After-market car speakers can enhance your music's vibrant highs and lows with specialized tweeters (responsible for highs) and subwoofers (for lows). Or you can improve the whole range of your audio system by upgrading your car speakers more generally.
Usually sold in pairs, coaxial speakers pack multiple components, such as tweeters and woofers, into each unit. They work as single-source speakers for the full range of frequencies, providing an even sound field. Most designs are two-way speakers (tweeter and woofer), but some are three-way with a tweeter, mid-range driver and woofer in each speaker.
By contrast, component speaker systems offer you the option of separating the tweeters and woofers in your setup, allowing you to place them in your car more flexibly to achieve your preferred sound. Installing your tweeters near head level usually results in clearer highs.