# when to get a new alt????



## HorseflyofDoom (Aug 21, 2004)

hey i have a 70 amp alternator and their is no whining or anything but i was wondering how much i could upgrade my audio system before i would need a higher amp alternator. right now i am running 2 amps (200rms and 400rms). Would 600 rms of watts be a strain on my alt even though i don't see my lights dimming or anything or would a new alt effect the sound in any way (i.e. sounds cleaner/louder)


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## Punkrocka436 (Jul 8, 2003)

before getting a new alt...some things should happen

1. Turn on everything in the car (all lights, AC, Stereo up loud)...do the lights dim?
2. If yes, upgrade the big three (a simple search for "big three" or "magic three" will turn up something)
3. If that doesnt work, get a deep cycle battery (optima yellow or blue top)
4. If you still have dimming, i would upgrade the alt

At the full 600 watts RMS (which i doubt your getting, unless the gains are turned up all the way...in which case you NEED to turn them down) you are using ~41 amps (Wattage/Voltage= Amperes). At about 900 watts RMS you would be straining your alternator, unless you dont like to ride with lights or AC, and even then its a pretty big load. 

Bottom line, you shouldnt need a new alternator, and you shouldnt need a new one unless you plan on upgrading your system >1000 Watts


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## sr20dem0n (Mar 19, 2003)

even past 1000 watts you shouldn't need a new alt, unless of course you're deaf

I have *cough* over 2000rms in my car, but I never use that much. It's not really about how much power you have available, it's about how loud you listen to your music. You could have a 500rms system and fry your alt, if you were to crank the volume and drive those amps into full clipping that 500rms will quickly turn into a 1500+rms draw on the electrical system. On the other hand you could have a 2000rms system on the stock alt and batt (like me) and never have a problem, because when you're just cruising around listening to your system you're only using 3-400rms at the most, and maybe 800-1000rms if you really start to crank it up to show off or whatever. It all depends on the listener.

Like Punkrocka said, there are steps that you should go through, with a new alt being one of the last steps. If you don't get any dimming you should be perfectly fine, if you do get some then try upgrading the magic 3 and that should fix it right up.


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## captain_shrapnel (Sep 10, 2004)

Just to share my experience....
I built a REAL 2000 watt rms system to push 8 JL 12w3's. I too worried about alternator problems, but after talking with a few local installers, I installed a single Optima yellow top in the back. Having 2 batteries (one close to the amps) made all the difference. No capacitor, nothing more than a ~60 amp alt. The bass hit like a ton of bircks! Clean, clear, LOUD and all without dimming the headlights. High powered alternators are rather expensive, try a 2nd battery 1st. My 2 cents.


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## Punkrocka436 (Jul 8, 2003)

I was saying that if there is 1000 watts playing ALL THE TIME. 

try the big 3 before the battery though


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## potsy (Oct 10, 2004)

*alternator*

Dont be worried about the alternator. What you need is a 1 farad capacitor which will keep the voltage steady to the amps which means less distortion and more power. I heard that capacitors also can save batteries.


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## sr20dem0n (Mar 19, 2003)

no he doesn't need a new cap, and no a cap won't do a single thing to save your battery or alternator


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## Zac (Mar 10, 2004)

potsy said:


> Dont be worried about the alternator. What you need is a 1 farad capacitor which will keep the voltage steady to the amps which means less distortion and more power. I heard that capacitors also can save batteries.


Caps are simply bandaids. Upon getting my system I found this out.


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## Punkrocka436 (Jul 8, 2003)

caps= teh suck


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## JLTD (Oct 12, 2004)

HorseflyofDoom said:


> hey i have a 70 amp alternator and their is no whining or anything but i was wondering how much i could upgrade my audio system before i would need a higher amp alternator. right now i am running 2 amps (200rms and 400rms). Would 600 rms of watts be a strain on my alt even though i don't see my lights dimming or anything or would a new alt effect the sound in any way (i.e. sounds cleaner/louder)


Ohm's Law can help you out here. The amount of stress your audio system can put on your alternator depends upon not only the size of your system, but your listening habits as well.
Your car will need 40 - 60 amps of current to operate. If you have a 70 amp alternator, you have 10 - 30 amps of current available for your system (depending on which and how many accessories you operate). All energy to move a speaker ultimately comes from the alternator. Amplifiers cannot produce more average energy than is available...Nothing will change this!
How much power does your alternator have to give? Power (Watts) = Current (Amps) x Voltage. Using this formula, we can determine that your alternator has 125 - 375 Watts to give.
Amplifers are roughly 50% efficient. Even some higher efficiency designs for subwoofers are only 50% due to the high levels of clipping. This means that your system will need 1200 Watts to produce 600 Watts (yikes). 
Most people will use 20% of the amplifier's energy with music (600 x .2) x 2 = 240 Watts average. If you are like most people, your in the range of your alternators output. Abusive listeners will use 50% of the amplifers capabilities with music (600 x .5) x 2 = 600. If you were an abusive listener, your stock chraging system would not support your habbit.
There may be some who call BS. They are abusive and they have a 1000+ Watt system and it plays just fine. Most amplifiers on the market are non-regulated which means their output will drop as voltage sags. It may work fine, but you are only listening to what the alternator has to give. 


J Colasanti
JL Audio, Inc


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## JLTD (Oct 12, 2004)

HorseflyofDoom said:


> hey i have a 70 amp alternator and their is no whining or anything but i was wondering how much i could upgrade my audio system before i would need a higher amp alternator. right now i am running 2 amps (200rms and 400rms). Would 600 rms of watts be a strain on my alt even though i don't see my lights dimming or anything or would a new alt effect the sound in any way (i.e. sounds cleaner/louder)


Ohm's Law can help you out here. The amount of stress your audio system can put on your alternator depends upon not only the size of your system, but your listening habits as well.
Your car will need 40 - 60 amps of current to operate. If you have a 70 amp alternator, you have 10 - 30 amps of current available for your system (depending on which and how many accessories you operate). All energy to move a speaker ultimately comes from the alternator. Amplifiers cannot produce more average energy than is available...Nothing will change this!
How much power does your alternator have to give? Power (Watts) = Current (Amps) x Voltage. Using this formula, we can determine that your alternator has 125 - 375 Watts to give.
Amplifers are roughly 50% efficient. Even some higher efficiency designs for subwoofers are only 50% due to the high levels of clipping. This means that your system will need 1200 Watts to produce 600 Watts (yikes). 
Most people will use 20% of the amplifier's energy with music (600 x .2) x 2 = 240 Watts average. If you are like most people, your in the range of your alternators output. Abusive listeners will use 50% of the amplifers capabilities with music (600 x .5) x 2 = 600. If you were an abusive listener, your stock chraging system would not support your habit.
There may be some who call BS. They are abusive and they have a 1000+ Watt system and it plays just fine. Most amplifiers on the market are non-regulated which means their output will drop as voltage sags. It may work fine, but you are only listening to what the alternator has to give. 


J Colasanti
JL Audio, Inc


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## JLTD (Oct 12, 2004)

potsy said:


> Dont be worried about the alternator. What you need is a 1 farad capacitor which will keep the voltage steady to the amps which means less distortion and more power. I heard that capacitors also can save batteries.


Capacitors can never charge to a higher voltage than what is available so they do nothing to help an over-taxed charging system.

J Colasanti
JL Audio, Inc


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## sr20dem0n (Mar 19, 2003)

JLTD said:


> Ohm's Law can help you out here. The amount of stress your audio system can put on your alternator depends upon not only the size of your system, but your listening habits as well.
> Your car will need 40 - 60 amps of current to operate. If you have a 70 amp alternator, you have 10 - 30 amps of current available for your system (depending on which and how many accessories you operate). All energy to move a speaker ultimately comes from the alternator. Amplifiers cannot produce more average energy than is available...Nothing will change this!
> How much power does your alternator have to give? Power (Watts) = Current (Amps) x Voltage. Using this formula, we can determine that your alternator has 125 - 375 Watts to give.
> Amplifers are roughly 50% efficient. Even some higher efficiency designs for subwoofers are only 50% due to the high levels of clipping. This means that your system will need 1200 Watts to produce 600 Watts (yikes).
> ...


While I agree with a lot of what you say, there are some parts that rub me the wrong way

*Amplifers are roughly 50% efficient. Even some higher efficiency designs for subwoofers are only 50% due to the high levels of clipping.*
That's only true if you actually drive these amplifiers into clipping, if you let them run in their normal power range they can be very efficient, up to 80-90% in many cases

*Most people will use 20% of the amplifier's energy with music (600 x .2) x 2 = 240 Watts average. If you are like most people, your in the range of your alternators output. Abusive listeners will use 50% of the amplifers capabilities with music (600 x .5) x 2 = 600.*
Listeners don't use a percentage of their amplifier power, they use the power that they want regardless of what the amp is capable of producing. My mom probably uses around 5-10 watts when she's listening to music on her system (cheap clarion headunit and stock speakers, I'm guessing around 15x4), so that means she uses about 15% of her amplifier's power. Now if she sat in my car for a day, her listening habits wouldn't change, my speakers are a little less efficient than the stockers so she might use upwards of 20 watts, which is around 1% of my amplifiers' power. She listens to her music at the same volume, the capability of the system has nothing to do with it. It's not about percentages of the amps' potential, it's simply about how much power is required to drive the speakers to the listener's desired level. People will use anywhere from 1% to 100% (or even more, if you count the people who don't care about clipping) of their amplifier power, depending on how much power they actually have and what mood they're in.

I probably use around 2-300 rms most of the time, which is only 10-15% of my amps' power. Does that mean I don't listen to my music loud since other people use 20-50%? Not at all....


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## Bumpin (Feb 18, 2003)

SR20 what do you think about my setup? LoL how much wattage do you think my tiny little amp is pushin?


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## sr20dem0n (Mar 19, 2003)

I don't know what amp you have


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## Bumpin (Feb 18, 2003)

Orion XTR Pro 2400


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## captain_shrapnel (Sep 10, 2004)

sr20dem0n said:


> While I agree with a lot of what you say, there are some parts that rub me the wrong way
> 
> *Amplifers are roughly 50% efficient. Even some higher efficiency designs for subwoofers are only 50% due to the high levels of clipping.*
> That's only true if you actually drive these amplifiers into clipping, if you let them run in their normal power range they can be very efficient, up to 80-90% in many cases
> ...


SR20demon, I think what the JL tech meant by used percentage of amplifier power is more duty cycle. Unless the amp's input is a pure sine wave, 100% power is not acheived often. Realistically, the nature of a musical waveform is such that full output might be reached only when, say, a kick drum hits. It lasts for a fraction of a second, and occurs every (insert time interval here) during the song. When the power is averaged over the listening time of the song, really what you have is a small fraction of what the amp is rated for. Some amp manufacturers actually rate their amps based on 1/8th power output using pink noise to attempt to address this ambiguous spec.


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## sr20dem0n (Mar 19, 2003)

ah alright, that makes more sense, I didn't think of it like that
I guess then it depends on whether you listen to jazz or lil jon, hehe

Bumpin - that amp's a pussy, I wouldn't expect it to put out any more than 75-100rms


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## Bumpin (Feb 18, 2003)

sr20dem0n said:


> ah alright, that makes more sense, I didn't think of it like that
> I guess then it depends on whether you listen to jazz or lil jon, hehe
> 
> Bumpin - that amp's a pussy, I wouldn't expect it to put out any more than 75-100rms


LMAO! I like you, you're funny...LMAO!


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## JLTD (Oct 12, 2004)

sr20dem0n said:


> While I agree with a lot of what you say, there are some parts that rub me the wrong way
> 
> *Amplifers are roughly 50% efficient. Even some higher efficiency designs for subwoofers are only 50% due to the high levels of clipping.*
> That's only true if you actually drive these amplifiers into clipping, if you let them run in their normal power range they can be very efficient, up to 80-90% in many cases
> ...


There's a lot of confusion on this topic which is why I added the "Some people will call BS on this". 
The reality is most people drive their systems into clipping. Clipping levels of 10 -12dB is not uncommon especially in low frequency (this increase the average power by 4x's). Even golden-eared audiophiles cannot detect these levels with music. I was speaking of average power in my post and clipping dramaically increases average power as does the low crest factor of todays recordings (especially MP3). 
Rememeber the original question was about if the alt needed upgrade. I provided a great "rule of thumb" to make this determination. 
Thanks giving me the opportunity to clarify the position.

P.S.
As far as efficiency and "loudness" goes. Here's an interesting tid bit: The efficiency of a really good subwoofer as a power device is about 10%. This means 10% of the power you apply to it actually makes sound, the rest is heat. Off topic, but I thought you might find it interesting!.


J Colasanti 
JL Audio, Inc


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## captain_shrapnel (Sep 10, 2004)

Yeah, you definetly got that right. Most people will not really consider music "loud" unless they hear a little distortion. It is some kind of psycho-acoustic thing and guess it is related to the compression of musical peaks into a narrower dynamic range. A good example of this is radio. When I hear a song on the radio, it seems to sound thicker and somehow louder than when I listen to a copy on cd. I finally figured out that its because stations actually add further compression to prevent their transmitters from clipping. Interesting stuff.

SO when is JL going to address the voice coil efficiency thing (10%) and get revolutionary? Or anyone for that matter? The only company I know of that did something different is Servodrive (used a servo motor in place of a voice coil). Anything on the drawing board? Just curious...


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## sr20dem0n (Mar 19, 2003)

Pheonix Gold had their cyclone subs, I think they were up around 10-15% efficient (most subs are closer to 3-5%, all box and driver dependant though), but they didn't stick around for too long.


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