A tip for anyone else attempting something similar would be to use a Multitool like this http://www.argos.co.uk/product/7967397 With a new blade they are surprisingly good for cutting square holes in wood or particle board. Alternatively a Rotozip would do the job although I find it difficult to get straight lines with one.
Great info for the rest of us, thanks for doing this! Since it has burned/snapped voice coil, not just bad solder, it was doomed anyway Extra fake grille is priceless!!!!! What is the value of its capacitor?
Yeah that cap is a pretty typical "crossover" for a boombox. The Telefunken Studio 1 is the only boombox I've seen with a legitimate crossover network. Although perhaps the Pioneer CK and Sony FH models have them too
