After you have the diagram, construct the product on the assembly station.
The Boombox (Diagram) can be obtained for free by giving 5 Data Discs to Petra during Mission: Panbat Infestation. The Boombox and the Loudspeaker can be taken simultaneously by providing 8 Data Disks altogether. However, if only the Boombox is taken, the other diagram is given at the end of the year through the mail.
Boombox (Diagram) can be used to learn how to make Boomboxes.
8 Bronze Plate
1 Cassette Box
2 Leather Horn
2 Copper Coil
2 Small Silicon Chip