I have speakers plugged into the sound card, and USB headphones. Let's say I'm watching YouTube, and I disconnect my headphones; Speakers are now the main output device on Windows, but the YouTube tab in Firefox is still outputting to the headphones that are no longer connected. To fix it, I have to refresh the page. This indicates that Firefox checks for the current Output device when loading the page, but doesn't check it afterwards.

Please fix this in the future builds.