How to Tell if a Car Subwoofer is Blown

A blown subwoofer is one of the most common problems car audio enthusiasts face.

As it’s more common in used subwoofers, many car owners want to know if there’s a way they can identify a blown sub without purchasing it first.

The best way to do this is by listening to music through a subwoofer. A blown subwoofer will produce a muddy and distorted sound.

If listening is not possible, you can physically inspect or test it with a multimeter.

This post will discuss these tests and how you can fix blown subwoofers.

What is a Blown Subwoofer?

The ‘blown subwoofer’ is an umbrella term indicating that the subwoofer is not working correctly. There can be multiple reasons behind blown subwoofers, such as poor ventilation, overpowering, poor installation, or manufacturing defect.

If the sound was playing like usual in your vehicle and you’re suddenly getting distortion in the low-end frequencies, there are chances that the subwoofer is blown.

There are slim chances that a new subwoofer will be blown out of the box. That’s because premium brands don’t want to tarnish their reputation by selling you defective pieces. 

But the same can’t be said about second-hand subwoofers.

Let’s face it: most of us don’t have an extra $300-$400 budget for a new subwoofer.

Therefore, it feels reasonable to go for a used subwoofer as these used subs come at a discounted price. But at the same time, some fake sellers will try to rip you off by selling you a damaged subwoofer.

Therefore, you must do all the testing before buying a used sub.

How to Tell if A Subwoofer is Blown

Listen to music

Listening to music is the easiest way to test whether a subwoofer is blown.

Here’s what you need to do:

• Turn on your car radio and play some bass-heavy music.
• Keep the volume level at halfway initially.
• Then slowly increase the volume level and notice if you hear any difference in the bass response. A blown subwoofer will have a bass response weaker than usual. And it will sound different than the rest of the audio system.
• Apart from that, you’ll have to check for any noises in the sound. A muffed or distorted sound at the higher volume levels or rattling/buzzing noises at the bass-heavy section of the soundtrack indicates some issues with the voice coil, cone, or suspension of the subwoofer.

Use a Multimeter

If you’re meeting the seller in person for the first time, they might not have powered the sub at that time – meaning you can’t test it by listening to music.

In such a case, you’ll have to use a multimeter to measure the resistance in the subwoofer’s voice coil.

Here’s how you can do it:

• Set the multimeter to resistance mode.
• Connect its positive and negative leads to each other. You should get a 0.3-0.4 Ohm reading. Note it down.
• Then touch the positive cable to the positive speaker terminal of the subwoofer and the negative cable to the negative terminal.
• Ensure that the cone is facing the upward direction and not touching anything.
• You’ll again get a reading – depending on your subwoofer’s impedance. If you don’t get any value or get a 0L reading, it indicates that the internal circuit of the subwoofer is not working as the current is not passing through it.
• Subtract the earlier reading from this reading. For example, if you get 2.3 Ohm this time, the final resistance value will be 2.3-0.3=2.
• If the final resistance value matches the impedance of your subwoofer, then it’s working fine. Otherwise, it’s not.
• If you’re testing a dual-voice coil subwoofer, you’ll have to test the resistance for both coils individually. Both of the voice coils should give you the same reading.
• This point is important as some people mistakenly touch the multimeter leads to terminals of different voice coils (+ve to VC1 and -ve to VC2, or vice versa). And when they get a 0L reading, they think something’s wrong with the subwoofer.

Physical Inspection

Another way you can test the subwoofer is through physical inspection.

The first thing you need to check here is the surround. This is the foam that connects the speaker’s cone to the speaker basket. You need to make sure that this foam doesn’t have any cracks or holes. And that it bounces back up when you push it down with your thumb or fingers.

Similarly, you need to check the speaker cone and the dust cap. You can do that through the ‘push’ test. As its name implies, you need to push the cone with the help of your thumb/fingers evenly from all directions and examine its movement.

If the cone doesn’t move, it indicates that the voice coil inside is frozen. On the other hand, if the cone is moving, but you hear a scratching sound, it suggests that the voice coil is rubbing against the internal components (the subwoofer is blown).

In some other cases, the cone moves back and forth repeatedly upon pressing, which indicates that the speaker spider is damaged. For those who don’t know, the speaker spider is the component that controls the movement of the voice coil and speaker cone and also dissipates the heat produced by the former.

What Causes Subwoofers To Blow?

Overpowering

The overpowering is one of the most common reasons why subwoofers blow. Most car audio installers try to put as powerful an amp in their vehicles as possible – not realizing that their subwoofer comes with a specific range for power handling, also known as RMS power rating.

Supplying the subwoofer power beyond that range can cause the voice coil to burn out itself and other internal components.

Underpowering

In underpowering, we pair smaller, weaker amplifiers to the subwoofer.

It causes the amplifier to work beyond capacity, resulting in a clipped signal. This clipped signal, in turn, causes the subwoofer con to move back and forth in an abnormal sequence, putting extra stress on the cone, surround, and spider suspension.

This extra stress can result in permanent subwoofer damage in the long run.

How to fix a Blown Subwoofer

Repair The Subwoofer

If you’ve found problems with the subwoofer earlier, there is a high chance that the damage is not severe. In such a case, you only need to repair or replace that damaged component inside the speaker, such as the spider cone, surround, or voice coil.

Replace The Subwoofer

On the other hand, if you’ve found out about this problem late, the damage will be too extensive for any repair. At that point, it’s not worth fixing the subwoofer as most parts are damaged. In such situations, going for a new subwoofer is a better option.

You might be interested in finding:

• The 7 Best 12-Inch Subwoofers (2023 Updated Products)
• Top 5 Best Car Powered Subwoofer (2023 Updated Products)

Conclusion

A blown car subwoofer can negatively impact the quality of your vehicle’s audio system.

Following the steps above, you can quickly determine if your subwoofer is blown or if the issue is with some other components.

And how you can fix it if it’s actually blown.

Frequently Asked Questions