There is a difference in volume between the left and right sides, or the bass (low frequency) sound is insufficient.

• Test the headphones with different devices (phone, laptop, etc.).

• Try another app/source: Sometimes the audio source or app may have balance issues. 

• If the headphone plug is dirty, clean the plug using a dry cloth.
• Check if there are any foreign objects or dirt (such as ear wax or dust) attached to the portion [A] of the headphones. Since this portion produces the sound, foreign objects may cause decreased volumes or deterioration of sound quality.
  
  An image of the canal type headphones with the earbuds removed
  

NOTE:

• When a dirty foreign object is attached to portion [A], clean the headphones by blowing the foreign object away using an air blower.
• Refrain from using a sharp object such as the tip of a pen. It might cause additional damage.
• In cases when the headphones tend to easily slip off from the ears, replace the size of each earbud to one that sits snug in each ear to improve the fit of the headphones.
• Replace the earbuds or earpads if they have become damaged or deteriorated.

If you feel that the bass (low frequency) sound is low or there is a difference in volume levels between the left and right sides of the headphones, change the earbuds to another size that comfortably and snugly fit both ears.

• M-sized earbuds come attached to the headphones at the time of purchase.
• Try the earbud sizes in order from the larger sizes to the smaller sizes, and use the ones that feel more sealed. The best size earbuds may be different for left and right ear.
• Make sure that you are wearing the earbuds properly:
  • For WF-1000XM5, WF-1000XM4, and LinkBuds S, you can measure the air-tightness of the earbud tips using the Determines Optimal Earbud Tips function of the Sony | Headphones Connect app. For details, refer to the How to wear the headphones properly and select most suitable earbud tips article.
  • Using the WF-SP800N as an example of wearing method, when you insert the units into each ear, twist the earbud to secure the arc supporter into your ear grooves. For details, refer to refer to your model's Help Guide.
     
     

On your smartphone or computer, check if the audio balance is centered:

For Android:

• Go to Settings > Accessibility > Hearing > Audio balance.

For iPhone:

• Go to Settings > Accessibility > Audio/Visual > Balance.

For Windows (Windows 10/11):

• Go to Control Panel > Sound > Playback > Properties > Levels > Balance.

For macOS:

• Go to System Settings > Sound > Output > Balance.

1. Forget the device in your phone’s Bluetooth settings. How to delete the Bluetooth device information of your playback device.

2. Re-pair the Headphones: Refer to How to pair Bluetooth headphones with a Bluetooth source device

• Open the Sony | Sound Connect app.

• Disable any sound effects (e.g., EQ, surround sound) to see if they’re causing the issue.

1. Reset the headphones.

2. Initialize the headphones.