Tesla really invent the loudspeaker?
While I've seen nothing to indicate that Tesla invented the modern-day
loudspeaker as we know it, the book Prodigal
Genius by John J. O'Neill contains two passages that
might lead one to believe otherwise. The first account goes like
When the new telephone exchange was
finally started in Budapest in 1881, he [Tesla] was placed in charge of it.
. . . Here he made his first invention, then called a telephone repeater, or
amplifier, but which today would be more descriptively called a loud speaker--an ancestor of the sound
producer now so common in the home radio set. This invention was
never patented and was never publicly described, but, Tesla later
declared, in its originality, design, performance and ingenuity it would
make a creditable showing alongside his better-known creations that
From this scant description
it appears the instrument developed in Budapest might actually have been
an audio amplifier or booster and not an audio transducer. O'Neill's
second account provides an additional spin on the story.
. . . Several fundamental requirements were presented which will be
understood by any non-technical person who has had even slight experience with radio receiving sets: 1. An antenna, or
aerial wire; 2. A ground connection; 3. An aerial-ground circuit containing inductance
and capacity; 4. Adjustable inductance and capacity (for tuning); 5. Sending and receiving sets tuned to resonance with each other; and 6.
Electronic tube detectors. He had still earlier invented a loud speaker.
While O'Neill's description is
rather vague, in 1916 Tesla indeed spoke about a true electro-acoustic
that was part of a
. . . Whenever I received the effects of a transmitter, one of the most convenient and simplest ways [to detect them] was to apply a magnetic field to currents generated in a conductor, and when I did so, the low frequency gave audible notes.
One of the simplest devices I used in my experiments between my laboratory on South Fifth Avenue and [at] the Gerlach Hotel, and other places in and outside the city, was an instrument constructed in 1896 with a magnet which sometimes was so designed as to give me a very intense magnetic field up to 20,000 lines per square centimeter. In this [field] I placed a conductor, a wire or a coil, and then I would get a note which I amplified and intensified in many ways. From the characteristics of the audible note, I would immediately judge the quality of my apparatus.
When I speak of an audible note, I mean a note audible in a telephone as produced by the diaphragm of a telephone, or by a vibrating wire within the range of audibility. . . . I usually would transform the current in the receiving circuit and make as close a connection as possible and then tune the circuit to the vibrations. I would also mechanically tune the wire, according to the frequency, to the same note or to a fundamental. . . . You could hear it all over the place. . . . I could hear it from a distance. The vibrations were very vigorous. . . .
Tesla On His Work With Alternating Currents]
While by no means identical,
this device does bear some similarities to the electromagnet loudspeaker—especially
regarding the basic operating
principle—which preceded the permanent magnet loudspeaker that many of
us are familiar with. You be the judge. . . .