I found the speaker connection is the 5th pin from the right on both sides of the LCD ribbon connector. I had previously desoldered this from the torn ribbon cable.
I may still try to find the signals on the logic board somewhere for a more sturdy connection. Of course the speaker sounds even...
Making good progress on this one.
iPad LCD replacement for powerbook - also boosts the resolution to 800x600!
EDIT: More details of what's going on here....
I've 3d printed a bezel for the LCD to fit the original bezel:
Excuse the fingerprints, and the colour choice of filament. I need to...