Go into Settings -> "Sounds and vibration" -> "Advanced sound settings" -> "Sound quality and effects"
Then you can visit "Adapt sound" and Equalizer to adjust the sound.
Ok soooooo I feel the same as you about the sound. So with Dolby atmos it was cool at first but then I got a JBL speaker and older versions of galaxy's sound way better. I have s10+
That's because they've removed the bass and treble dials.. see the picture attached. This was on my S8. And I noticed a difference in music when I upgraded to a S10+. I've raised this with them so many times.. still nothing.