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Old 11th July 2009, 02:19 PM   #1
flyracing1 is offline flyracing1  United States
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Join Date: Jul 2009
Default I have two questions.

I am curious about an amp i am about to buy.
It has it's "rms" rating at 14.4v. Does my car constantly give this power, or does it vary between 12 and 14.4 ?

Also as i was playing with a volt meter the other day, i noticed that when my car was running it said 14.2 on the battery and on the - & + on the amp with it off, then when i turned the stereo on, i seen a drop of 1 or 1.2v on the battery, is this normal

Any help is greatly appreciated.
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Old 11th July 2009, 05:33 PM   #2
mda185 is offline mda185  United States
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You are correct, your car runs between 12 V and 14.4 V depending on the loads on the electrical system. It is normal to see a voltage drop when you first turn on the stereo if you are running high power amplifiers. Your alternator should kick in to increase the voltage if it drops too low. I don't know at what set point most alternators kick in but it should not be below 12 V. If your voltage drops lower than 12 V, there is a problem.
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Old 11th July 2009, 06:49 PM   #3
1moreamp is offline 1moreamp  United States
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13.85 (hot) to 14.4 (cold) volts is a good steady charging rate for your 12 volt car battery. Anything less means you have exceeded your alternators output capacity at that RPM and are relying on battery power to hold the system up at the 12 volt level.

Car Audio Golden rule number 1:
"You have to have power to make power in car audio"

Hence why you see all those big aftermarket alternators and heavy wiring and add on's galore to stabilize what is typically a system that was not designed to handle high powered audio gear.
The stock car charging system was designed to operate the car as built, and not much more.
If your seriously adding on a bunch of high powered audio gear then you have to look at adding on to the charging system to help cover the power demands that bumping down the street require.
Thirty years of watching this industry sell itself and all that time so little emphasis was placed on the one simple fact above < "You got to have power to make power" >....Good luck on your efforts....
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Old 11th July 2009, 07:19 PM   #4
flyracing1 is offline flyracing1  United States
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Thanks guys.
I definately appreciate your help
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Old 11th July 2009, 09:11 PM   #5
flyracing1 is offline flyracing1  United States
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OK, so wait a sec.
If i am running an amp that is rated at 1100w RMS @ 14.4v
Then i heard i should expect 800rms @ 12v, which is what i need for my 2 12" subs.
Would i expect to let the smoke out of my subs when the altenator kicks on to charge the system.
I know a little about car stereos, well, enough to do the wiring myself.. ( It's the best part about it. IMO ) but, havin a hard time grasping this concept......

BTW, the amp i am looking to get is a
US Amps Xterminator Series 1600.2 ( 1100w rms @ 14.4v- 800 dynamic power )
I am not trying to turn this thread into a "should i get this amp?"
because you guys answered my questions very well
but, i really want to understand what i should expect performance wise with a stock charging system, maybe a big three upgrade. so i guess that is the question
should i get this amp ? lol...sorry....
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Old 11th July 2009, 10:25 PM   #6
sakellogg is offline sakellogg  United States
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i started in car audio...got to old to climb under dash sidways and upside down.
i just got done testing a 200w amp on 100wrms max speakers yesterday to earbleading levels, and my speakers are fine.
worry about not enough, and amp clipping before to much. if you look @ home audio speaker specs say paradigm studio 60....rated for 180w max ....amp recomended 80w-200w
you should be fine. when i installed car audio i sujjested @ least 20w over.
I'm not crazy, my mother had me tested
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Old 12th July 2009, 12:13 AM   #7
tsmith1315 is offline tsmith1315  United States
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Originally posted by flyracing1

Would i expect to let the smoke out of my subs when the altenator kicks on to charge the system.

The alternator is much like an electric motor in reverse. The rotor is a coil of wire wound around a spindle, the stator is a group of coils wound into the shell that surrounds the spinning rotor. Battery voltage is pulsed through the rotor at a regular rate and fairly constant current (determined by the coil resistance), and that induces an AC current into the stator.
These pulses of DC are controlled by the voltage regulator, and are present to some extent as long as the engine is running. The alternator's DC output voltage is higher than the battery voltage, and the electrical system primarily runs off the alternator while the battery acts much like a capacitor as storage for transient current demands.
As the battery voltage is pulled down, the voltage regulator increases the duration of the pulses through the stator. The alternator produces more current as a result. As voltage goes up, the regulator reduces the pulse length and current delivery goes down.

This process is a never ending cycle, and is in a constant state of change as current demands are constantly changing. So there's not a point where the alternator actually just kicks in, it's always there and responding to changes.
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Old 12th July 2009, 07:04 AM   #8
1moreamp is offline 1moreamp  United States
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Expect saggy spongy bass unless you have a good solid constant 13.85-14.4 volts of power to the amp at all times. < Internal energy storage of the amp itself can affect this, but none I have seen made recently have very much power storage built in, they expect you the end user to make the power available to the amp, so the internal power supplies can swiftly correct for any demand needs your audio tastes may dictate.
The power demands that the battery meets are chemically slow by comparison of what the alternator can do speed wise on power delivery.
And the typical small group car battery (60 to 70 amp-hour typical) can only be expected to handle so much of a load before the whole system drops back below 12 volts to like 10 volts where most amps just cut off.

Until you load your charging system either by installing all this gear or by going to a real 12 volt shop and having it tested for capacity at idle and above < like typical 35 mile plus cruising speeds > you will have no idea of how all the new gear will drop your stock charging system.

but you can count on one fact of life, "Your car was not built to run anything above 500 watts at 13.85-14.4 volts" >
No auto maker takes such things into account unless you get a aftermarket vehicle like a police car or a ambulance that has been setup for the extra power demands of all the extra gear that sort of industrial vehicle is expected to have in it.
Stock cars are built to power only what the factory installed and maybe a few cigarette plug options, or you would have extra power terminals located thru out the car to begin with.

I myself have a 250 ampere HOT rated alternator and two car battery's < one for the car and one for the system> and my little 1300 watt system can pull 100 amperes at idle without a second thought, and so my alternator is setup to deliver that current at idle also with speed increasing pulley's and extra heavy duty 24 volt diesal alternator rewired for 12 volt operation.
End result I see very little power sag issues, and light dimmimg. And my amps run cooler and more reliably rarely if ever do I see a thermal cutoff. And I have amp life in excess opf 5 years before service, and my battery life is about 2 years under such loads day in and day out. Oh and I did all this to my Suburban which had a stock 140 amp alternator, cause with dual AC setup the SUV could not maintain 12 volts at idle with the air on during a hot day STOCK.

If you wanta bump, your gonna need power under the hood. Leaving things stock does not make sense from a reliability stand point of logic and thinking.
And with all these Chinese built Super power amps and everybody "thinking" they need 1100 watts of bass power inside the cab of a small car, your most likely going to run into reliability issues with either the gear or the car, or both.
Whipping the charging system for that much power and not beefing it up is just calling for trouble.

I call them like I see them, and I been doing this since 1975 when I ran home gear in my Chevy van way before the entire car audio industry as you see it today was even born.. lol lol Yes i am that old and still blasting my tunes in my ride...lol lol lol..I have killed alternators and battery's galore in my life before beefing my own ride up for the onslaught of Pink Floyd at 75 MPH with all the windows down here in Cali. Again I wish you the best of luck on your new system...
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Old 12th July 2009, 05:09 PM   #9
flyracing1 is offline flyracing1  United States
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Beautiful information, guys.
freakin beautiful. been asking these question on other forums for awhile now, with no luck.
You guys, and this site rocks. You will be seeing me around.
Hopefully i can help someone else out one of these days.
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Old 12th July 2009, 05:09 PM   #10
flyracing1 is offline flyracing1  United States
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Join Date: Jul 2009
US Amps " Chinese Super Amps "......really ?
Not made in the US ?
I was lead to believe this was a outstanding amplifier !
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