How To Fix Car Subwoofer Thump When Turning Off Or Starting Up Engine

Why Does My Subwoofer Thump Loudly On Startup?

If you hear that the car subwoofer installed into your car makes a thump sound on the startup when turning on the vehicle engine, it is audible because the amp is turning on sooner than the stereo. This causes a small spike in the voltage down the RCA cables making the car subwoofer go thump when turning off. Sometimes cheap amplifiers that are not so expensive tend to have subwoofer popping noises when turned off because of the poor delay circuit inside. Before your start troubleshooting any further make sure all the speakers wires, RCA cables, power and ground cables are connected firmly and well secured from shorting out with each other. Once you have checked all of them and still the thumping sound still is persistent, you can go through the provided solutions to help you resolve this particular car audio related problem.

Please be aware this guide is not intended for fixing subwoofer popping with home theatre setups as they work differently. I want to share this with you guys because this information is very informative, as it helped me and my buddies with our Honda Civics.

Check the ground for poor electrical contact. If the ground is not a clean connection this can cause the car subwoofer to thump when turning off or during startup. So just to make sure, sand down the grounding location so that only bear metal is showing. Any paint or grease left on the car were the black thick ground wire is connected onto can cause these weird noises to appear.

Its Natural for some car headunits to make that popping noise. If this is the case then you can fix this problem by connecting the blue remote turn on wire that goes all the way to the back amplifier instead to the accessory fuse location. This allows the car amp itself to be controlled by the vehicle and not the radio CD player causing the loud thumping sound to eliminate it completely.

Add a cheap relay circuit to amp turn on wire. A relay is an small durable electronic device that uses an electromagnet which is switched on by a signal controlled by a open or closed circuit. This connected inline will stop the car subwoofer from thumping because it will cause a slight delay for the amp to turn on after the headunit has powered on. You can buy these already made or you can build them cheaply yourself with certain components, a new PCB and a soldering iron.