Any quality car audio installation must include the electronics: amplifiers, speakers, and cd player. It must also contain damping materials for road noise control and acoustical treatment inside the car itself to minimize interior surface reflections.
The electronics in any car audio installation must include amplifiers. One can obtain amplifiers that will do stereo or multiple channel speaker systems. This arrangement will work well for the middle and high frequencies, but another separate amplifier is needed for the subwoofer. The subwoofer or subwoofers will need their own power source in order to provide the power requirements a subwoofer needs without taking any energy away from the middle and high frequencies. A subwoofer power requirements can take needed energy away from the transient coverage, so needed for quality sound in the mids and highs.
Car audio installation must include damping materials placed in the floor and door panels that can minimize road and wind noise which causes vibrations that translate to increased ambient noise levels inside the cab of our vehicle. This increased ambient noise floor is the reason we turn up our gain control when we are moving and then have to turn it down when we come to a stoplight where there is no road noise from tires and no wind noise from air rushing over the exterior vehicle surfaces. Well, some of us turn it down at stoplights.
Acoustical treatment inside the cab of our vehicle should be a part of any quality car audio installation. Energy reflections off of the glass surfaces in our cars and trucks must be minimized in order to try and create some type of quality sound. The absorptive material manufacturers put inside the vehicles is usually limited to carpet, headliner, and seats. The amount and absorptive qualities of these materials is not enough to control the reflections off of the windshield and rear and side window glass surfaces. Our company test vehicle has speakers installed by the manufacturer that are 2″ away from the windshield. With this type of installation, we need to wear sunglasses for both our eyes and ears.