Diagnosis
Dynamic range compression is off. This is common with movie audio tracks. The JBL 'Night Mode' or 'Voice Enhance' features are designed to fix this.
How to Fix It
Press the 'Sound' button on the remote repeatedly to cycle through modes. Stop on 'NIGHT' mode. This compresses the dynamic range, boosting quiet dialogue and limiting loud effects. Alternatively, use 'VOICE' mode for dialogue clarity.
If That Didn't Work
Run the JBL One Spatial Calibration again. Use the remote. This tunes the soundbar to your room's acoustics, which can significantly improve vocal frequency response. Do it in your normal listening position.
Heads Up
Using 'Night Mode' or 'Voice Enhance' will reduce the overall impact and width of the Dolby Atmos effect. It's a trade-off for clarity.