Floor boxes are typically used on stages in auditoriums for various connections (mic, speaker cables, etc.) and occasionally in office settings for recessed power. There’s no reason why it wouldn’t work in a residential setting for speaker wire. Often the company selling them will let you custom order what connections you want under the door. Probably unusual for them to do binding posts, but if not I’m sure they could do 1/4" or Speakon jacks.
Regards,
Wayne A. Pflughaupt