For stock cars consider 1000 watt amp at most !

[generalGOTCHA 10+ year member]

There is a lot of confusion about this topic but Ohm's Law can help us here. The amount of current demand your system will have on your charging system depends upon the amp and your listening habits.

First lets look at what your vehicle needs to run. Depending on which and how many accessories you are using, you vehicle will need 40 - 60 amps to operate.

Your amp is rated for 1500 Watts RMS @ 14.4V. Current (amps) = Power (Watts) / Voltage. To figure out how much power an amp rated @ 14.4V would do at realistic in-car voltage, multiply power by .7. (1500*.7= 1050). So lets's plug this into the formula: 1050 Watts/12.5 Volts = 84 Amps.

This is not the whole story hower. The number above assumes the amp is 100% efficient, but it's not. A design like this amp has great efficiency but when you consider the greater levels of clipping the amp will be exposed to it's efficency is about 50%. This means it will need 2100 Watts to generate 1050 (yikes). So lets see: 2100 Watts/12.5V= 168 amps plus the 40-60 amps you car needs, you need a 200 - 320 amp alternator just to feed this one amp....or do you?

You are the other factor. Your listening tastes dictate how much of that availabe power you are going to use with music. Most people will use 20% of the amplifier's power on average with music:

1050*.2=210 Watts (average)

(210*2)/12.5=33.6amps (average)

If you are like most people, you probably will not need to change the alternator if it's healthy.

Abusive poeple will use 50% of the amplifer's power on average with music:

1050*.5=525 Watts (average)

(525*2)/12.5=84amps (average)

Probably should upgrade.

The major difference between these two types of listeners is the amount of clipping they will drive their systems to. Most people will drive thier systems into clipping, some more than others. Clipping dramatically increases average power.

There are other factors that influence average power like Crest Factor of recordings but that is a different discussion.

Click to read more...

 

[generalGOTCHA 10+ year member]

all the information you'll need is contained within my post. Just plug in the numbers that you feel apply to you. It's doubtful you are using 75% of your amplifiers average power with music however...Unless you are driving around listening to sine waves or something of the like! The most abusive people out there will use 50% of the amplifier's power on average with music (volume pegged). These same people will listen to it loud and not care how bad it sounds. The transient nature of music makes this so.

 

[n2audio 5,000+ posts]

if you know how to set gains your amps should rarely clip.

This is the post that put it all in perspective for me.

Excerpt from carsound concerning someone who wanted to put 4kw rms worth of amps in a boat with a 55A alternator.

guys the math is really very siimple------4000 watts is 4000 watts and watts is always volts x amps-----so in a 12 volt system it would be 333 amps and at 15 volts it would be 266 amps--------now if we have to pass that wattage through a lossy system (like an amplifier) we have to account for efficiency losses and add a percentage----ie if the efficiency is 50% we have to double our starting amperage since the voltage is still the same------so a 50% lossy device outputing 4000 watts would draw 8000 watts-------at 13 volts this would be about 615 amps--------class AB amps range about 50-60% at full output and class D amps range about 60-80% at full output------NOW for the biggest factor-------if we are playing music we can automatically divide these numbers by 1/3 or more for short term values due to the crest factor of music and for long term values we can divide by even more-----there are pauses between songs and at the end of the disc where the current demands are VERY low and these affect the long term average quite a bit-----and---sooner or later you are bound to ride by a cop and might have to turn it down a bit-----its not likely that a long term value of more than 10% can be needed for actual power requirements in a real system-------so for that 4000 watt system most any stock alternator will do just fine since it is a rare system that requires more than 50 CONTINUOUS LONG TERM AMPS.............RC

 

[Tirefryr 10+ year member]

And this is NEW news? //content.invisioncic.com/y282845/emoticons/smile.gif.1ebc41e1811405b213edfc4622c41e27.gif

 

[n2audio 5,000+ posts]

And this is NEW news? //content.invisioncic.com/y282845/emoticons/smile.gif.1ebc41e1811405b213edfc4622c41e27.gif

To a lot of people, sure.

 

[Andy4fun 10+ year member]

As I see it, a good battery can give much more peak current then the alternator. How else can my system play loud without the engine running at all. This only empties your battery pretty quick.

 

[generalGOTCHA 10+ year member]

I posted this information , copied and pasted from a JL audio employee without cresting involved.

I figured his words would help give an idea to many who want 2- 3000watt rms systems . RMS systems ! most people purchase a 2000W amp, which is 1000W RMS ...

OH btw //content.invisioncic.com/y282845/emoticons/smile.gif.1ebc41e1811405b213edfc4622c41e27.gif I bench tested my vibe 268 at Custom Sounds San Antonio, My amp on 14v system on a pair of L7's pressed those subs at a nice 154dbs //content.invisioncic.com/y282845/emoticons/smile.gif.1ebc41e1811405b213edfc4622c41e27.gif and bench tested at 923Watts RMS @ 4 ohms very very close to advertised output //content.invisioncic.com/y282845/emoticons/smile.gif.1ebc41e1811405b213edfc4622c41e27.gif and for 156$ ((second day shipping not included)) Ide have to say for the money I am very pleased.

Now for the battery issue. With what was said above ! If I get a high amperage battery I should be ok correct ? also.. at the battery terminals, my system puts out 14.7volts this should be no higher than 14.4 correct ? Less my digital-VOM is in-accurate. Custom sounds told me I should be fine if I got a new battery ... the one in my car would suffice but not reccomended. SO thats what I intend to do.

I will keep everyone current on my Lanzar 268 Viberant series , If it fails, smokes //content.invisioncic.com/y282845/emoticons/smile.gif.1ebc41e1811405b213edfc4622c41e27.gif is reliable etc.. I will keep everyone informed.

This was first time I ever had an amp bench tested .. do they usually charge for these services ?? cost me 20$

Makes me wanna buy more amps to bench test LOL... kinda like adding aftermarket race parts to a car ...

 

[JimJ 5,000+ posts]

154 on what mic? That's pretty impressive...

 

[iamamp3pimp 5,000+ posts]

To a lot of people, sure.

its new to me

and yea i know its a few months old