The invention that changed how we listen together
The Birth of the Great Voice
In a small Napa workshop, Peter L. Jensen and Edwin S. Pridham created the first practical moving-coil loudspeaker—giving one voice the power to reach thousands.
Peter L. Jensen and Edwin S. Pridham with their Magnavox loudspeaker
Napa transformed more than wine.
More than a century ago, two young engineers turned an electrical signal into a shared public experience.
On May 6, 1915, Peter Laurits Jensen and Edwin Stewart Pridham developed a practical, high-output moving-coil loudspeaker in Napa. Their invention projected speech and music far beyond the natural limits of the human voice. They called it the Magnavox—from the Latin magna vox, meaning “great voice.”
Earlier inventors had experimented with electrically driven sound. Jensen and Pridham’s breakthrough was making the principle powerful and reliable enough for large-scale public address.
The collaborators
Two minds. One great voice.
Peter L. Jensen
Born on Denmark’s island of Falster in 1886, Jensen entered the laboratory of Valdemar Poulsen—pioneer of magnetic recording and arc radio—as a teenager. After years of work with Poulsen, Jensen was sent to America in 1909 to support the development of the Poulsen Wireless Telephone and Telegraph Company. There he met electrical engineer Edwin S. Pridham. Jensen’s combination of intuition, showmanship, and commercial imagination became central to the Magnavox story.
At Magnavox, Jensen served as chief engineer and helped move the loudspeaker from experimental apparatus to a practical public-address and radio-reproduction system. With Pridham, he also developed a noise-neutralizing microphone that could reject surrounding engine noise, making speech intelligible from aircraft and other loud environments.
After leaving Magnavox, Jensen founded Jensen Radio Manufacturing Company in Chicago. Its loudspeakers became influential in broadcast receivers, high-fidelity systems, cinema equipment, public address, and later guitar amplifiers. During World War II he advised the U.S. War Production Board’s Radio and Radar Division. He later formed Jensen Industries to manufacture phonograph needles and other products.
- 1903–09Worked with Valdemar Poulsen on magnetic recording and arc-radio technology.
- 1911Co-founded Commercial Wireless and Development Company, the enterprise that became Magnavox.
- 1917Co-invented the noise-neutralizing “lip” microphone used in aviation and military communications.
- 1927Founded Jensen Radio Manufacturing Company and built a second enduring audio brand.
- 1955Named an honorary member of the Audio Engineering Society; later honored by Denmark’s Order of the Dannebrog.
Edwin S. Pridham
Born in Illinois in 1881 and raised in California, Pridham studied physics and electrical engineering at Stanford, graduating in 1909. He worked with Stanford alumnus Cyril Elwell on the Poulsen wireless transmitter before joining Jensen. His formal training, careful measurement, and practical engineering discipline balanced Jensen’s experimental drive.
Pridham was not simply the quieter half of the loudspeaker partnership. He co-developed the moving-coil telephone receiver that led to the Magnavox, helped engineer its public demonstrations, and shared the work on the anti-noise microphone. That device used two acoustic paths to oppose ambient noise while preserving the speaker’s voice—an early and consequential form of acoustic noise cancellation.
Pridham remained with Magnavox after Jensen’s 1925 departure, helping guide engineering as the company expanded from public-address equipment into radio, phonographs, communications, and military systems. The Stanford archive specifically connects his career with Magnavox research in Napa, anti-noise systems used by the military, and the company’s later Oakland operation.
- 1909Graduated from Stanford with an A.B. in physics and worked on early Poulsen wireless transmission.
- 1911Co-founded the Napa laboratory where the practical moving-coil loudspeaker emerged.
- 1913–14Co-patented the moving-coil telephone receiver that established the core transducer principle.
- 1915–19Engineered landmark public demonstrations and helped deploy Magnavox systems for vast outdoor audiences.
- Later careerContinued at Magnavox as it developed radio, phonograph, public-address, aviation, and military communications products.
The “Great Voice” of the Magnavox
From a wire in a magnetic field to sound across a city.
Their original goal was to improve radio and telephone reception. Working in the Napa laboratory they formed in 1911, Jensen and Pridham experimented with Poulsen’s arc-radio technology. A chain of practical modifications led somewhere much larger.
A moving conductor
A fine wire suspended in a magnetic field moved in response to electrical signals. Jensen and Pridham asked whether that movement could reproduce the complex vibrations of speech.
A diaphragm and matchstick
They enlarged the mechanism and connected its moving wire to a diaphragm with a wooden match. Substituted for a telephone earpiece, it produced speech with surprising force and clarity.
The gooseneck horn
After thicker conductors and a copper-wire coil produced a stronger receiver—but little commercial interest—they attached a large gooseneck horn from an Edison phonograph. The horn efficiently coupled the diaphragm’s movement to the air and projected sound outward.
The first field tests
Pridham spoke inside the bungalow while a roof-mounted horn carried his voice across Napa. Jensen recalled intelligible speech at roughly a mile—and, under favorable conditions, much farther.
“Hello, Sacramento. Can you hear me?”Pridham’s remembered test message, projected from Napa’s “Cup and Saucer” hill
The great voice goes public
A remarkable year in sound
The loudspeaker is invented in Napa
Peter L. Jensen and Edwin S. Pridham completed their practical moving-coil loudspeaker at the F Street residence in Napa—creating the powerful “great voice” that would become the Magnavox.
The first documented song in Napa
During the summer of 1915, Jensen and Pridham played Ernestine Schumann-Heink’s recording of “Heilige Nacht”—“Silent Night”—through their experimental system. Jensen’s memoir identifies it as the earliest specifically named song; the exact day was not preserved.
Read Jensen’s memoirMusic from the Tower of Jewels
During San Francisco’s Panama-Pacific International Exposition, loudspeakers installed on the Tower of Jewels projected phonograph concerts across the grounds. The exposition ran from February 20 through December 4; the dates and individual selections of the Magnavox concerts have not been reliably preserved.
View the surviving driverGolden Gate Park demonstration
A violin, piano, Hawaiian string ensemble, spoken word, and recordings by Luisa Tetrazzini and Alma Gluck filled the stadium. Attorney Thomas W. Hickey’s reading of the Gettysburg Address is the earliest clearly identified live speech in the formal demonstration.
Explore the technical history
Christmas music fills Civic Center
On Christmas Eve, a vast crowd gathered at San Francisco’s Civic Center to experience amplified sound on an unprecedented scale. Historical accounts place attendance at approximately 75,000 or more. Through a single Magnavox loudspeaker system, Jensen and Pridham presented speeches and several Christmas songs with a clarity and reach that astonished listeners across the plaza.
The name Magnavox comes from the Latin for “great voice.” The event demonstrated that one electrically amplified voice—or one musical performance—could become a shared experience for an entire civic gathering. It is remembered as one of the earliest successful large-scale uses of an electrically operated public-address loudspeaker system.
A voice heard above engines and at sea
During World War I, Jensen and Pridham developed a noise-neutralizing microphone that made speech intelligible over the roar of aircraft engines. The design used opposing acoustic paths to reduce surrounding noise while preserving the speaker’s voice—an early and influential form of acoustic noise cancellation.
Magnavox equipment also entered military and naval service, where powerful loudspeakers supported shipboard communication and public-address needs. The same principles that carried music across San Francisco now helped voices cut through machinery, wind, and the immense scale of large vessels.
View the noise-neutralizing microphone patentA governor’s voice crosses San Francisco
At the dedication of San Francisco’s new Civic Auditorium, California Governor Hiram Johnson spoke from his home approximately two miles away. A dedicated telephone line carried his voice to a Magnavox system inside the 12,000-seat hall—an early demonstration of amplified remote speech.
The Magnavox becomes a world-famous voice
At City Stadium in San Diego, President Woodrow Wilson stood before a crowd of approximately 50,000 people. Speaking into microphones connected to a Magnavox public-address system, his voice was projected through two enormous horns so clearly that listeners reportedly heard him from as far as a mile away. Pridham helped supervise the installation, while Jensen remained on the platform with the president.
For the first time, a U.S. president could address tens of thousands of people and be heard throughout the crowd. It was more than a technical achievement—it marked a revolution in public communication. From that moment, amplified sound became a powerful force in politics, civic life, and shared public experience.
Years later, Jensen reflected uneasily on that power. After witnessing dictators use amplified speech for mass propaganda, he expressed regret that the loudspeaker—created to let people hear music and one another—could also be used to manipulate enormous crowds.
Explore the AES history
Hear history in person
Meet “Maggie,” our original Magnavox R4.
Visit NEOTEMPO Studio in St. Helena to see—and hear—one of the original Magnavox R4 loudspeakers in person. Discover how Napa’s remarkable sound legacy lives on through wine, music, art, and a collection of sound systems spanning multiple eras.
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Further reading
