If sound plays in only one earcup on the Ace, work from the connection and settings, since the two cups share one Bluetooth link. Update the headphones in the app, reconnect by forgetting and re-pairing, and force reboot with a 10-second hold and USB-C disconnected. Check the source: play the same track on another device and through the phone speaker to see if the source is mono, and compare a stereo track from another app.
Check wear detection in the app, which changes behavior when a cup is lifted, and Noise Control: Aware Mode and Noise Canceling can change the perceived balance if one earcup is not sealed, so re-seat both cups and enable Adaptive Cancellation. Reset EQ to neutral, since extreme EQ can make one side seem weak. For TV, Sonos's TV Audio Swap gives a spatial or virtualised mix, and Dynamic Head Tracking shifts the center point; disable head tracking to compare. If one side stays silent with several sources after a reset, book service.
Differential
Likely causes of “Sonos Ace headphones plays from only one side or channel”, and how to tell them apart
- 1
A mono or one-sided source
What separates it Only one side plays in one app because the source is mono or one sided
How to confirm Test another app and another device, to see whether the fault follows the source
- 2
A poor seal on one earcup
What separates it One side sounds weak because one ear cup has a poor seal
How to confirm Re seat the ear cup, and enable Adaptive Cancellation, then listen again
- 3
Extreme EQ
What separates it One frequency dominates the sound because the EQ is set to an extreme
How to confirm Reset the EQ to neutral, and listen again
- 4
Head tracking center is off
What separates it The TV audio seems to lean because the head tracking center is off
How to confirm Reset the center by toggling Dynamic Head Tracking off and on
- 5
A hardware fault
What separates it One ear cup is silent everywhere, which points to a hardware fault
How to confirm Book a service with Sonos, since a silent ear cup needs a repair
- 6
Spatial audio for TV is on
What separates it Stereo content sounds virtualised and uneven because spatial audio for TV is on
How to confirm Turn Spatial Audio off in the Home Theater settings to compare
- 7
A source app applies its own balance
What separates it One side is lower in one app only because that source app applies its own balance
How to confirm Reset the app's balance and test another app
Before you touch a setting
Record this first — changing settings destroys the evidence
- Which side is weak or silent and on what sources
- Whether it follows the headphones across devices
- The EQ, Noise Control and head tracking settings
Try in this order
0 of 7 completedTest another source
ReversibleTest another source, by playing the same track from another app and another device, and then test again to see whether it helped.
Re-seat
ReversibleRe seat the ear cups, and check the seal around each ear, and then test again to see whether it helped.
Reset EQ
ReversibleReset the EQ, by setting all of the sliders to neutral in the app, and then test again to see whether it helped.
Toggle head tracking
ReversibleToggle head tracking, by turning it off and then on again, and then test again to see whether it helped.
Contact Sonos
ReversibleContact Sonos Support if one side stays silent, giving them the model, and then test again to see whether it helped.
Compare with spatial audio off
ReversibleCompare with spatial audio off, by turning Spatial Audio off under Home Theater settings, and listening again.
Test a second pair
ReversibleTest a second pair, by playing the same source on another headset, to separate the source from the headphones.
Model-specific
What is true of this model and not of its siblings
- Head tracking
- Sonos says Dynamic Head Tracking assigns the audio's center point in front of where you face and can be reset by toggling it.
- Fit
- Adaptive Cancellation improves ANC when the headphones do not fit perfectly.
- Where to look
- Sonos keeps the Ace's Noise Control, EQ, head tracking and TV Audio Swap settings in the Sonos app under Settings, the headphones.
Stop boundary
When this stops being a self-service repair
- !If one earcup is silent on every source after a reset, contact Sonos Support
- !If it follows one app, contact that app
- !If it is TV only, check TV Audio Swap
Evidence ledger
Sources behind this answer
Adaptive Cancellation and seals.
Spatial audio and Dynamic Head Tracking.
Resetting the Ace.
Updating.
The company and its products.
Exact questions
Common questions
Why is one side of my Sonos Ace quieter?+
A poor seal, EQ or a mono source; test another source.
Can head tracking cause it?+
It shifts the center point; toggle it to compare.
Does ANC cause it?+
A poor seal reduces ANC on one side.
Should I reset?+
Reboot and re pair first, and reset the headphones only if that does not help.
Is it the app or the headphones?+
Test on another app and device.
Does the Ace Ultra behave differently?+
The Ace Ultra can behave differently, and Sonos's articles cover both models.
Can I test my hearing?+
Compare with another pair of headphones.
Should I contact Sonos?+
If it is silent on every source after a reset.