One side of your Sonos Ace is silent. Whether it's the left, the right, or a driver that drops out during a song while the other keeps playing, the cause is almost always something that takes five minutes to sort out. Hardware failure is rare. What looks like a dead driver is usually a power issue, a connection hiccup, or a settings problem specific to these over-ear headphones.
Before doing anything else, turn the headphones off and on again. Hold the Power/Bluetooth button for about two seconds to power them down, then press it again to turn them back on. If the silent side comes back, you saved yourself a lot of time. If not, keep reading.
Check Your Device's Audio Balance
Before assuming the driver is dead, check your phone or computer's audio balance. A slider that has drifted off-center sends all the audio to one side regardless of which headphone driver you're using. On an iPhone, open Settings > Accessibility > Audio & Visual and confirm the L/R balance slider is centered. On Android, that's Settings > Accessibility > Hearing enhancements or Audio balance. On a Mac, check System Settings > Sound > Output and make sure the balance isn't skewed. This check takes about 30 seconds and frequently saves the rest of the troubleshooting.
Clean the Charging Port and Contacts
The most common reason one side of an over-ear headphone stops working is that it isn't getting power properly. The Sonos Ace charges via USB-C, and that port can collect lint, dust, and pocket debris over time. A dirty or partially blocked USB-C port can interrupt charging for the whole unit, and in some cases cause one driver to behave erratically.
Take a close look at the USB-C port on the left earcup. Use a dry wooden toothpick or a plastic SIM eject tool to gently dislodge any visible debris. Do not use a metal tool. A can of compressed air aimed at the port can also clear out fine dust. Once the port is clean, plug the included USB-C cable into a 5W charger and let the headphones charge for at least 15 minutes before testing both sides.
Check the Sonos App for Per-Channel Settings
The Sonos app controls a lot of what the Ace does, including audio routing in specific modes. Open the Sonos app on your phone, tap the Sonos Ace card at the top, and look for any volume or channel adjustments. While there isn't a dedicated L/R balance slider in the app, the app does manage headphone settings like head detection and TV Audio Swap that can affect which driver is active.
If you've recently used TV Audio Swap with a Sonos soundbar, make sure the headphones have fully exited that mode. In the app, tap TV Audio Swap and confirm it shows "Disconnected" or "Not in use." A stuck swap session can keep one driver playing the soundbar feed while the other goes silent.
Re-Pair the Headphones Via the Sonos App
If only one driver works when you put the headphones on, the saved Bluetooth connection on your phone might be corrupt. Open Settings > Bluetooth on your phone, find Sonos Ace in the list, tap the info icon, and choose Forget This Device on iPhone or Unpair on Android.
Now open the Sonos app. Tap the gear icon, then Add Product and follow the on-screen prompts. The app will guide you through pairing the headphones fresh. This clears any pairing mismatch between the two drivers and usually resolves the silent-side issue when it's a connection fault rather than a hardware problem.
Factory Reset the Headphones
If cleaning and re-pairing didn't help, a factory reset is the next step. The Sonos Ace reset method is specific: hold the Power/Bluetooth button on the left earcup while plugging the USB-C cable into a power source. Keep holding the button as you plug it in. The LED indicator will flash, and the headphones will reset. Release the button once the reset completes.
This clears all internal settings, including any stuck audio routing that might be sending signal to only one driver. After the reset, you'll need to re-pair the headphones with your phone through the Sonos app. Take both earcups off, put the headphones on, and make sure audio is playing before assuming the fix worked.
Update the Firmware
Sonos has pushed multiple firmware updates for the Ace since its 2024 release, and some have addressed driver-related bugs. Outdated firmware can cause a range of audio issues, including one side going silent unexpectedly. To check, open the Sonos app, tap the Sonos Ace card, then tap System > Software Update. Install whatever is available.
The headphones need to be connected to your phone via Bluetooth during the update, and they should have at least 50% battery. The update takes about 10 minutes. After it finishes, test both sides. If the silent driver wakes up, a firmware bug was the culprit.
Test on a Different Device
If one driver is still silent after all the above, pair the Sonos Ace to a different phone or a computer. If both sides work fine on the second device, the issue is with the original phone's Bluetooth stack, not the headphones. Reset network settings on that phone or check if a recent system update created the problem.
If the same side is silent on every device you try, the driver itself is likely faulty. The Sonos Ace carries a one-year warranty from purchase. Contact Sonos support through the app for a replacement. Hardware failure on the Ace is uncommon, but it does happen, and Sonos handles it under warranty without much hassle.
If You're Using TV Audio Swap
The TV Audio Swap feature is one of the Sonos Ace's signature capabilities, but it only works with the Sonos Arc, Beam Gen 2, or Ray soundbars. If you're trying to use TV Audio Swap with an older Sonos soundbar or a third-party soundbar, the feature simply won't activate, and you might experience audio issues as the headphones try and fail to connect. Check your soundbar model in the Sonos app. If it's not supported, stick to standard Bluetooth audio for TV watching.
Double-Check the Source Track
Spatial Audio with Dolby Atmos works on the Ace only with specific tracks on Apple Music and Tidal. If you're playing a song that isn't mixed in Atmos, the headphones will output standard stereo. That's normal behavior, not a sign of a broken driver. Compare the audio between a known stereo track and an Atmos track to confirm the headphones are working correctly. If both sides play in all modes, your headphones are fine. The issue was just the source material.