The meanie in me want's to say RTFM!!!

Honestly...Don't stop asking questions. even the stupid ones. I guaranty we've asked them too and I'll keep asking them.

Here's a digital copy of the F6B owners manual and my link starts with the Audio controls page. The Audio button turns the system ON and OFF and switches between headset and speaker outputs. Pushing the MODE knob allows for Treble, Bass, and other sound system changes.