When it comes to subwoofers, the question of whether or not it is worth repairing them is a common one. In most cases, the answer is no. The cost of repair can often be more than the cost of a new subwoofer, and the new one will likely work better. However, if you have a sentimental attachment to your subwoofer, you may still want to try and repair it.
If you decide to repair your subwoofer, the first step is to identify the extent of the damage. This will help you decide if you want to buy a new one or try to repair it. The most common cause of speaker failure is a short circuit in either the wires that provide the signal or in the subwoofer terminals. If you decide to repair your subwoofer yourself, you will need to be patient and follow a few steps.
First, heat the cap with a hair dryer and then remove it carefully. From behind, spread some wood glue and then place a small piece of tissue paper over the crack. Press down and let the glue dry for an hour. Once the glue is dry, you can replace the speaker in your car. Yes, it is possible to repair a damaged subwoofer yourself with a thorough investigation of the root cause of the problem (and the consequent replacement of the part).
Alternatively, you can take it to a local audio store and have it repaired for you.