Have you ever put your phone into a plastic cup to amplify the sound? This is like that but something fun for the Scouts to pull together.
You'll need 2 plastic (or paper) cups, a cardboard tube and scissors (duct tape optional).
Wrap the tube in duct tape if desired.
Using the phone as a guide cut out a hole in the tube just big enough for your device.
Next, make a hole near the base of the cups just big enough for one end of the tube.
Repeat with the other cup
Turn the device volume up, put in the tube and rock on
pictures here - http://fortheboys.squarespace.com/home/2014/6/12/theme-week-diy-speakers.html