Car speakers produce sound by vibrating, or "buzzing," and when operating properly the buzz in not audible. If the buzzing is elevated to a level where it can be heard, especially over the sound of the stereo, it is usually an indication of damage to the speaker membrane. If the membrane, the paper cone that forms the shape of the speaker, develops a hole or tear it will vibrate excessively, causing an audible buzzing sound. Fixing the buzzing in the speakers in your car can usually be accomplished by repairing the damaged area with rubber cement.
Remove the speaker cover by removing the retaining screws or clips, if so equipped, and gently pry off the cover.
Clean the membrane, carefully, with a damp cloth.
Inspect the membrane for damage, looking for cracks, tears or holes that can occur from an object falling on the speaker, or over exposure to heat.
Turn on the stereo and very gradually increase the volume while watching the membrane. Any damaged area should become apparent as the volume, and membrane vibration, increases.
Disconnect the speaker from the power source by disconnecting the negative battery cable.
Apply the rubber cement so it thoroughly covers the damaged area. Allow to dry according to the manufacturer's directions.
Reconnect the power and turn on the stereo to determine whether the buzzing has been resolved. If not, apply a coat of nail polish over the cement patch.