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Subwoofers are designed to deliver thumping bass and so rattling is a common problem with these devices due to the brutal vibrations. However, rattling subwoofers can be fixed quite easily with a few simple tweaks.

Whether you are using your sub in your home theater system or for live performances, subwoofers are integral devices for delivering a full and enriching audio experience. A rattling subwoofer will certainly diminish the quality of your audio and the experience overall.

Subwoofers often rattle when there are loose components within the device, when they are not level, too close to objects, damaged internal components, or if they are overpowered by high volumes or incoming power beyond its limits, or if it’s underpowered due to clipped signals. 

Before we get into it, try some quick fixes such as repositioning the subwoofer if it’s too close to certain objects, remove anything objects on top of the subwoofer, and other obvious fixes. 

How Does Your Subwoofer Work?

Before we start troubleshooting the issue, it may be good for us to pick up a quick understanding of how your subwoofer works. A basic understanding of how subwoofers work will help you diagnose problems faster.

A subwoofer is essentially a speaker designed to play the lowest bass frequencies produced by your stereo system.

parts of a subwoofer
Image Credit – Crutchfield.com

The typical frequency range for a subwoofer is about 20–200 Hz for consumer products. Professional grade options usually go below 100 Hz. For these professional subs used for live performances, it is very important that you inspect these subwoofers before each and every performance.

Regular speakers can have a wide frequency range but often lack the most resonant bass frequencies. That’s where the subwoofer comes in. This is why a subwoofer is never used alone.

A subwoofer is essentially made up of the following components:

  • Voice coil and former: electrically excited – the voice coil is wiring wrapped around a cylinder called a former. When energized, the voice coil reacts with the subs magnetic field which causes it to move in and out to create vibrations
  • Cone: material attached to the voice coil that vibrates due to the movement of the voice coil to produce sound
  • Surround: a flexible ring that supports the cone
  • Backplate: the center of the voice coil gap that sits at the rear of the sub-assembly
  • Spider: a flexible ring that supports the rear of the cone

A subwoofer uses a larger woofer and a built-in amplifier that powers the signal to provide deeper cleaner bass. Most subwoofers are powered, meaning they require an external power supply from an electrical outlet to power a built-in amplifier.

Passive subwoofers do not require a dedicated power supply and use power from an external power amplifier.

In any case, the amplifier will provide a signal to the subwoofer that passes through the voice coil.

Since the voice coil sits in the subwoofer’s magnetic field, the electricity passing through the voice coil will produce an electric field that interacts with the magnetic field of the permanent magnet attached to the sub.

This interaction causes the voice coil to react to the magnetism of the subwoofer and move in and out.

This movement then moves the attached cone in the same manner. The vibrations of the attached cone produce sound.

Why Do Subwoofers Rattle and Vibrate?

There are several reasons why your speakers might be rattling and vibrating. They often rattle when they are underpowered or overpowered or when there are loose components within the device.

subwoofer rattling and how to fix it

In most cases, rattling is caused by the wrong subs, and before you can fix the problem, you can take a few steps to diagnose the issue properly.

How to Find the Source of the Problem

Before you go about fixing the issue, it’s always a good idea to take time to diagnose the problem first.

The first step is to turn on your sound system and preferably play bass-heavy music. Here, you’ll have to play as loud as possible until you start to hear vibrating or rattling.

Here are some quick troubleshooting steps:

  1. Cone Damage: When you can hear the rattling, try inspecting a bit closer to see where the problem is. Your primary focus should be on the sub’s cone. So, if you see a tear or a gap in your sub’s cone, you will need to get that replaced.
  2. Cone Padding Issues: Otherwise, if there’s no tear or gap, then your next step is to gently press the cone to check and see if that stops the rattling. If that stops the rattling, you’ll need to check the padding between the speaker cabinet and the woofer.
  3. Woofer Cabinet Issues: The next step is to check the woofer cabinet itself. Rattling only occurs when there are loose screws or parts. If you find any loose screws or legs, try tightening them to see if that rectifies the problem. It’s also important to note that the cabinet itself could be the issue, so adding more screws can help.

If you dint find the issue with the troubleshooting steps above, it’s time to take a closer look.

There are two main reasons why your sub may be rattling – lose components or over/underpowered. Let’s discuss these factors and how to fix them below.

1. Loose Components

One of the most common reasons why subs rattle is loose components. There are numerous subwoofer components, such as the voice coil, surround, backplate, outer cabin, and voice gap that could be loose and need tightening.

How to Fix Loose Components

  1. Level The Sub: If your subwoofer is unbalanced, this may be causing issues as well, especially if it is placed on some soft of feet. You can use a level to ensure that the sub is perfectly level on the ground. You can even turn the subwoofer onto its side and check the feet on the bottom. Tighten the screws holding the feet onto the enclosure.
  2. Ensure everything is secured properly: Before you do anything else, we recommend that you inspect basic things on your sub to find any loose components. First, check all the screws, and if there any loose ones, make sure to tighten them. Even if you find that they seem intact, just go over them to make sure they’re all ok. Finally, check the grill and make sure it’s screwed down properly. If the screws are loose, the subwoofer may be rattling against the opening in the enclosure. If the sub is in a custom enclosure, check if it’s poorly mounted into its box or enclosure and secure it properly. 
  3. Check the cables: Sometimes something as simple as loose cables can cause subwoofer rattling. Check the cabling connections and ensure that the cables have not slipped out part-way out and are rattling against the jack.
  4. Disassemble the cabinet: If that didn’t fix the problem, you will need to undo all that work. Unscrew the cabinet and inspect the inside for any broken components. If everything is secure in its place, tighten the cabinet, and secure it.

2. Overpowered Subwoofer

If you turn your volume up and it starts to distort the sound, you could potentially overpower the sub and cause it to rattle.

Remember, every subwoofer has a maximum rating that defines how much power it can handle.

If you push your subwoofer beyond its power handling capacity, you risk damaging the sub and of course, it will sound terrible.

This is especially an issue with powered amplifiers and passive subwoofers since these subs must pull power from the amplifier.

Why is this likely to damage the sub?

Remember, when an electrical current is passed through the voice coil, the voltage of this current will determine how far the voice coil moves back and forth.

Too much voltage means the voice coil will move too far forward which can result in tearing the cone and surround.

Similarly, if the voice coil moves too far backward, it can end up crashing into the backplate and may even end up jammed inside the voice coil gap. If this happens, you have a major problem!

How to Fix Overpowered subwoofer

The simple step is to check for the wattage rating of your subwoofers. Make sure not to go beyond the maximum wattage that’s recommended for the subwoofer.

If your amp is very powerful, monitor the volume and gain to ensure that you are not pushing too much power to the sub.

One common mistake people make here is to rely on peak value power as a guide for powering their speakers.

RMS is a better guide to use because it speaks to effective or average power (learn more about RMS power in speakers).

The issue is, not all devices will specify peak power. You may be looking at RMS power on the amp and comparing it to peak power on the sub. In this case, the corresponding peak power on the amp will be more than you expected.

3. Underpowered Subwoofer or Faulty Amplifier

It is also possible to underpower your sub and cause it to rattle. You may be saying sending less power to a subwoofer should not cause an issue, and you are right. Sending less power is not the main issue here.

clipped vs sine wave amplifier

The problem actually really has to do with sending clipped signals to the sub. Clipped signals are detrimental to subwoofers. Not only will they cause subwoofer popping and rattling, but there is a high chance that these signals will damage the subwoofer.

So, what is a clipped signal?

First of all, remember that sound signals are sinusoidal waves. A clipped signal usually occurs when the voltage of the signal from the source is too high for the amplifier to handle.

In some cases, the amplifier may be designed to handle that much power, but the device is defective. Because the amplifier cannot accommodate such high voltages, it simply clips off the top and bottom extremes of the sine waves – or clips the sine wave.

The result is a waveform that is square and not sinusoidal. Now, when such a waveform passes through the subwoofer, it will attempt to move the cone backward and forward at a rapid rate – much faster than the sub is designed to handle.

This rapid movement of the cone can easily cause it to wobble and cause rattling. Worse case, it can even tear the cone or other components such as the surround.

Also, because of the square waveform, the cone will be at the maximum and minimum position for a longer time, much longer than the sub is designed to handle.

Holding the cone still for these long periods takes a lot of energy which may cause it to heat up and over time it may burn all the way through.

Keep in mind that the square waveform has twice the RMS rating than its sinusoidal counterpart. In most cases, these cones tart to unwind and deform.

How to Fix Underpowered Subwoofer

Defective amplifiers spell disaster for your sound system.  The clipped signals created from deflective amps or low power amps can permanently damage your subwoofer.

Firstly, ensure that your amplifier is capable of handling high volume signals from the source and check to ensure that your power amps are working properly if you notice issues with your subwoofer.

If it cannot, then either change the amplifier or simply reduce the volume.

 

4. Damaged Internal Components

Damage to internal components may be caused by a variety of reasons, including overpowering or underpowering your subwoofer.

Here are some common internal issues that may need the expertise of an audio technician:

  1. Coil Wires touching the cone from below: the spider is supposed to support the cone and separate it from the voice coil below. However, clipped signals can cause the voice coil to touch the cone and may even damage it. 
  2. Coil stick in the coil gap: similarly, clipped signals can cause the coil o stick in the voice coil gap of the back plate. 
  3. Magnetic particles close to the coil on the sub cone: sometimes, the magnet in the sub can disintegrate over time and particles may get logged on the coil. When the coil vibrates, the vibrations of these particles is amplified, causing rattling. 
  4. Broken/torn cone or surround: if the cone or surround tears or breaks, rattling is likely
  5. Spider broke below the cone: a broken spider will result in an unstable cone and rattling is therefore likely
  6. Magnet housing not stable: the magnetic housing is an integral part of the sub’s structure. If it’s not stable, rattling is likely
  7. Coil movement not parallel to the magnet: the coil is supposed to move completely parallel to the magnet. Any variations in its movement and you will have issues.

 

Conclusion

As you can see, a simple thing like a loose screw to a complex issue like a defective amp can cause that annoying rattling in your subwoofer.

It’s a common problem that many sound system owners face at some point. Remember, subwoofers are regular audio devices, they are not designed to last forever. Hence, regular maintenance is essential to keep your system in good shape.