Listening for Damage
1、Turn on the vehicle. Most vehicles need to be turned on for the audio system to play. Unless your car is particular, you won't need to fully start the engine, which would only waste gas.
2、Insert a CD or mp3 device with a full sound range. Pick something that you play often in your car, so you know what to listen for. This will help you spot anything that sounds unusual. You could also pick a song that has a clear and familiar bass line.
3、Turn the volume to an appropriate level. If the audio is too low, it will be hard to tell if you have a blown speaker. This doesn't mean that you should blast your whole neighborhood with your tunes to diagnose your vehicle.
（ Adjust the treble and bass, if necessary. Make sure that their levels are equal in the twelve o'clock position. When you hear a lack of range, it might just mean your system isn't equalized properly）
4、Recognize distortion. If you have trouble recognizing distortion, play a track on headphones or on another device. Then, play that same track through your car's sound system. If you hear crackles or the song sounds slightly muffled, one or more of your speakers might be blown.
（ Listen for rattling. If the speaker is blown, you will likely hear a shaking, rattling sound）
5、Listen for a lack of range. If a certain bass, mid, or high speaker is blown, you will notice certain registers don't come through. This is easiest if you are familiar with the song, and know what to listen for or expect
6、 Isolate the speaker. If possible, use your audio system's fader controls to attempt to isolate the faulty speaker. By narrowing down one section of the car, you'll have a better chance of determining which speaker is blown. Always try to isolate the problem so you don't overspend and replace the entire system.
( Use the pan function to switch the sound from left to right. When panning, go 100% to either the left or right side to fully isolate it. Use the fade settings the same as the pan setting. Go 100% to the rear or front of your car.)