In this article, the authors describe steps on how to develop a high-impact activity in which students build, test, and improve their own "coffee can" speakers to observe firsthand how loudspeakers work to convert electrical energy to sound. The activity is appropriate for students in grades three to six and lends itself best to students accustomed to working in groups and who have already done some hands-on investigations with electricity, magnetism, and sound. This invistigation needs materials and suggests that science teachers will build their own coffee can speakers first before trying the activity to the students. The steps provided for teachers are the following: organize the students; make the speakers; test the coffee cans; improve the speakers; explain how they work; and assess the students. (Contains 2 resources and 2 online resources.)