But the question of volume fluctuation from commercials to the show is as old as the TV. I may upset you by not duplicating that discussion.
I'd see if there is an other than optical link out of the TV as well as ask Samsung to find a way to apply volume leveling to the optical port.
http://forums.audioholics.com/forums/threads/volume-leveling.21868/ kicks it around and in the receiver terms it's called Dynamic Compression (volume leveling.)
See if your soundbar has this.
Soundbar: Samsung HW-K450
TV: Samsung KS8000
Both purchased together Dec. 23rd 2016
Problem/question: my problem is that there are major volume fluctuations while watching TV between the shows I'm watching and the commercials. I currently have the sound bar hooked up with the optical audio cable directly from the TV to the sound bar. I have the TV speakers set to external/optical out and so the only sound I hear is from the sound bar. I guess the main question I have is that if you are using this particular sound bar, does it have no volume regulation functions built-in? I know the Samsung TV has a true volume function that regulates the TV speakers, but from what I'm reading it does not regulate the audio signal going out from the optical cable? Any help with this would be much appreciated, because based on the current fluctuations I am experiencing while watching regular TV, this sound bar is almost unusable while watching cable TV.