What Is An Acoustic Phonograph?
In the now fully digital age, when we look back to the first mass-produced musical records and the phonograph, it seems hard to comprehend the advances in technology over time. With the current resurgence in vinyl records, it almost begs to be asked - what is an acoustic phonograph and how does it actually work?
The Victor machines in the acoustic era were all based on the flat disc design of original creator Emile Berliner. Using a lateral cut onto a flat disk, the discs are said to revolve at 78 RPM. As the grooves are tracked by the needle, vibration becomes mechanically coupled into the soundbox. The latter is made up of a thin mica diaphragm or aluminum. The diaphragm would vibrate which then provides a huge surface area where it can vibrate the air molecules into the tonearm. At this point, mechanical energy becomes converted to acoustical energy.
Most Victor machines are designed with a spring-powered, hand-wound motor that is used for spinning the turntable.
Then around the year 1913, Victrola models started to have the electric motors option. The more common spring drive was used in most Victrola models through the 1920s, but by 1928 most phonographs were sold with the electric motors.
Early models of the phonograph used an external horn. Victors with an external horn varied in design detail during the early years. The machines became more sophisticated as the knowledge on effective vibro-acoustic energy transfer from the disc to the outside room increased. The earliest models had the soundbox structure and integral horn with the horn’s neck being directly attached to the soundbox housing. At times, the horn’s weight gains support at its pivot point. This allows the horn/soundbox assembly to follow the record grooves.
Eventually, a tonearm design was developed. Together with the soundbox, the pair moved along the record while the horn is stationary. The mechanism was made possible with a simple pivot joint that’s found between the horn and the tonearm. Other design improvements resulted to the gradual expanding of the diameter from soundbox to horn. Even the soundboxes evolved in their design to improve their performance.
The internal-horn Victrola, which was developed in 1906, had a major design change where the tonearm elbow was inverted to route the sound into the horn that is now located inside the cabinet. The result is a piece of furniture that’s less intrusive while the integral doors found in front of the horn’s outlet provided the mechanism for adjusting the volume. Open the doors when you want the sound louder, close them for a quieter listening experience.