(SOLVED) Subwoofers Make Loud Noise When Turned Off

Norvan Martin
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In this guide, we will be exploring the troubleshooting steps to take if your subwoofer is making a loud noise when turned off. This can be pretty alarming, and you may wonder whether it means something is wrong with your equipment. Don’t worry, we will be looking at the likely causes and explaining them in detail.

The main reason for this problem is the factory amp sends a signal to the speakers after you turn the car off for a period which causes your Line Output Converter (LOC) to think you are still playing music which keeps your speakers on with just noise as its signal which causes the hum.

There are many other reasons your subwoofer may make a loud noise when truned off; such as a sudden surge in power or energy, loose input connections, clipped signals, incompatible amplifiers,  and a defective power supply. There are ways to fix this issue, like reducing volume, switching the subwoofer at last, using power strips, and more. 

In this article, we shall discuss the following:

  • Causes Behind The Loud Noise
  • Does The Loud Noise Mean Something Is Wrong?
  • Can The Loud Noise Be Avoided?: Steps To Prevent It

Let us see what could be the possible reasons behind this:

1. Line Output Converter (LOC) Issues

One of the main causes of this issue is the LOC continuing to get a signal after the car is turned off which keeps the amp on.

Fix: To fix this, you can splice your LOC’s 12V wire into the accessory wire and connect it there instead of having it wired where the power wire connects to the amp.

You can also try the following fixes:

  • Use a ground loop filter
  • Lower your frequency (defeats the purpose of having an amp)
  • Set the input switch to RCA, lower the input volume of the speakers on the LOC, and lower the crossover on the amp
  • Lower your bass on the radio and the input on your LOC

1. Energy Surge Issues

The noise you hear after turning off the subwoofer is caused by a sudden release of energy stored in the subwoofer’s capacitors. The moment you turn them off, the capacitors discharge quickly, creating a sudden surge of energy that produces this jarring sound.

Subwoofer capacitors

This happens because the subwoofer is designed to filter out low-frequency sounds not heard by human ears. The capacitors store the energy needed to produce these low-frequency sounds. When the energy is released, a loud sound is produced. 

Fix: Turn the subwoofer off and disconnect the power. Next, press the power button for 30 seconds to a minute with the power off. This way, the subwoofer’s driver stops before the power is disconnected and the capacitors will be discharged. Also, you can try using a power conditioner that will regulate the voltage. 

2. Fault In The Components

If there is a problem with the design or internal parts, then some issues may arise. If the amplifiers are faulty or the connections inside the system are incorrect, a loud sound may occur. Not only this, but it will create more issues in the future and can quickly stop working over time. 

Fix: After adjusting the audio input, an AV receiver should cover all pre-out jacks. If it doesn’t, there’s a good chance the circuitry or a diode is broken.

Reduce your sub’s bass setting first. This is done merely to lessen the jarring sound’s volume. After that, you can manually adjust each input signal. Instead of using the auto-detect selection, it will receive the audio signal. Your AV receiver’s type will determine what you can do.

Ensure the remote subwoofer control is operating correctly.

3. Power Supply Issues

Active subwoofers have internal amplifiers and power supplies. If the subwoofer is not getting a proper power supply, this is bout to happen.

Subwoofer power supply

In addition, if there is a problem with the power supply, such as a faulty capacitor, it could cause the subwoofer to produce noise.

You will experience noises that will bring discomfort. Also, another reason for this noise is if the cables and wiring inside are not of good quality.

Fix: Ensure that you are providing adequate power to your subwoofer. The subwoofer’s power outage should be the same as the amps. Investing in a voltage stabilizer, like a condenser or a power conditioner, is a great solution. In this case, you may need to have the subwoofer repaired or replace its power supply.

4. Issues With Auto-On Settings

Many amplifiers have an auto power-saving feature that turns off the amplifier when there is no audio signal detected for a certain period. Frequently, auto-on settings can cause your subwoofer DSP to turn off suddenly before your amplifier. As a result, the subwoofer makes strange noises when it first turns on.

Fix: You might need to turn off the auto-on option on your subwoofer. It’s a straightforward fix that has shown positive results for many. As a result, it uses less electricity, and the interior temperature consequently drops as well.

5. Amplifier Issues

Sometimes, the amplifier may experience some type of fault due to a defective component, improper grounding, or other internal issues. In such cases, you may need to have the amplifier repaired or replaced.

Fix: Here is how you can test the amplifier in case you do not have an extra subwoofer. Use a functioning RCA connector to connect your subwoofer. First, lower the output of your subwoofer. Then play something on the DVD player while gradually turning up the subwoofer amplifier’s volume. The volume should rise until the music is audible.

If you hear a strange sound, like a pop or humming, the problem is with the subwoofer amplifier. In this case, you must show your speaker to the service center. 

6. Ground loop interference

Ground loop is a phenomenon that occurs when multiple devices are connected to the same audio system, and each device has its electrical ground. This often leads to unwanted interference resulting in buzzing or humming sounds.

Fix: Try using a ground loop isolator.

7. Investigate The Parts: Cables And AV Reciever

This problem can be caused by disruptions in the connection caused by damaged cables and AV receivers.  

In the case of damaged cables, replace them, or check for the connections if they are loosely connected. If the issue vanishes, then you know the cables were causing the issue. 

In the case of AV receivers, connect with a spare receiver and check if the sound vanishes. 

If the sound does not diminish, then the problem lies somewhere else. 

Fix: Like issues with the amplifier, issues with the AV receiver can cause strange noises as well. Swap out the AV receiver or have a technician check the device.

Frequently Asked Questions

1. Can a subwoofer burst?

When the subwoofer experiences short bursts and is played too long, it can damage the equipment. Also, check for any issues with the signals, as sometimes they can also lead to your subwoofers bursting. Ensure the signals are not distorted. 

2. What are the reasons behind a completely damaged subwoofer?

  • Getting clipped signals
  • Receiving too many signals
  • Overloaded power. 
  • Excessive pressure.
  • Not resolving issues at hand and prolonging any minor problem.  

3. What is the life of a subwoofer? How long can they work?

A good quality subwoofer from a trusted brand can last up to eight to thirteen years if used properly. Sometimes, when you do not fix any problems you are facing, the subwoofer’s lifetime may diminish, and it can stop working altogether even before it reaches its maximum life.

4. Does the Loud Noise Mean Something Is Wrong?

The sound you hear does not necessarily mean something is wrong with your system after you switch it off. It is common in most subwoofers and is not a cause for concern. However, if the pop sound is accompanied by some other problems, like distortion or a decrease in sound quality, it could indicate an issue with your equipment.

Besides the sound, if you notice some other problems, it is recommended that you get your subwoofer checked by a trained expert. They can diagnose any issues with your equipment and recommend the necessary repairs or replacements.

Conclusion

To summarize, here are the different ways to fix the issue:

  • Fix the energy surge.
  • Check the audio inputs and change them.
  • Track the power the subwoofer is receiving.
  • Test your amplifiers for any faults. Check for clipped signals. 
  • Investigate the cables and the AV receiver.
  • Disable the auto-on setting.

In addition, if you are experiencing popping or crackling noises with your subwoofer, check this guide. If you are having this issue with your speakers, check out our article on car speakers making static noise when the radio is turned off.

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Norvan Martin is the founder of BoomSpeaker.com. He is a professional Electronics Engineer and is passionate about home theater systems and AV electronics. BoomSpeaker was created as an online hub to share his knowledge and experiences as it relates to home theaters and home audio electronics. My email: [email protected]  Connect on Pinterest and Linkedin