Someone plz clearify


Bronze Member
Username: Perrydog

Flint, Michigan USA

Post Number: 19
Registered: Jan-05
i just hooked up to 12' subs in my 1989 blazer and now when my bass hits my lights dome lights dim, someone plz tell me in english and terms i can understnad why this happens and how to fix it and how much it ususally runs

Bronze Member
Username: Jonny_987

Post Number: 15
Registered: Dec-04
hav a read of this thread, it should help:

Bronze Member
Username: Perrydog

Flint, Michigan USA

Post Number: 22
Registered: Jan-05
ya iv red it and i dont understand im 16 yrs old will sumone put it in my terms

Battery gives you electricity to start your engine.
Once the engine is running, the alternator (like a generator) creates electricity for your engine to run and to power things like your stereo and lights.
Your alternator might be the 105 amp version. (you'd have to check)
With your lights on, when the bass hits, your blazer is using more than 105 amps, so it can't power your lights at full power. The light dims.
To fix this and keep your system, buy an alternator for your blazer that is a higher amp model.

Island Headhunter
Unregistered guest
Bass go boom
Wake up Engine God
Engine God not happy
Engine God make light tremble
Engine God demand money sacrifice
You sacrifice money for a high output alternator
Engine God happy
Engine God make light tremble when bass go boom no more.

Gold Member
Username: Glasswolf

NorthWest, Michigan USA

Post Number: 7279
Registered: Dec-03
The Engine God likes v1rgins, too.

Alternators and Charging Systems

Upon reading and answering many questions about car audio, one question always pops up:
"Do I need a high output alternator or just a capacitor?"
If you want a killer system, you may think that all you need are big amplifiers and huge speakers. Not so! Adding a bunch of car audio components to your vehicle without the proper charging system may lead you to disappointment, distortion and damaged equipment.

Let's say you install a 1,200 watt amplifier in your ride. Your rides charging system must produce enough electrical current to run the amplifier. Now how do you know how much current is needed? Simple: divide the RMS power rating of the amplifier by the amount of voltage your cars electrical system will produce then add in amplifier inefficiency based on amplifier class.

Most vehicle electrical systems are 12.5VDC at idle, and between 13.8 and 14.4VDC above about 900rpm but we use 12 volts as the standard for these calculations, so 1,200 watts divided by 12 volts equals 100 Amperes of current. If this is a class D amplifier, it'll be ~80% efficiend, so we'll add 20% of 100A to the total, and we get about 120A of current demand continuously at peak amp output. This means that the electrical system of the vehicle will need to produce an extra 120 Amperes of electrical current to power your amplifier and subwoofer at peak levels. Keep in mind that the factory electrical system is designed to produce enough charging power (alternator and battery) for the vehicle's stock equipment, and was not designed to accomodate high-powered audio systems.

The biggest mistake made by consumers and (some) installers is failing to beef up the charging system to handle the extra load of the audio system. First, you need to understand how the electrical system operates. This must be one of the most mis-understood systems of the entire vehicle, so here's a brief summary:

Turning the ignition key begins the process of cranking the motor. The battery supplies the power to get things started. Once the engine is running, the electrical burden is shifted over to the alternator. The alternator uses the engine's mechanical power to produce electrical (AC) current. The AC current is passed through a rectifier and changed to DC current which is then sent through a voltage regulator to smooth out and set the voltage rails for the car . The alternator also has the duty of recharging the battery after starting the vehicle by providing a forward bias voltage higher than that which the battery produces on it's own.

Everything works perfectly so long as the power requirements of the vehicle do not exceed the capabilities of the alternator. If the peak output is surpassed due to excessive load, then power will be pulled from the battery. If the alternator and battery combined cannot meet the demand, then the vehicle's voltage rails, and subsequently the electrical devices are diminished (dimming lights, spark plug misfires, audio distortion and amplifier clipping, or even the car stalling.)

The first place to look to determine if your charging system is up to the task is the alternator itself. If possible, look for the HOT RATING on the alternator. IF you can't see it easily, call a local auto-parts store or car dealership and ask them to look up the stock alternator size, or rating for your vehicle. The hot rating will tell you the amount of power the alternator will produce once the engine reaches it's operating temperature (this is a lower rating than the cold rating). I suggest using your stock alternator unless you experience problems. That's how you know if you need to upgrade, since there is no concrete way to tell if a stock alternator has enough reserve to handle your additional burdens. Now, if you do need a new and larger alternator, after finding the stock rating, then allow your alternator about 10 Amperes credit or buffer area.
As a note, when calculating your required current for your audio system, this is an easy way to do it:
1: calculate the total RMS wattage of your system based on how the amplifiers are wired (2 Ohm load, 4 Ohm load etc)
2: take that total RMS rating, and divide by 12 (volts.)
3: add 20% for class D and T or 40% for class AB. (this compensates for efficiency based on amplifier topology)
4: add amplifier totals together for a combined measurement. (in amperes)

This is how many Amperes your audio system will require in addition to what your car already needs (stock alternator rating) at full output.

For more information on charging systems and alternators, see here:
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