With the recent update, G920VVRU4DQL1, 12/27/2017, the sound equalizer no longer functions. you cannot access the advanced sound options through the setting menu or the equalizer setting in the Samsung Music App.
I checked my wife's phone and her's has the same issue.
No sound app allows the equalizer to work.
Is there a way to disable the app? sometimes when you disable an app it will
revert back to the original app before any updates?
I tried so many different things and nothing worked. the sound equalizer functioned the day before the update.
It seems like it was disabled in the latest update from Verizon. Maybe Verizon doesn't want us to use the equalizer.
I wish there was a way to revert to the previous software version.
Try a System Cache Wipe first.