The 'Boom box' is made out of 3 disposable camera's (you can use more than 3). I used the charge circuit from one camera and the capacitors from all 3 camera's and put them in parallel. Then I added a switch between the battaries and the charge circuit, a switch on the charge circuit itself to start charging the capacitors, and a switch after the capacitors to release the charge in one go (but I cannot recommend this to anybody because the switch welds itself together and gets stuck in one position. you would have to chose an appropriate switch that can handle the power). The 'Boom box' generates more than 2kV (max voltage my multimeter could read) and around 10 amps of current (biggest fuse it could blow with the thing).
STL-files can be found here: https://www.thingiverse.com/thing:2980012