Volume maximizes when DS4 switches from TMJ Multiple Output Device back to default audio output
When opening or using DS4, if your system default audio becomes very loud and does not return to the default volume the please do the following/
1. On Mac Desktop Press: command + space – The follow should appear.
2. Type in field which appears “Audio Midi”. Audio midi
setup should then appear. Select and open it by
clicking on it. You will then see something like this. From
this list select the default output device on your computer. Select it
by clicking on it. Next adjust the channel volume by moving the sliders
to the left and decreasing volume and then close and save these new
settings. 
If
you do this and you still hear your volume being reset, please
uninstall and reinstall it and then try this procedure again. Please
close DS and uninstall it by going to your Applications folder and
right clicking the SS icon and select "Send to Trash". After that,
download from the link below, reinstall, and then try again.
If this does not solve your problem please complete a support ticket.