Well, I can fix that.
Start by prying the recessed top panel off the case:
Remove the circuit board to expose the tiny speaker, taking care not to rip the tiny wires out of the tiny connector:
You can’t measure a dead speaker, but it seems to be an 8 Ω unit.
The speaker sits in a rubber surround, with a foam rubber cushion against the PCB, tucked into a walled garden stiffening the case:
I don’t happen to have a tiny 8 Ω speaker, but I do have a bunch of small speakers (Update: 28 mm OD), so I bulldozed those walls with a flush cutting pliers and a bit of cussing to make room:
Nibble an adapter ring to match the rim of the new speaker, thereby routing the sound out those little holes, and hot-melt glue it in place:
Hot-melt glue the new speaker in place atop the adapter, taking care to fill all the edges / cracks / crevices below it with an impenetrable wall of glop:
The sealing part turns out to be critical with these little speakers, because a leak from front to back will pretty much cancel all the sound from the cone.
Cut the wires off the old speaker, affix to the new one, replace the PCB, snap the case lid in place, and it sounds better than new.
Millions of transistors in those ICs, but Ooma can’t spec a good speaker? Maybe they should have used a bigger speaker to begin with; ya never know.