capacitor?

[beavis240]

so i have MMC6500's MMC690's and 2 MM12's in my honda accord. im gonna run the C400.4 for the speakers, and C300.2 for the subs. I know this is takin a lot from my battery so i wanted to know if i would need a capacitor? or two? i dont really know a lot of that kinda stuff. any suggestions on what to do or what brand capacitor is good?

[exalted512]

are your lights dimming?
-Cody

[neomagus00]

i don't think the stuff is installed yet... in any case, a cap can never hurt; amongst the name-brand people, look for low ESR (equivalent series resistance; it'll be mostly the same amongst caps) and get a round cap, not a square one. other than that, get whatever you think looks good. if you can, get an optima yellow-top battery, even if you have to forgo the cap to get it, this will help you more. sometimes a cap won't help light dimming, in which case you can simply put small capacitors in the headlight line - no more dimming :)

[TrappedUnder Ice]

ACK...NO cap is needed- Period

Dont be fooled into wasting your time or money on a cap

Next....:mad:

[exalted512]

figures....he doesnt post in a few months and when he does its about a cap...lol
-Cody

[MacLeod]

I agree with TUI. Ive seen to many kilowatt+ systems with stock alternators and an Optima battery and they all worked fine.

[LittleCar_w/12s]

hehe, I'm about to put a kilowatt into my little 80hp car.. we'll have to look at gas mileage changes before it's over... maybe I'll find a good GM truck altenator to squeze in there.... Other than that my yellowtop works just fine for most cases, and the 700w I used to run just barely dimmed the lights.
-Jerry

[neomagus00]

hmmm.... only reason i rec a cap is because of the strain it seems to put on a battery... now, i have absolutely no factual evidence, but it seems to me that pulling power then pushing it through the battery at a hundred times per second isn't so good for it, whereas if you use a cap, which is designed for exactly this, the battery only sees a load of on or off (i know this is simplified, but it gets the point across...) can this changing draw harm a battery? is there any harm in adding a cap?

[exalted512]

they have something called a "batcap" now...do a search for it in google...supposed to be really good
-Cody

[TrappedUnder Ice]

unfortuanatly....caps do not "relieve" the strain on the battery. If anything...the battery has something else to charge!

Cap= a/c filter

[neomagus00]

Cap= a/c filter
yes, so for the duration of the bass note, the cap deals with the ac aspect of the draw, and all the battery sees is a constant draw - the strain i referred to was the strain of an ac draw on the battery of at least 20 hertz... i don't know what this does to a battery, but it can't be good, even if it's not bad. a battery is, however, designed for varying dc loads (turning air conditioning, cooling fan, etc. on and off).

[TrappedUnder Ice]

Problem is...cap cant charge and re-charge quicke enough to keep up with most music.. so its kind of pointless.

Caps can be useful on mids in high end systems to help extend dynmaics...about it....other wise there are better options then caps

[neomagus00]

i'm not sure what you mean by 'charge and recharge quickly enough to keep up with most music', could you elaborate a bit? at the very least, if a cap can't keep up with a bassline, how's it gonna deal with midrange, a factor of 100 times faster (higher frequency)?

[exalted512]

Originally posted by neomagus00
i'm not sure what you mean by 'charge and recharge quickly enough to keep up with most music', could you elaborate a bit? at the very least, if a cap can't keep up with a bassline, how's it gonna deal with midrange, a factor of 100 times faster (higher frequency)?
because it doesnt draw as much power
-Cody

[Joelsbass]

exactly cody.... lower frequencies require more movement and thereby more power to reproduce, hence the fact that most lower end subs run around 300-400 watts whereas most component sets run 100-200 watts, higher end subs run from 600-1500 watts per sub... 1500 watts for one speaker vs 150 for 2...

[neomagus00]

yes, clearly bass requires more power, but the cap isn't intended to take the load off of the battery entirely, it is intended to buffer the ac draw from the battery. the current draw from the battey without a cap would be the absolute value of sin, or the position function of a perfect bouncing ball, or... um... a bouncing bunny (roughly, for all three, the small caps in the amp should mellow this out a bit)? so all the cap does is draw a constant current from the batter, presumably at .707 times the peak of the current draw from the amp (just the average), while allowing the amp to have it's way with the cap. if you have sufficient capacitance, with any pause between bass notes (even with an overdraw from the cap), you'll see a full recharge. is that written clearly?

[LittleCar_w/12s]

not only that, but you have to keep in mind the additional benefit of the cap over the battery. the battery shows a resistance to the line of current, mainly because it's cells actually ahve to react internally to produce the power. this is why it has a detrimental effect on AC draw. A cap copmes in handy, because the super-fast discharge rate makes it show a superbley low circuit impedance. THIS INCREASES YOUR PERFORMANCE!!! this is why it helps.

Now, there are two types of capacitors, one is electrolytic, and the other is di-electric only. the electrolytic is higher capacity but has a slower rate of discharge. this is why caps arent the solution to every power draw buffering problem, but they help. A strictly di-electric capacitor hold's very little energy, but is capable of speeds of discharge equivalent to how fast the electricity can travel down the wire!

The (electrolytic) capacitor's electrolyte layer is usually under one hundredth of an inch thich... let's compare this to the 1/4" between plates in a car battery...... now do we see why a car battery holds more, but has a higher impedance?

You CANNOT have a capacitor FOR your battery, as it would be the size of your entire car. However, you CANNOT expect a battery to behave as fast as a capacitor. The combination of the two allow us a much better power supply. In fact if you had enough money and you cared enough, a bank of the battery, a good electrolytic capacitor, and a large di-elecrtic capacitor would even out your supply to it's maximum. However the internal workings of your audio equipment will take care of any need for the latter type of capacitor.

Please, if you want a capacitor, go for it. It is neither a waste in time or money.
-Jerry

[bknauss]

Originally posted by exalted512
they have something called a "batcap" now...do a search for it in google...supposed to be really good
-Cody

Lots of marketing. Marketing is the tool of the devil... also known as B*se.

[exalted512]

Originally posted by bknauss
Lots of marketing. Marketing is the tool of the devil... also known as B*se.
so youre saying its not worth it?
ive heard a few ppl that have a pretty big knowledge of car audio endorse it...
endorse as in say its good...theyre not getting anything out of it
but its pretty new, so i guess time will tell
-Cody

[bknauss]

Having a big knowledge of car audio and having knowledge of electricity can be two completely different things at times.

That's my 2 cents.

[exalted512]

this is true, but what do you think about the batcap?
-Cody

[AustinKP]

Originally posted by exalted512
this is true, but what do you think about the batcap?
-Cody "Lots of marketing. Marketing is the tool of the devil..." ...I don't think he likes it...

[neomagus00]

it seems like a good idea, but i would prefer a standard optima/cap setup for two reasons - one, the standard is proven, which is why it's standard, and the batcap is new and unproven; two, the bright battery and shiny silver cap look way cooler than the dull white or black of the batcap :p. it seems to be doing well in spl comps, or so the site says, but time shall tell.

p.s. bknauss - in what way is a fundamental knowledge of electricity and electronics different in home and car applications?

[exalted512]

Originally posted by neomagus00
p.s. bknauss - in what way is a fundamental knowledge of electricity and electronics different in home and car applications?
theres not a difference, you just use different numbers...such as 120v compared to 12v
-Cody

[neomagus00]

well, there's clearly differences, such as that 120 volts being ac and the 12 being dc, but fundamentally, once you realize things like that, is there a difference?

[exalted512]

no
electricity doesnt change just because the numbers do...
the biggest difference is voltage since a lot of the internals of amplifiers is different
-Cody

[neomagus00]

no, i know that the electricity doesn't change, that was the response i was trying to get from bknauss :). the point i was making with the ac vs. dc was that you can't use them in exactly the same way... you try to put 12 volts ac into a car amp and you are either going to have a dead amp or some very trippy music.

[LittleCar_w/12s]

Home VS Car... Not a bit of difference...
The home equipment has less disadvantages to BUILD, but using it is the same. Most of the Extras we add to car audio are not needed in home because of the power source, and home can use all the space they want. The electricity remains the same, however, less the fact that at lower voltages more energy is wasted as heat than higher voltages.

As for the BattCap??
The batcapp is only a new model of an old thing. simply a different electrolyte that has more joule-holding power. You're right about the 'proven methods' though (NEO), we may see this new electrolyte eating through the casing in a few years, who knows. I will however say that you can get a 1 Farad cap the size of a cm-thick penny. It only handles about 1.5 volts and will run you a high dollar (you could build one for your car out of 10 of them in series for 15v, but do you have over $700 to blow?).

There are lots of better caps out there, we just don't feel like affording the room for the cheap ones, or the money for the small ones. So go with what the market has found the most affordable and reliable.
-Jerry

[bknauss]

wait a dog gone minute. The electrical systems of a house and a car are COMPLETELY different.

A house is fairly simple... 120V +/- 10% at 60Hz. Unless you're in CA or about to have a blackout, you'll hardly ever see it really swing to that +/-10%, even with heavy current use. If you use too much current, the breakers switch off and you're without electricity until you switch it back.

The car is different. The battery is generally 12V, your alternator charges at 14.4V, and as we all know, the alternator can't always stick up at 14.4V. This is due to the battery needing to output more current that the alt can't provide, so it sags, and generally you never get up to 14.4V, and if you do, its for short periods. Then you start throwing in that the alternator provides different current at different RPMs, it makes it a fairly unpredictable system if you're playing music. I drove around one day with a meter on an amp and looked at the voltage (this was with a C300.2 and a 1kW amp). When I was playing bass heavy music loud, the voltage was hanging around 12.5 to a little over 13 for most of the time. There were a couple times I dipped below 11V. When I had the music low, it would stay more stable around the mid 13s. If we say 14.4V is what the voltage is supposed to stay at, and say 12V is the greatest amount of change, we're talking about a 20% swing in voltage... much more than the 10% you'll barely ever see in a house.

[LittleCar_w/12s]

BK, I was explaining the use of electricity is the same in both, in response to your post of BKnauss: Having a big knowledge of car audio and having knowledge of electricity can be two completely different things at times.Basically I guess I took that to mean you were saying that car audio does not apply to the same electrical principals as home or even other electrical applications. The electric motor in your food-chopper lives by the same laws as that amp in the back of your car. That's all I was saying. I even mentioned the considerable difference in power supplies, and that the ONLY major difference is the increased loss of usefull power due to high-current (needed with lower voltages) heat dissipation.

But, thanks to Anal Correction Man we now know the difference in power supplies. Also know that your vehichle's battery can drop to below 6 volts when cranking... fun, fun!
edit:/\ How's that for a percentage of swing, eh,? (58.3%)

-Jerry

[exalted512]

the question was: in what way is a fundamental knowledge of electricity and electronics different in home and car applications?
to me thats a no...the fundamentals of electricity is the same whether the voltage varies or not
thats what me adn jerry were talking about
-Cody

[bknauss]

I was commenting that having a vast knowledge of electrical engineering stuff does not mean you'll have real world knowledge of electrical systems and how they work, or be able to apply that knowledge in a good way. You can be a 4.0 student coming out of Cal Berkley with your BSEE, but there's a huge gap to bridge before you'll be a productive member of a company. There's simply too many things that you don't/can't go over in a class room. Most things learned in a class room or a lab are fairly theoretical. Until you are forced to go out and create even a somewhat complex system, you won't grasp how little you know.

In the case of capacitors, its a great idea... in theory. But when you don't think of things like ESR, you add in a charge up time for the cap and also that extra strain on the charging system. Or that certain types (materials) of caps are better at certain applications than others. Ceramic caps are great at filtering out high frequencies in switching power supplies, but electrolytics are pretty terrible and can make or break if the power supply works. I was spending hours in the lab at college with a built power supply not working for that simple reason. WTF, right?

Yup, that made no sense... an afternoon full of meetings has killed my brain.

[MacLeod]

Originally posted by bknauss
I was commenting that having a vast knowledge of electrical engineering stuff does not mean you'll have real world knowledge of electrical systems and how they work, or be able to apply that knowledge in a good way. You can be a 4.0 student coming out of Cal Berkley with your BSEE, but there's a huge gap to bridge before you'll be a productive member of a company. There's simply too many things that you don't/can't go over in a class room. Most things learned in a class room or a lab are fairly theoretical. Until you are forced to go out and create even a somewhat complex system, you won't grasp how little you know.


Im gonna stick up for Brian here. I agree 100% with this. Take truck driving school. I went for 8 weeks, 8 hours a day, 5 days a week. Driving and backing, shifting and backing. Youd think I was ready for the road. Well when I first got out there on my own in that 80,000 pound, 75' long monster it was a whole other story. It took me months before I was comfortable behind the wheel.

Now I know truck driving school is freaking childs play compared to Engineering school but its always the same. Cops I know tell me the same way. 16 weeks in the academy and 12 weeks ride along and when they first get out on their own they feel like a kid.

College only prepares you to discover how much you DONT know.

[bknauss]

macleod brings up an excellent point... its not simply engineering stuff like I was talking about, its about a ton of stuff out there. Macleod gave us the truck driving example, my girlfriend is doing something completely different from what she studied in college, etc etc.

As I've heard many times before, college is simply a process to weed out the people who can't learn well.

[exalted512]

i cant learn worth a shit
i just failed another chem test
im not sure what im going to do next semester...i might be going to a tech school or something
the sad part is i dont even what im doing wrong...i study, hell, i pay to go study in tutorials...
AHHHH
-Cody

[LittleCar_w/12s]

well you have to remove the woofers from your ears if ya want to hear anything Cody...
I'm a bit of a slacker right now. I've spent the last two years wasting my time, of course life didn't help out much, and Uncle Sam woouldn't lend me more than $6G, that bought me 1 semester at a 4yr college... The rest of what I've done is out of pocket at Com.College.
It really hurt having to cancel an entire semester of classes a year and a half ago (stolen money from bank acct, I had to work 3 jobs to pay rent...) Of course no money back from the college...

So don't feel bad Cody That cut my gpa in college in half... and emptied my wallet too. It's just life doin a number on ya, just gotta keep goin until you can't afford it.