Two photos from a speaker manufacturer in Dongguan. These constitute basically the entirety of what I know about speaker manufacturing.

From the supplier's email: "It is our time 17:18, samples materials has arrived and started production, please check attachment photo."

From the supplier's email: "now at the stage of assembling voice coil, waiting for glue to dry, then assembling dust cap, please check attachment photo."

So, there you go. Speakers. I'm looking to learn more: ping me if you can help (seriously).