DIAGNOSIS
The dynamic range of the source audio is too wide for your listening environment. The soundbar's default settings may not be optimizing for dialogue clarity.
FIX
1. Enable 'Voice Enhance' mode. Press the 'Voice Enhance' button on the remote (icon of a person speaking). The soundbar display will show 'VOICE ENHANCE ON'.
2. Adjust the center channel level. In the SmartThings app, go to Device Settings -> Soundbar -> Expert Settings -> Center Level. Increase it by +2 to +4.
3. Set the soundbar to 'Adaptive Sound' mode. This mode actively analyzes content and boosts dialogue frequencies.
IF THAT DIDN'T WORK
Check your source settings. Many streaming apps and Blu-ray players have a separate 'Dialogue Boost' or 'Dynamic Range Compression' setting. Enable it there as well.
HEADS UP
Do not simply raise the overall volume. This exacerbates the loud sound effects. The goal is to use processing to compress the dynamic range, making quiet sounds louder and loud sounds quieter relative to each other.