In 1992 we still have both 5" Wall Speakers and 8" Wall Speakers along with Inside Remote Controls which used a wide variety of Wall or Ceiling mounted music speakers.
A nice feature of the IM5006 was that each Wall Speaker or Remote Control had a built-in microphone. This meant that if you used a ceiling mounted music speaker, the Intercom functions still work very well because you were speaking into the microphone on the Wall Remote, not shouting up to the ceiling speaker.