In the beginning of XX century the Gramophone developed
by Berliner required large horn to amplify the recorded sound.
The large horns had good performance but they were clumsy.
In order to overcome such annoying condition, around 1905
the manufacturers launched in the market the fold horn concept
in such way it
could be assembled inside the sound reproducer cabinet.
Further to the aesthetical and practical aspects involved,
this new type of sound reproducer had another advantage since
the cabinet’ doors could be used as a kind volume control.
|Fig 339 - The gramophone.
In the early Gramophone machines models the disc were purely
hand operated and so it was quite difficulty to keep constant
the recorder speed at 70-rpm. Later on, the new reproducers
were supplied with a disc movement by winding motor, provided
with an ingeneous centrifugal force operated principle mechanical
device in order to keep the machine speed stable.
Originally the manufacturers chose the 70-rpm either to improve
the fidely of the sound as well as to become the machine suitable
for a proper reproduction of the early disc two minutes elapsed
time. Such recorder speed was kept for a while and later it
was changed to 74, 82-rpm and finally standardized at 78-rpm.
Around 1913, the engineers looked to replace the winding motor
for an electrical one.
|Fig 340 - The “orthophonic”
However, in the begining such new technological improvement
was quite slow considering the high price of the electrical
motor as well as that the electrical supply could not be found
In 1925, the company Victor talking Machine Company, launched
in the market the “orthophonic” system. It was
an advanced technological improvement as it replaced the former
mica membrane diaphragms by the ones made with a more resilient
material as Aluminium. The sound reproducers were still operating
in the mechanical-accoustical concept but they used now an
exponential fold horn.
In the early twneties the quality of sound reproductions was
deeply improved either by the aforementioned innovation as
well as the birth of the electrical recording.
Therefore in 1928, the valve amplifier required in the talking
movies, changed drastically the quality of sound recording
and playback and so the golden age of the mechanical-accoustical
sound reproducers came to an end. Fig 340