How to Tell if a Subwoofer is Blown?

You’re enjoying your home theater system and realize the bass starts sounding distorted, very soft, extra loud, or strange.

Maybe you’re getting no sound at all from your subwoofer. Should you conclude the sub is blown? Not necessarily. 

You can often tell if a subwoofer is blown by checking if there is no sound at all or if the sound is distorted or scratching as well as popping and crackling sounds. You should also check that the cone and voice coil are in proper working condition. 

Read on for more details about the simplest ways to test whether your subwoofer is blown or not and more.

Simple Ways to Test if a Subwoofer is Blown

When you suspect your sub has blown, you should start by fully assessing if there is any damage to determine the exact nature of the issue. 

Here are the three ways to help you analyze the damage thoroughly and determine whether your sub is blown or not.

1. Check The Sound

The quality of sound you are getting is an indicator of the degree of damage. Here are the results you can get, depending on the degree of damage:

• No sound: This might be a clear indication that your subwoofer has completely blown. Before jumping to this conclusion, ensure you properly test the audio source and cables as well as ensure the sub is powered. Here are some fixes for situations where your amp has power but your subwoofer is not working. If they are working correctly, it’s safe to say the sub is completely blown.
• Partial sound with distortion: A weak, distorted sound could mean you have a partially blown sub.
• Scratching sounds: This sound normally indicates that damage has occurred to the cone and you should replace it.

2. Test the Cone

Remove the subwoofer grill cover if t has one and gently push the cone from both sides to see how it moves.

Subwoofers are designed to allow the cone to move freely using a suspension system.

As you carefully and lightly press on the cone, you should look out for the following signs:

• No movement: This could be an indication that the sub has blown.
• A wobbly cone:  If the cone staggers, its suspension system no longer serves its purpose as required.

3. Test the Voice Coil

A voice coil is attached to the subwoofer’s cone. It has positive and negative terminals and is designed to produce the motive force to the cone by the reaction of a magnetic field to the current passing through it.

If you want to test whether the coil is blown, use a multimeter. It measures impedance. If the coil has infinite impedance, then it is likely blown. To obtain the impedance value, follow these steps:

1. Turn the subwoofer off
2. Unplug the power source
3. Remove all cables
4. Remove the sub from its enclosure
5. Attach the multimeter probes to the corresponding voice coil terminals
6. Turn on the multimeter
7. Read the result

You should expect one of these three different types of results.

• No resistance at all or infinite resistance: Voice coils are damaged
• Reading shifting abruptly: Voice coil completely damaged
• Resistance is above 1.0 ohm: Voice coil fully functional

Why Do Subwoofers Blow?

Here are the two main reasons subwoofers get blown:

1. Too Much Power Supply

Excessive power is the number one cause of subwoofer damage. When the amp suppliers too much power to the sub, it’s forced to operate beyond its limits. This can occur due to mismatched impedances for example. 

This creates unbearable pressure that ultimately results in damage.

Modern subs can handle more power than the indicated room mean square (RMS), also known as continuous power handling. Nonetheless, it would be best if you still did due diligence.

As you listen to your music, you need to ensure the sound is clear.

2. Distorted Signal

When the sub receives too little power, it overheats and creates distorted signals. This can cause the subwoofer to stop working while the amp has power. 

In a bid to improve sound quality, many people turn up the volume when they hear distorted signals, which only helps create sustained clipping or a crackling sound as the volume changes.

The fact that it’s often difficult to identify a distorted signal early enough which complicates the matter further.  

You can minimize the risk of damage by learning to identify a clipping subwoofer fast. When you realize your sub suddenly sounds extremely odd and loud, it could be clipping. The subwoofer won’t be able to play bass notes.

The best way to prevent a sustained clipping is to use an amp rated for your subwoofer’s RMS.

Can You Fix a Blown Subwoofer?

In some cases, you can fix your blown subwoofer without worrying about hiring a technician.

Another quick option is to check whether your warranty is valid and go for a replacement. 

If you choose to fix your blown sub alone, here is what you can do to fix different issues by using things around the house:

Stuck Voice Coil

If your voice coil is stuck, look for a flashlight or a similar round object and use it to push the coil back into place. After that, test whether it works.

Tear

To repair a tear, you could use a paper towel and speaker dust cap glue. Apply your glue to the towel and use it to cover the hole. The paper towel should be smooth to ensure a seamless patch job.

Foam Surround

You can repair a broken foam surround by separating the gasket from the frame and then cutting the damaged part off the sub. Use rubbing alcohol to do away with the residue, and then install the new foam surround.

Fit the new foam surround and give time for the glue to set. Lastly, reinstall the gasket.

Subwoofer Cone and Coil

Remove the coil and then cut out the spider. Next, remove the voice coils and the gasket, and then clean any debris. After that, remove solder and wires. Ensure the new coil lines up with the terminals.

Glue the spider back to its original position. Subsequently, apply glue where the gasket sat, put the speaker cone into the correct position, and place the lead-out wires flat against the cone.

Solder the lead wires, then thread them. Place the dust and cone cover back on and solder the lead wires in the basket terminals.

Lastly, replace the driver and test it.

What Does A Blown Subwoofer Sound Like?

To diagnose a blown sub, check if the sound quality worsens as you increase the volume. The higher the volume, the more distorted the sound becomes and the sub begins to crackle instead of producing a clear sound.

What Happens When A Subwoofer Blows?

When a subwoofer blows, it begins to crackle and pop and produces a distorted sound. This is usually caused by the audio signal overpowering the speaker’s amplifier. When the signal transmitted to the amp is too powerful, it results in a blown subwoofer.

How Do I Stop My Subwoofer From Blowing?

You can prevent a blown sub by isolating the subwoofer and reducing the noise interference around it. That way, the volume does not have to be turned up so high that it overloads the sub’s amp and causes it to blow.

Wrapping Up

If you suspect your subwoofer is blown off, start by diagnosing the exact type of damage using the three methods we’ve discussed. You can also use the tips to fix it. Alternatively, you can hire an expert to repair the device It would also be best to consider buying a new amp with the right power and impedance rating to protect your subwoofers in the future.