What Does This Error Mean?

JBL stereo balance off with one side louder is usually caused by the phone or device audio balance setting being off-center. Go to phone Settings > Accessibility > Audio Balance and center the slider, then test the JBL again.

Affected Models

JBL stereo speaker pairs
JBL Charge 5 in stereo mode
JBL Flip 6 stereo pair
JBL wireless headphones
JBL Connect+ paired speakers

Common Causes

Phone or tablet audio balance setting shifted away from center in Accessibility settings
One JBL speaker in a stereo pair at different volume from the other — volumes not matched
Bluetooth stereo pairing (Connect+, PartyBoost) not synchronizing volume between both units
One channel of the JBL hardware driver or passive radiator has failed
Audio source file itself has an uneven channel balance

How to Fix It

Check the phone audio balance setting.

On iPhone: go to Settings > Accessibility > Audio/Visual and check the Balance slider — it should be centered. On Android: go to Settings > Accessibility > Hearing > Audio Balance or Mono Audio. A balance shifted even slightly causes one side of a stereo output to sound louder.
Match the volume on both JBL speakers in a stereo pair.

When two JBL speakers are paired in stereo mode, each speaker maintains its own volume level. Adjust both speakers to the same volume using their individual volume buttons. A difference of even a few steps in volume creates a noticeable balance imbalance.
Reset the stereo pairing.

Disconnect both JBL speakers from the stereo pair by holding the Connect or PartyBoost button on each. Power cycle both speakers. Re-establish the stereo pair from scratch using the Connect or PartyBoost button on both units. A fresh pair synchronizes volume levels and channel assignments.
Test with a known balanced audio track.

Play a mono audio source (a voice recording or a mono test tone) to check whether the balance issue is in the speaker or the audio source. If a mono source sounds centered, the original audio source had an unequal channel balance rather than the JBL.
Check equalizer settings in the JBL Portable app.

Open the JBL Portable app and go to the equalizer section. Ensure no custom EQ preset is boosting or cutting frequencies only on one channel. Reset the equalizer to Flat or Default and retest the balance.

When to Call a Professional

If the balance issue only affects the JBL and the phone balance is centered, and the imbalance persists with all audio sources, one driver (speaker element) inside the JBL may have failed. Contact JBL support.