President Woodrow Wilson came to San Diego September 9, 1919, to plead for his League of Nations, arriving at the Santa Fe depot on a special train with a squadron of seaplanes flying overhead. He began speech at 5 pm in City Stadium (later renamed Balboa Stadium) in Balboa Park. The stadium had been built for the 1915 Panama-Pacific Exposition and with a seating capacity of 23,500, the largest of its kind on the West Coast. Wilson was in ill health and spoke from a glass-enclosed platform at the south end of the stadium. 50,000 crowded into the stadium and the temporary bleachers on the field. Wilson voice was amplified by a public address system recently developed by Magnavox, based on the invention of a loudspeaker in 1911 by Peter Jensen and Edwin Pridham. Pridham had come to San Diego to supervise the installation and Jansen was in the glass platform with Wilson. Rather than use a microphone, Wilson stood on a circle drawn near the front of the stage and spoke into two large horns suspended over his head that directed his voice to the microphone. The loudspeakers were hidden behind flags and bunting around the platform. Although a tube in the amplifier shorted and had to be replaced just before the speech, the system worked well during the hour-long speech. The audience could clearly hear Wilson's words, applauded and shouted their approval. Wilson's voice could be heard one mile from the stadium. The sound did not project clearly to the far north end and people moved to the field to get closer to the glass platform. Pridham later concluded that the large size of the glass-enclosed platform created an echo effect that made Wilson's voice sound hollow in some directions. Wilson later collapsed in Pueblo Colorado and returned to Washington DC where he suffered another stroke and remained incapacitated for 6 months.
Lewis, W. David, "Peter L. Jensen and the Amplification of Sound" in Carroll W. Pursell, Jr., ed. Technology in America: a History of Individuals and Ideas. 2nd ed. Cambridge, Mass.: MIT Press, 1990.
Shepherd, Gerald A. "When the President Spoke at Balboa Stadium," Journal of San Diego History 32, No. 2 (Spring, 1986), 92-101.