Sound preference pane will not open in El Capitan My 2.7gHz core i7 mac mini running 10.11.6 will not open the Sound Preferences pane. Since upgrading to Yosemite I have had sound preferences problems.  I produce audio using Logic X and an Apogee ONE audio interface.
The only thing that works on my Mac with this problem is running in the console the following command:

sudo killall coreaudiod