The speakers that come with your car are generally pretty awful unless you shell out some cash for a better set. Additionally, not all cars come with an auxiliary input for plugging in your smartphone or MP3 player. If upgrading is not an option, or you just don't want to spend the money, here's a fairly simple DIY project that can bring better audio to your car.You might be asking yourself why you'd bother doing this, and the answer lies in your particular situation. The most broad reason would be that you just want better audio, have some decent computer speakers lying around, and don't want to pay for an upgrade. You may also not have an auxiliary input in your car, don't have a tape deck for a tape deck adaptor, and find the FM transmitters to be overpriced and useless. You may also be in a situation where you'd love to pay for an actual upgrade but you're leasing your vehicle and can't perform any permanent modifications. If you fall into one of these categories, this is your solution.
Instructables user misteravocado5 put together a serviceable car audio solution for $US24 by taking a cheap pair of computer speakers, a car power adaptor, a stereo plug, and a few other items. All you have to do is break the speakers out of their casing and do a little rewiring. If you're comfortable with some mild soldering work, this should be a pretty simple project for you to pull off. Check out the Instructables post for a full list of what you'll need and how to put it all together.
Cheap and Easy Car Speakers [Instructables]