A car subwoofer is a specialized speaker designed to reproduce low-frequency sound waves that enhance the overall audio experience in a car. They come in various sizes, including 8 inches, and can be installed in different parts of the car. An 8 inch car subwoofer is a popular size as it provides a good balance of bass and clarity for most car audio systems. 

Some of the advantages of using a car subwoofer include improved sound quality, enhanced bass response, and a better overall listening experience. The key characteristics to look for when choosing a car subwoofer include power handling capacity, frequency response, and sensitivity ratings.