Factory/OEM (Original Equipment Manufacturer) Speakers
A lot of vehicle manufacturers spend as little as possible on the research and development of the interior acoustics and sound quality inside their vehicles. This is usually attributed to the manufacturer's primary concerns with the vehicle's looks and performance. Speakers that are provided to you with a new car purchase are usually poorly constructed and can only handle about 15 watts of power. This is not always the case, but often is. Here is a snippet from Jason Syner's book, "How to Install Automotive Mobile Electronic Systems":
Most speaker options provided by manufacturers are full-range drivers, which play all midrange and high-frequency information out of a paper cone. Some of the more expensive manufacturers in high-end models of certain cars provide a component speaker system for their cars. This system consists of a midrange speaker and separate tweeter speaker. The tweeter is typically mounted in the sail panel above the door panel or in the A-pillar. The midrange speaker is usually mounted at the bottom of the door panel. The tweeter will be aimed at the passenger's ears at a 45-degree angle to improve the high-frequency response. Because high frequencies are directional, pointing the tweeter toward the ear will make higher frequencies sound clearer. The midrange is usually mounted flat to the inner door skin. Some auto manufacturers provide a digital equalization of the sound inside the car. Most auto manufacturers have Digital Signal Processing (DSP) built into them. DSP uses complex algorithms to improve the sound within the car.
Syner, Jason. How to Install Automotive Mobile Electronic Systems.
Minneapolis: MBI Publishing Company, 2009. Print.