enigma32

A) The battery supplies the power for the amp. If the battery is drained because of too much current draw for too long without a large enough alternator to charge it in the process, your car dies.

B) The wattage rating of the speaker doesn't matter when you're asking if your alternator will handle the load-- only the wattage of the amp. And if possible you should find the wattage that the amp *draws*, as you can then find out precisely how much amperage you'll be drawing.

C) Be careful with a speaker rated for more than your amp. You may think you won't blow it out, but it's easy to turn it up all the way and clip the amp-- then your speaker dies and you're screwed.

D) The capacitor is only for momentary draws-- that is, when your system "hits" hard. It won't help you in the long run if you're drawing too much power for for electrical setup.

HTH,
~enigma32~

Sk8r_dude

i didn't

V8kilr

Drop me a p.m. and I'll give you a hand,

MECP certified
1 IASCA award
3 SPL/DB Drag awards


2 SPL/DB drag awards where won in a 2nd gen rx7, the other in a 1st gen.



Heres a couple quick notes,
1- That 500w MTX amp will put out about as much as a 1200+ watt pyramid, so take that into consideration when calculating amperage draw.

2- Better name brand amps feature Bigger internal capacitors and more effecient power supplies to help reduce the amperage draw spikes.

3- Unfortunatly MTX and RF amps are built using new techonology then most amps, the run a totally different internal power supply that actually is extremely effecient is reducing heat but it creates amperage spikes like hell.

4- Make sure you run the proper wire size to the amp, if you find yourself on the boarder line then step up a gauge, I would recomend 4agu.

5- Your battery supplies 100% of your power YES 100%.

6- The alternator is only to keep the battery at 100%, If your alternator cannot keep your batter at 100% it will slowly but surely fall to 20% or less, at this time you will be drawing 100% of your power from your alternator THIS IS BAD AND THIS IS HOW YOU KILL AND ALTERNATOR.

7- Who ever said your battery puts out something like 5 amps IS ON CRACK, the amperage rating is clearly stated on the battery, USALLY IN BIG *** NUMBERS AND LETTERS.

8- A battery is rated in 2 ways CCA (Cold Cranking Amps) and CA (Cranking Amps) , To use my battery for example my CCA is 800Amps, and my CA is 1000 amps, CCA and CA are the amount of amps a battery can produce over a set amount of time. This figure is more then 5 amps

9- Competition systems such as the Boss Ford armored truck dont even use alternators, hell it dont even have an engine, my point make sure your battery is up to par as well as your alternator.

10- Capacitors are simply designed to throw out stored power in an insanely short amount fo time ( something your battery can not do) This is not something you pick up because your battery and alternator are not good enough, its something you buy because its a great add-on to any stereo system thats draw more amperage in bursts then what the battery, wire, and alternator are rated for. BUT if your system is constantly drawing more then your batt,alt, and wire are rated for your capacitor wont do anything for you.

85rotarypower

So why the hell can't the battery in my car keep up with the amperage draw without the car running while it can with the car running smart ***? If you answer that in a half belivable manner then I might consider it. The battery can supply that power for a short amount of time. It can't produce 800 amps of power constantly. If the battery is used long enough, that amperage the battery can put out is reduced and need to be recouperated. Like I said, one way around this is using a larger battery.

enigma32

85rotarypower, you're an idiot.

On a lighter note:

Think of a swimming pool full of water.
That's your battery.

You hook a pump up that takes the water out. That's your amp.

You dump a garden hose into the pool and turn it on. That's your alternator.


If you run the pump without the garden hose (the amp without the alternator) you suck it dry and the pool (battery) becomes empty.

But with the garden hose (alternator) running it replenishes the supply so you can run for longer.
This is also why if you draw (the amp) is greater than the source (the alternator) your supply will run out.

fatboy7

I question this statement, but I'm sure that to an extent you are correct. This is my arument:

1. A fully charged battery with no load on it whatsoever creates a potential voltage of 12.8V. When placed in a car with the engine running the voltage increases to 14.4V.

2. This means that an excess 1.6V is created around the alt-battery loop. This excess voltage creates a current going into the battery, not out of it.

3. If the battery has a net current going out of it, it is discarging. Thus the alternator is there to make sure that the current is always flowing into the battery.

That being said, I do also agree that the battery is the most important part of the power delivery system, in a high powered audio system. Music is a random process: the instananeous peak power required to create a musical 'note' is never known by the amp. The only reason you need high power amplifiers is the worst case senario where the phase of all the various frequencies being produced line-up and the signal level climbs to abnormal levels. If the amp can't keep up for these short bursts, it clips and distorts. Well, that and for dB/Drag events where its all about making your ears burst. Under normal listening conditions I'd be suprised if anybody actually uses more than 500 W rms. Peak power on the other hand can reach astronomical levels so far as the amps can put out.

Anyway enough of my ramblings. Just want to say that on average the alternator has to be creating all the power, most of the time, or the battery will eventally discarge. The alternator isn't very fast reacting however, and unable to produce very high levels of current. So just when the amps need the power the most, the alternator starts to crap out, the battery kicks in (the lights dim, etc.). That is the only time the battery is providing the power.

85rotarypower

Sorry guys, I was thinking stupid because I was all pissed at another thread about auto insurance. I hope to hell you are right though. Because that would explain the problems I am having right now.

I'm so stupid sometimes!!!

WanKeL FD RX-7

iTrader: (7)

hey 85rotarypower, will you be at the Ottawa meet this year?

85rotarypower

Wish I could. I'm having too many problems with my car. My electrical system seems totally screwed right now. The car runs and all, but I can't get the head unit to work properly. I think I have to change the wiring around a little bit.

V8kilr

Sorry man but thats what I was tought at the Installers Institute of Florida.

If you have a more reliable source from which you got your information please feel free to present it.

85rotarypower

V8kilr, sorry for doubting you. I thought about it a lot and your statement makes sense. Check out my thread about "Are a miss and electrical related?". This thread outlines a few problems with the engine and my headunit right now. I'm not going to type it all again, but basically, even when the car is running there is not enough power from the battery and alternator to run the ignition system and my head unit efficiently. If I turn the head unit up at all, it turns off and tries to turn back on, like a lack of power. And if I hit the breaks or turn the running lights on, the head unit doesn't even operate. It might be something as simple as a bad ground (I think it might be now that I think about it), but its annoying the hell out of me.

enigma32

85rotarypower:
first, no hard feelings


second, Yea, it's probably something like a bad ground-- You may want to get ahold of an inductive amperage meter to check out your total draw coming out of the battery (that'll give you a good idea of what's going on)... I'm not sure where you could just borrow one.... They'd cost about $40+ to buy :-( Might be able to watch the voltage meter when you power up the head unit... if it dips then there's definitely a current supply problem....
I've been extraordinarily unlucky with the wiring harness in my S2 when trying other head units too- plan to be tackling it with some real effort sometime soon... I expect to be running into problems like yours.

Good luck :-)

85rotarypower

Untill now, I've been having some good luck with my wiring skills. I think I had better clean up the ground a little and see what happens.

I try not to be a smartass, but at the time I just couldn't contemplate that being true (what v8kilr said). It went against all my understanding of elecricity at the time. I've been thinking about it a lot because it boggles me. I figured it made sense though.

Phiber Optik

iTrader: (2)

Just because your battery is rated at 800cca doesn't mean your going to see anywhere near that amount of current for more then a millisecond.

Attually AMP HOUR or RESERVE rating is the most important for car audio

Most AH ratings are at 25amps, anything rated over 140 minuite reserve is good,

Installing Capacitors without upgrading other insufficient charging systems components will have a detrimental effect on your charging system. The capacitor will be another strain on your charging system

To test if you need to upgrade alternator or batteries, with your car running have your stereo as loud as possible (try playing a 50hz test tone if possible) and use a multimeter to measure the voltage of the system at the battery, if the voltage is below 12.6v your battery will die in the long run, perhaps killing the alternator also. The lower the voltage the faster it will kill the system

Also if your running below 12.6v the amplifier is also strained, because it is trying to output high power from a lower input power which creates more of a strain on the input devices in the amplifier. Some amps will directly blow if you run them at 11v or lower (Earthquake D2 for example)

All the power the is pulled from the battery needs to return to the battery through the ground via the chassis. I highly suggest you upgrade the BIG 3, It should greatly reduce the voltage drop you are experiencing.
Here is a very good link with pics on how-to upgrade the big 3 wires http://forum.sounddomain.com/forum/u...c;f=5;t=007801

For my comptition system I have an 210amp Ohio generator, 1/0awg wiring, stock battery, 2 6volt gelcel 450min. reserve batteries. my amplifier draws 400amps of current without dimming the lights when the car is off!

Capacitors are a band-aid fix and in the long term can be the reason your charging system failed, if you have everything upgraded to handle the current draw capacitors aren't needed

85rotarypower

My problem still doesn't make sence though. I cleaned the ground for the head unit. No change. I wonder if my chassis to battery wire is OK.

enigma32

You should definitely check that.

Maybe try running a temporary wire to the head unit directly from the battery too?

85rotarypower

First off, I did totally custom wiring for my head unit and amp (14 gauge for head unit and 10 gauge for amp). The only wire I used from the stock wiring harness for the head unit was the ignition switch wire (the one thats on with 12 volts only when ignition is in accessory possition).

Anyway, It occured to me after thinking almost non stop for 3 hours that when I turn my e-fan on it doesn't affect the head unit (grounded right to battery, not through chassis). Now I know my e-fan draws more power than the tail lights. And when I hit the brakes the head unit accted up. So I thought about that. I tested my theory by grounding the e-fan to the chassis. Sure enough, when I turned the e-fan on, the head unit acted up. This told me the chassis ground was not very good. So, I went to canadian tire and got some 6 gauge ground wire and put that between the chassis and battery (on top of strut tower). Problem solved.

Moral of the story, don't only check you minor grounds. Check you major grounds too.

V8kilr

I dont understand if you where trying to correct me because it just seems your re-wording stuff I already said.

WanKeL FD RX-7

iTrader: (7)

I'll install the sub and amp..


Finally, i bought a Rockford Fosgate 300s AMP (300w RMS in 4 ohms, bridged mode)

and i bought a Infinity Reference Series 1230W model, 12 inch, 300W RMS...

I changed my alternator last summer for a brand new one, i think it's 70 or 80 amps, i might be okay for now. It was written Mitsubishi on my new alternator... ??

Max

enigma32

My alternators say Mitsubishi on them too....
(yes, all four of them )

I still want one of these in my car....
http://cgi.ebay.com/ws/eBayISAPI.dll...tem=3721509861

V8kilr

WTF

The EVX is a Studio subwoofer, its made for long throw applications.

enigma32

Not a studio subwoofer-- a concert subwoofer

fatboy7

Just a BS (almost an MS) in Electrcal engineering, and a good knowledge of maxwell's equations.

I'd like to clarify a little what I was taking about:

Both the battery and the alternator can be modeled as a perfect voltage source with some non-ideal attached impedance. Impedance is a complex value consisting of resistance, the real part, and reactance, the imaginary part. Resistance can be considered the steady-state part of impedance to current flow, and reactance as the impedance to transients. Ideal capacitors have negative reactance (as they reach steady state current stops flowing though them, voltage mimics the input voltage), ideal inductors have positive reactance(as they reach steady state votage developed becomes zeros, current becomes maximum).

The alternator can be viewed as a 14.4 V voltage source with a series resistor, and series inductor. The resistor limits how much current it can produce before the voltage drops below that of the battery. The inductor makes the alternator try to output a constant current, any quick transient increase in current needed makes the alternator too slow to keep up and again the total voltage it produces will drop below that of the battery. But the alternator over the long run will keep the battery charged, as well as try to provide the average power that the amplifer draws.

The Battery can be viewed as a 12.8 V voltage source in series with a resistor inparallel with a capacitor also in series with a resistor.With the car turned off(ie the alternator off) and the amplifier drawing a constant current (never happens but we can idealize) The branch with the capacitor does nothing, and the voltage seen at the battery terminal will be some voltage below 12.8 due to the drop accross the series resistor. The more the amplifier draws the lower the voltage drop is. When all a sudden the amplifier needs more current it draws it from the "internal" capacitor in the battery model. There is still a voltage drop because the capacitor also has a resistor, and eventually the capacitor discharges and reaches a new steady state.

Now lets turn on the car, to get the alternator going. The alternator charges the battery and is internally regulated to 14.4V. So long as the alternator is able to keep up with the current draw, and the current draw is realatively constant, the alternator powers all the power to the car, and to the amplifier. But the amplifier doesn't draw consant current, because the music it is producing isn't constant. Internal capacitors in the amplifier, external capacitors that can be added, and the internal battery capacitor that the alternator also keeps charged, attempt to keep the voltage constant and provide bursts of current when the alternator is not able to keep up. If these capacitors too are unable to keep the voltage up (due to internal resistances of their own) the battery starts to discharge, and the voltage drops to 12.8 or below. If the average current draw is low, but the transient currents are large the alternator can't keep up, but it doesn't need to be upgraded because it is only the average current draw that it provides. Large transient currents mean you need to add external capacitors, and if severe enough a better battery. If the average current is high than the alternator is providing a large amount of the power delivered to the amps, and the alternator will burn up faster if it is even able to keep the system charged and working properly.

Anyway, back to your statements V8kilr:
I disagree with number 5 but not entirely because the alternator has to deliver the average power or the battery will die. But I mentioned in my previous post that the average power is much lower than the peak power. In the average car system it really only takes 5-10 W at the speakers to make the volume hit 100db, only 50-100W to get to 110dB. Even though most amplifers are only 30-40% effecient that still means it only takes 15-30W rms at 100dB and 150-300W rms at 110dB which is pretty freaking loud to listen to for extended periods.If your bag is ear bleeding SPL 120dB+ than using class A/B amplifiers it can take 1500-3000W. So under normal conditions the alternator is adequate, and provides very little power.Instantaneous power is provided by the battery's internal capacitance. Bacause music is random, it is largely transient and the batter's internal capacitance provides most of the power. So the battery provides most of the power but not all.

I agree with number 6 completely, and even gave evidence to support it.

85rotarypower

You DO NOT want the 18" EVX in your car. Is a concert speaker. Made for high power, low excursion applications. Sure, they are great for low frequencies and have a high power handling, but the box size would be bigger than the cabin of the car. Basically, it would sound like **** in anything smaller than a ford excursion, since you can't put a big enough box in anything else. Its hard enough to get a 15" sub to sound good in a 7 because the box is just too big to fit nicely in the hatch area.

Something that would be more suited for a small box application is this:



This is a Kicker SoloX series subwoofer. Made specifically for high SPL application. But the box size is still too big to fit in a 7 (at least 3 cu ft required). I won't even mention the price ($1299). The biggest I would go in a 7 is 12". It weighs 100lbs!!! and has a peak power handling of 10000 watts!

enigma32

I don't want a high SPL.

You a sound engineer? Can you calculate wavelength and resonance?

I can. And I would plan on using the car as the chamber.
I have very different desires in terms of audio quality from those of most people.