I'm using Boom2 ver. 1.4 on a 2011 MacBookAir running OSX El Capitan ver. 10.11.3 (15D21). In other words, software wise, everything is up to date.
Most of the time, Boom is not boosting the volume at all, and the volume slider has no affect on the perceived audio output level. Once in awhile, it will work. I have not been able to find a pattern in when it does or doesn't work.
Any help would be greatly appreciated.