This summer I worked with Dr. John Krupczak, assistant professor of engineering at Hope College. He is currently developing a course called Science and Technology of Everyday Life. The motivation behind the course is to educate the general public about the technology that surrounds us but so few of us understand. The course is taught in a highly visual and hands on context. To be suitable for non-science and non-engineering majors, difficult math is left out and focus is on how things work while explaining the underlying science. The class is currently being taught at Hope and includes a lab section where students explore some technological devices and even make some of their own. My work this summer involved helping to improve existing laboratory projects and design new ones.

A number of labs were worked on including a four-bit adder calculator, a buzzer, a telegraph machine and a magnetism lab. Eventually my focus was narrowed to the loudspeaker and designing a laboratory project in which students learn how a loudspeaker works by making their own.

I began by making a loudspeaker from an existing lab found in a physics teachers' magazine. The design had a 30 gauge copper wire coil attached to a construction paper cone and surround which was mounted on a ring stand. The ends of the coil were hooked up to a stereo and when a cap screw on top of a magnet was placed up into the coil sound from the speaker could be heard, barely. The design needed to be much louder and held together in a portable box so students could take them home and try the speakers on their own stereos.

The problem of volume was worked on first. I identified four factors that affect volume: cone size, box dimensions, coil weight and impedance, and the magnetic field of the permanent magnet. Research into literature and available speakers, making and testing many different cones and coils and modeling magnetic fields with the computer software ANSYS were all things I did to help decide on a final design. Things to consider the whole time were to keep the cost low and production process interesting and feasible. Taking everything into account I chose my final design to have a cone with 14cm diameter, a wire coil of 80 turns of 38-gauge wire wrapped in one layer around a 2.lcm diameter paper ring. The permanent magnet was a ring with ID 1.00"and OD 2.375" sandwiched between two washers ID 15/16" and OD 2.25". A ½" diameter fine thread cap screw came through the ring and was held in place by a washer ID 9/16" and OD 1.375". The position of the magnet and hardware created an air gap between opposite poles of the magnet that the coil could rest in. This assembly resulted in the best sound so all that was left was mounting the speaker in a box.

Because the speaker is a learning tool, the speaker box was left open for viewing the inside, having two square cardboard faces held together with wooden posts at each corner. To mount the heavy magnet and hardware a cardboard mailing tube was found that fit tightly around the magnet holding it securely, and was mounted on the inside of the back face. The speaker was made stereo compatible with a terminal block that a speaker wire could be hooked into.

Final steps included recording my work and design in a technical report, deciding on and ordering materials, and writing the lab procedure for the class. I made several pictures using CAD and inserted them into the procedure where necessary.