it's between a series of deep bass hits, the time between is enough to get it back up to the 14's...

The conclusion I have come to on the subject of Capacitors is, there is no drawback of running one other than the cost... The only benefit I've seen is the reduction of dimming... This is not to agree or disagree with anyone, but I'm just simply sharing what the results are for my set up... I'm very pleased with the results and I will continue to run it... I was prepared when I purchased it to install it and then pull it out and trash it, all because I just wanted to satisfy my curiosity... Also, I want to add, I was very skeptical of both the pros and cons of running a cap, so I really didn't expect much... Maybe a little of both sides...

FWIW... Your Mileage May Vary...

 

I agree with your assessment. That is about what you would get. The difference in sound quality would only show up during transients and is difficult to hear if you don't know what to listen for. I had a demo of this years ago and they had to tell me what it sounded like, and it was definitely there. Unfortunately, I don't remember what that sound was, but I always run a cap now. Generally you get tighter bass response. If you are using quality amps, you will rarely have this happen. It's more of a preventive thing, kinda like running out of gas. As long as their is plenty of gas in the tank, no problem, but every once in a while you run out.

Good Luck!

 

has anyone tried a "batcap" ...which is essentially like a combination of the two. it will provide all the juice needed for extended bass, and recharges quicker than a battery.