Head units and Speakers

Car audio head units in all basic factory car stereo systems Northern NJ have small, built-in amplifiers to power a handful of speakers. Meanwhile, premium factory-installed sound systems usually use larger, more powerful "outboard" amplifiers that are separate from the head unit to power more speakers and achieve better sound quality.

An amplifier is typically buried in the car, you'll rarely see it in an OEM (original equipment manufacturer) sound system like you would a head unit and speakers. But amplifiers are integral components that provide power and volume to your car tunes, and they play an important part in the character of the music you experience in your car. Without an amplifier, you could never experience high-quality music reproduction in your car.

Boosting

Amplifier boosts the low-level audio signal generated by the head unit so that it's powerful enough to move the cones of the speakers in the system and create sound. But before the signal can be amplified, it has to be processed by a preamplifier or "preamp."

There can be more than one preamp component in a complex car audio system. Preamp refers to any stage in the audio path in which the signal is processed before being amplified. The preamp inside a head unit takes the raw signals from the various sources in the head unit, such as the CD player or radio tuner, and sends the low-level output to the amplifier. The preamp stage is also where such tone controls as bass, treble and equalization manipulate the audio signal that will ultimately adjust the sound. When the signal reaches the actual amplifier, its internal-input preamp stage processes it further.

Crossing Over

Part of the preamp processing typically involves circuitry known as a crossover. It electronically divides the full-range audio signal that's fed to the amplifier into separate frequencies. Think of a crossover as an audio-signal traffic cop, directing specific frequencies so they can be reproduced by specialized speakers, such as woofers and tweeters.

Many car stereo systems Northern NJ use two types of crossovers. An active crossover is a preamp component that divides the full-range, line-level signal before amplification so an amplifier or an amplifier's separate channels handle only a certain frequency range for specific speakers. A passive crossover accepts an audio signal after it's been amplified and siphons off frequencies for specific speakers. Passive crossovers are found on "two-way" speakers that have a pair of speakers mounted on a single frame. A two-way 6-by-9-inch speaker that's found in many stock audio systems incorporates a large midrange and small tweeter. In that case, an audio signal will first pass through a small passive crossover that separates the frequencies between the two speakers.

The Speakers

While almost any amplifier will produce around twice its RMS power in peak mode, it's usually with very high distortion. This occurs when the amplifier is pushed to its limits and creates severely distorted sound that can damage a system's speakers. When a car stereo system suffers from distortion, your first impression may be to blame it on defective speakers. But in reality it's more likely caused by distortion from the amplifier. The small amplifiers built inside of head units or even some outboard amps in OEM sound systems are not always up to the task of cranking out tunes at very loud volumes.