Carefully remove the rubber cover (glued) from the base.

Remove the 3 screws using a screwdriver.

Pull the lower part carefully to open the casing.

You may use a slotted screwdriver, plastic card etc. along the slit to open as the cables are fixed with sealing paste inside.

When the slit opened, remove

the red battery cable plug and the white speaker cable plug (red arrows) from the socket by pulling and

the volume/play control cable by pulling the black lash (green arrow) upward and pulling the cable out of the socket

to separate the lower (PCB) part from the speaker & battery part.