How does the size of a speaker box change the sound it produces at different frequencies? You build three sealed plywood enclosures with depths of 500 mm, 400 mm, and 300 mm. Each one holds the same 8-inch speaker. You play test tones at 30 Hz, 50 Hz, 80 Hz, 150 Hz, 300 Hz, and 600 Hz through each enclosure. A decibel meter placed one meter away records the volume at each frequency. The data shows whether smaller boxes boost certain frequencies above the baseline level that larger boxes keep flat.