There was a casualty of my laser+speaker Lissajous proof of concept: while exploring the limits of how far I could push a speaker, I went too far and burned one up. It was an unfortunate but expected part of playing with using components outside of their designed purposes. And now the dead speaker has one final role to play: as a dissection subject so we can see what’s inside. This is a irreversibly destructive process because speakers are not built to be disassembled and repaired. Once I plunged the blade into the speaker surround, I am committed.
Once the surround was cut, I could access and cut the suspension underneath. After they were both cut I could lift the cone. Several problems were immediately visible. The voice coil that should have been attached to the bottom of the cone has separated, leaving a ring of charred material and a single thin strand of magnet wire. Emphasis on single: there should have been two wires for the coil! Also, lifting the cone released a strong odor of burnt insulation.
Since that thin strand of magnet wire is our only connection to the voice coil carcass still buried within its narrow slot, the only thing to do is to tug on it (gently) to unwind the coil. As wires were pulled, they occasionally brought up flakes of burnt speaker with them. Eventually, enough of the obstacles were removed that the charred remains of the voice coil could be recovered. It’s a pretty sorry sight and a fitting company to the smell.
I originally had the ambition of creating my own voice coil actuator out of the damaged chassis, by winding magnet wire around a 3D-printed replacement cone. But that’s before I saw how narrow the slot was. I could not make anything to fit in that slot, so the re-purposing plan was abandoned. We’ll just keep the big chunk of magnet because magnets are always fun. (Keep away from credit cards, though.)
The magnet assembly was held on to the speaker chassis by four big rivet-like structures. A drill press was summoned to remove the bulk of the metal. It was novel to see metal shavings align themselves to the magnetic field.
After the majority of the rivet were removed, the chassis was placed in a vice and the magnet assembly was pried loose from the chassis.
This still left four protrusions to cut flush, and the tedious task of cleanup – the metal chips really wanted to stay with the magnet! But by the end of the night I have a hefty speaker magnet assembly.