Key takeaways

• Perform the subwoofer hum test by isolating the subwoofer. This will help you identify if it’s faulty!
• If your subwoofer is humming a near G or B-Flat pitch, pay attention to the proximity of the power cord and subwoofer cable.
• Connect your subwoofer and amplifier to the same electrical isolation power socket extension hub.
• Use the infinity method when coiling excessive cable runs to reduce cable-induced electronic noise.
• Being methodical when connecting your electronics is the only way to identify if another source is causing your subwoofer to hum.

Why does my subwoofer hum?

1. The subwoofer itself is causing the hum

This is the one that everyone blames first, but in reality, most subwoofers are very robust, and it’s usually other components that cause the hum. However, we can’t ignore factors such as the age of your subwoofer, which could also be responsible for the noise.

Yes, components can fail at any age, but it’s more likely to happen as they get older or if a power surge affects one of their critical parts.

Why this happens is down to the sensitivity of some of these internal components, which require AC-to-DC conversion to work. Microprocessors, capacitors, resistors, and other circuitry can be damaged if this conversion isn’t working as intended, potentially causing components to overheat and fail.

The subwoofer hum test is simple, as shown in the “how to fix” section below. If the test indicates an issue with your subwoofer, you’ll need to contact the support team for a fix.

How to fix

The subwoofer hum test is simple. Power down the subwoofer and unplug everything except the mains cable. Then, turn the subwoofer back on. If you can still hear a hum, contact the brand’s support team.

2. Power cord interference

No, this isn’t a myth, and depending on your geographical location, it can affect you at different frequencies. Most electrical systems operate at either 50Hz or 60Hz, with harmonic hum occurring at 100Hz or 120Hz, and so on.

These hums also create a near-musical pitch, with 50Hz being close to a G and 60Hz close to a B-flat.

So, what’s happening? Essentially, a power cord may be too close to the subwoofer cable. With a gap of just 2.54cm, and depending on the shielding, the subwoofer cable can pick up electrical interference from the power cord. As above, the fix is fairly straightforward, although sometimes a more substantial change may be required due to cabling limitations.

How to fix

Create some distance between the power cords and cabling. Increasing the gap from 2.54cm to 10.16cm reduces the induced effect to around 6.25%, giving even poorly shielded cables a fighting chance.

Alternatively, it may be time to invest in a better mains cable with improved shielding.

3. Ground issues

This usually happens when your subwoofer is located in a different area of the room from your other electronics. Those who perform the subwoofer crawl may encounter this more often, while others may simply prefer not to have their subwoofer close to the rest of their equipment.

So, why can this create a subwoofer hum when everything you’ve read says you should perform the subwoofer crawl or that a subwoofer can be placed almost anywhere in a room?

The answer is simple, and it has more to do with your home and its plug sockets. Electrical equipment either needs to be earthed or use a double-insulation system. When you plug your equipment into different sockets, depending on how those sockets are connected at the consumer unit, you can create a ground loop. This can present itself as a subwoofer hum and may be either straightforward or a little more difficult to fix.

How to fix

Ideally, your subwoofer and amplifier should be plugged into the same ring mains to eliminate the ground-loop issue. This might mean using a long, well-insulated mains cable to reach the same gang of plug sockets or moving the subwoofer closer so both can use the same sockets. If that fails, you may need to purchase an RCA isolation transformer.

4. Poorly shielded cables

We mentioned the importance of using a shielded subwoofer cable, and one of the reasons is that a 75Ω subwoofer cable can essentially act like a TV aerial, picking up interference from the environment around it.

Its job is to send a signal from the source to the subwoofer, and depending on its length, shielding, or even a simple user error, you might find yourself hearing that dreaded subwoofer hum.

Long, poorly shielded subwoofer cables are more susceptible to interference, which is why better-quality 75Ω subwoofer cables are available. These use different materials and shielding methods to help minimise the problem.

You can also introduce subwoofer hum by coiling excess cable to hide it away and create a neater setup. Both of these issues are easily solved, and one of the solutions is completely free.

How to fix

If your subwoofer cable is picking up interference, it could be an issue covered in step two. However, if you’ve already addressed this area, the problem is most likely the subwoofer cable itself or the way you’ve coiled any excess cable.

The free fix is to uncoil the subwoofer cable and recoil it using an infinity loop, so the cable crosses itself at a 90° angle at the crossover point.

If you haven’t coiled any excess subwoofer cable, you may need to upgrade to a cable with better shielding.

5. Something has changed in your setup

This is going to be the hardest subwoofer hum to solve, as it generally requires more investigation. If your subwoofer has only recently started humming, look at anything you’ve recently added or changed in your setup.

If the setup is new, the process can be easy or difficult depending on how sophisticated your hi-fi or home cinema system is. For those with an HT bypass setup, there are added complications, particularly if you’re connecting a high-level subwoofer input to the integrated stereo amplifier and the LFE input to the AV receiver.

Another factor could be that some of your electronics don’t use an earth and instead employ a double-insulation system. The fixes for these issues are generally the same and can take time, as there’s rarely a quick solution.

How to fix

The quickest way to solve this system issue is to go right back to the start. Power down and unplug your system, then disconnect everything. Make sure none of your cables are coiled unless you’re using the infinity method, and try to keep mains cables and interconnects at least 2.54cm apart when reconnecting them.

Reconnect each device one at a time and test whether it is introducing the hum. If you reconnect every device without hearing a hum, it was most likely the way the system was originally wired that caused the issue.

If you identify a problem device, contact the brand’s support team, as it shouldn’t be introducing a hum into the system and could indicate a fault.

For an HT bypass system, ensure you’ve connected the high-level cable correctly using the latest method. This involves bypassing the traditional negative connection and finding a ground on the amplifier itself to isolate the negative signal.

FAQs

How do I stop my subwoofer from humming?

There are plenty of reasons why your subwoofer might hum, and our easy guide takes you through five simple steps to identify the cause and solve the problem.

Why is my subwoofer humming even though there is no input?

Your subwoofer humming, even though there’s no input, is either a ground-loop issue or something more serious, such as a faulty sub. Let’s rule out the worst first by performing the subwoofer hum test: isolate the subwoofer with only the power cable connected. If it still hums, it could be faulty. For everything else, follow steps two to five.

What are the signs of a blown subwoofer?

A subwoofer hum can indicate a repairable fault in most cases, while rattling, distorted sound, or banging and popping during playback could mean that something more serious is wrong with your subwoofer. In these cases, you’ll need to contact the brand’s support team.

Final thoughts

Our guide to subwoofer hum may have surprised you! There’s a range of reasons why a sub might make that annoying noise, but hopefully our solutions can help you remove or reduce the hum to an inaudible level.

Many of the solutions are free, while others may require you to change cables or, in more difficult cases, purchase an RCA isolation transformer. Either way, there are plenty of things you can try to successfully reduce or eliminate your subwoofer hum.