Hello LibueStrebel
When I install a new projector in a classroom at our school, it is always something of the first to turn off the speaker. I don't think any beamer has speakers sufficient for a classroom. We have installed a small hi-fi system in each of our 50 or so rooms with speakers hung next to the screens. If necessary, active speakers that you can connect directly to the computer will also do. Projector loudspeakers (including those of the TH683) are really only suitable for extreme emergencies.