We can all agree that no matter what genre of music you’re listening to, a subwoofer makes a lot of difference. Custom audio setups have been a thing for decades and are a simple way of turning any location into a party, as long as the neighbors don’t mind.
However, if the subwoofer isn’t working, you’ve got to start looking for the cause. The amp signals that it’s working, but we can’t rule it out just yet. Whenever you’re facing an electrical problem, it’s important to start at the bottom and rule out every cause, no matter how simple it may seem. In this guide, I’ll clue you in on how some components can appear to be working but are in fact broken.
For quick reference, these are the likely causes of a malfunctioning subwoofer: loss of power, bad fuses, low voltage, incorrect impedance, bad amplifier, and a bad subwoofer.
The only tool you’ll need to properly identify problems with the subwoofer is a multimeter. You can use it to check fuses more quickly, but more importantly for accurately measuring voltage and impedance.
Whether you’re running stock or a newly installed subwoofer, the ground is always the first thing you should check, both for the subwoofer and amplifier.
Lack of ground will cause the subwoofer to create a hissing or humming noise, but more importantly, it can damage the sub and the amp.
To determine whether the connection has been grounded, first disconnect the ground terminal of the battery. Set the multimeter to the Ω setting and touch the two test leads to check their resistance. Any reading should be subtracted from further measurements for better accuracy.
Place the ground lead into the disconnected ground wire at the battery. You might need extension lead cables to reach the back of the vehicle as that’s where the amp and the subwoofer are located.
Use the live lead to probe the metal points where your amp and subwoofer are grounded. If you’ve used the base of the seat belt buckle or a cargo strap anchor, you may get a high reading. Your ground needs to read as low as possible. We’ve also covered grounding issues in this article, so take a look if you need additional information.
The fusebox is typically located underneath the hood or behind a cover next to the steering wheel. You’ve probably checked the fuses already, but merely looking at them from the top isn’t enough to properly identify whether a fuse is bad or not. You can pull out each of the fuses individually and check if the metal wire running through them has snapped, or use a multimeter to make the process faster.
To set up the multimeter, connect the black wire to the COM setting, as that is your ground. The red wire is live and it goes into the other slot of the multimeter, with markings like V, mA, or Ω (Ohm) on it. Set the dial to the lowest Ω setting, or in the case of the multimeter I’ve linked, just set it to Ω and it will auto adjust.
Place the two test leads on either side of the fuse so they touch the exposed metal. If the multimeter gives you a reading, it means the fuse is working. When there’s no reading, pull out the fuse and replace it with a new one. The following kit is something every car owner should have in their trunk, and it includes a fuse extractor to make it easier to pull out fuses without damaging them.
You may not be aware of this, but on the back of the amplifier, there’s usually a couple of fuses. Make sure to check them as they could be causing sound problems.
If you’re still not sure you’ve got the whole measuring process figured out, check out the following video that’ll take you through the process in more detail.
The amplifier and subwoofer require a specific amount of voltage to function properly. For the subwoofer, it’s the standard 12 volts that are delivered directly from the battery, while the amp needs 10.5 – 16.5 volts. Some amplifiers are regulated, meaning the difference in voltage will not affect the power, while voltage fluctuation directly affects the sound power in unregulated amp setups.
You might have incorrectly determined that the amplifier is working based on the signal light is on, but the light can turn on even if the voltage is much lower than necessary. To measure the voltage, you need to turn on the stereo and play a continuous sound of a single frequency to keep the voltage consistent. You can connect your phone and play something like this.
Set the multimeter to V (voltage) setting and check the reading on the battery by using the red lead on the live terminal and black lead on the ground. Write down the reading for future reference. Now, measure across the amplifier terminals to see how much voltage it actually receives.
A voltage difference between the battery and the terminal greater than 0.5V is a cause for concern, but anything less is tolerable. You can repeat the same test for the subwoofer and see if it receives the 12 volts it needs to function properly.
If you have a voltage drop, you’ll have to identify where the power drop is happening. This is usually caused by the power wire running to the amp or subwoofer, but the following video will do a great job of explaining this part of the process.
When something looks obvious, we tend to forget to read the instructions and just get to work, just remember the last time you got furniture from Ikea. The same goes for connecting the speaker to the amplifier – there’s left, there’s right, positive and negative, it all so simple, right? Well, not quite.
The things are straightforward if you’re dealing with a 4 channel system with 4 speakers. The top row of speaker outputs is for the front speakers, the bottom row is for the rear speakers, left & right, positive & negative are clearly marked. However, when you’re adding a subwoofer to the mix, you need to create a bridged connection.
For a setup with two speakers and one subwoofer, you bridge the bottom row outputs by using the positive of the left side, and the negative of the right side to connect the subwoofer. The speakers are connected to the top row, one on each side. A setup with four speakers and one subwoofer involves the same bridge at the bottom, but now you pair left side speakers and connect them two at the time, and do the same for the right side.
Finding the manual for your amp online is a very quick process, and making use of it can save you from having sound issues or even overloading the amp. The following video will give you a better idea of how to properly wire your speakers and subwoofers.
It’s possible that your stereo head unit isn’t set up to deliver any sound to the subwoofer. Check the manual and play with the settings until you can safely say it’s all set up properly. We’ve covered speaker-related issues in great detail in this article, so make sure to check it out.
If you’ve reached this point of the guide without finding a solution, it’s time to consider that either the amplifier or the subwoofer is not working.
Even if the amp worked fine before, incorrectly installing the subwoofer could have overloaded the amp and caused a failure. It’s also possible that the subwoofer arrived with a factory defect and has to be replaced.
For a subwoofer to function properly, it needs the right amount of air volume within its case. You cannot cramp a massive woofer into a small housing just because it fits – it needs a lot more air volume to work with. You can easily find this information on the subwoofer specification sheet, and see if it fits your intended mounting area.
Subwoofers can be divided into single, or double voice-coil designs. Voice coils represent the connection ports, and if your subwoofer has two of them, you have to connect both. The single voice coil setup is less complicated, but dual setups give you more versatility when installing several subwoofers and matching the impedance of the amplifier.
When you’re buying a subwoofer, it’s important to pay attention to the RMS continuous power rating, not the maximum power rating. You need to match the RMS continuous power rating to your amplifier to ensure everything is compatible and working properly.
If you’re using multiple subwoofers of, for example, 4 subwoofers of 300W RMS power each, then the amplifier needs to deliver 1200W. Having an underpowered subwoofer is not a problem, it just means its maximum power will be bottlenecked by the amp.
To determine whether the subwoofer requires a vented or sealed box, you need to calculate the EBP (Efficiency Bandwidth Product). From the product specification sheet, take the Free Air Resonance (Fs) value and divide it by the Electrical “Q” (Qes) value.
A value close to or above 100 signifies that the subwoofer is better suited for a vented box, while a value close to or below 50 indicates that a sealed box is the better option. Between 50 and 100, you can go with either box. This is not a rule set in stone, but it will help you get the best performance out of the subwoofer.
Subwoofers can last for decades if maintained properly. The main factors that can reduce the lifespan of a subwoofer are physical damage and a short-circuit caused by water or other liquids. Not cleaning the subwoofer at all can also cause damage.
By using a multimeter, you can check the circuit between the two sides of the fuse. Without one, you can pull out the fuse and look through the plastic at the wire in the middle. In a good fuse, it’ll form an Ω shape and look clean. When the fuse goes bad, the connection will break, and you’ll see some heat-caused discoloration of the plastic and metal.
No, a subwoofer will not go bad from sitting, as long as it’s not exposed to bad conditions, especially moisture which can corrode wires and the circuit.
Like every other component, you can expect the subwoofer to wear out, but if it’s well maintained the deterioration will be so slow you might never have to replace the subwoofer.
A solid subwoofer option for your vehicle will set you back between $100 to $200. Beyond the $200 mark, you can buy complete kits with an enclosure and even an amplifier.
Subwoofer installation costs around $100 in labor. If you add an amplifier and make the setup more complex, the price can quickly double.
Troubleshooting subwoofer problems is a process that requires patience and concentration. Work slowly, check every fuse, measure the ground resistance twice to confirm it’s good, and work your way through the list. If you’ve followed all the steps of this guide and still haven’t found the solution, then consider asking a professional electrician or car stereo company for assistance.
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