Electrostatic speaker:
In order to better tell the story of human electroacoustic history, let's start with the first "telephone" that transmits human voice to a distant place. 100 years ago in February 1876, Alexander Graham Bell put forward the most important patent "telephone" in history. This invention makes human voice spread farther than shouting, and human beings understand the conversion relationship between sound and electricity from now on, and enjoy it.
In order to play back the recorded sound better, in 19 10, S. G. Brown separated the driving force from the diaphragm and invented the armature earphone.
Balanced armature earphone:
19 10, Baldwin invented the balanced armature earphone. Armature earphone is a movable iron plate (armature) installed in the middle of U-shaped magnet. When current flows through the coil, the armature will be magnetized, and the magnets will repel each other and drive the diaphragm to move. This design cost is low, although the effect is not good, but it was also an epoch-making invention at that time. This technology is mostly used in telephone handsets and small headphones.
In recording technology, in 19 17, Winter and Tourasse designed a condenser microphone.
In the mid-1930s, according to the principle of condenser microphone, electrostatic speaker appeared. In the early 1950s, American C. V. Bocciarelli put forward the law of "constant charge". P. Walker independently developed the same theory in the same period and applied it to the design of the famous Quad electrostatic speaker.
The basic principle of electrostatic loudspeaker is Coulomb's law. Generally, plastic diaphragms and sensing materials such as aluminum are evaporated in a vacuum. The two diaphragms are placed face to face. When positive current and high voltage are applied to one of them, the other will induce a small current, and air can be pushed to make a sound through mutual attraction and repulsion. Because of the light weight of electrostatic monomer and small vibration dispersion, electrostatic speaker works in the middle and high frequency band, with light and meticulous sound quality and rich characteristics, and it is easy to get clear and transparent middle and high notes. However, its low efficiency, low sound pressure output, small dynamics and high cost are also its weaknesses.
Electric speaker:
At the same time as Bell, different speaker types are proposed. As an amateur, Ernst W. Siemens (Siemens &; 1874,65438)1On October 20th, the founder of Halske Company applied for a patent for a prototype of an electric loudspeaker, in which a voice coil with a supporting system was made in a magnetic field to keep the vibration system moving axially. At that time, it was mainly used in the field of relays rather than speakers. 1877 14 February 14, Siemens applied for a patent for a loudspeaker, and pasted parchment on a moving voice coil as a sound radiator. Parchment can be made into an exponential cone, which is the first full-size loudspeaker in the phonograph era.
1898, Oliver lodge applied for the first patent of practical electric loudspeaker, which moved the voice coil into the magnetic gap between the inner and outer circular plates. Like many inventions, this great invention was too advanced at that time. The invention determines the structure of 99% modern dynamic speakers.
Twenty-five years later, in the 1920s, radio broadcasting appeared. C. W. Rice and E. W. Kellogg published an epoch-making paper "A New Type of Non-trumpet Unit", which introduced the direct loudspeaker in detail. The Radiola 104 loudspeaker designed based on this theory costs $250 and is very popular in the United States.
In the past 50 years, the basic principle of electric speakers has not changed, but the design details and components have been improved. Compared with the old products, the frequency response range and dynamic range have made great progress. Electric loudspeaker has become the mainstream in the current market because of its simple structure, excellent sound quality, low cost and strong dynamics.
Horn speaker:
Trumpet speakers originated from the phonograph. 1928, Winter and Silas produced their efficient loudspeaker receiver. The principle of horn speaker is that the diaphragm pushes the air at the bottom of the horn to work. Because of the high acoustic resistance, the efficiency is very high. However, because the shape and length of the horn will affect the timbre, it is not easy to reproduce the low frequency. Nowadays, high-efficiency trumpet is mainly used in the field of professional sound reinforcement.
Tape speakers:
In the process of the formation of the above speaker technology, people began to understand that the ideal transducer should use a thin diaphragm that can pass current, and everyone began to conceive a belt speaker.
Schottky and Gerlach of Siemens Halske applied for the first patent of belt loudspeaker in June 1923. It installs a horizontal wave-shaped pure aluminum film between the two poles of the magnet, which can reduce the longitudinal hardness and resonance frequency.
193 1 year, Olson and Massa produced tape microphones.
Belt speakers are mainly used in middle and high frequency bands. Because of its flat frequency response curve, extremely high upper frequency limit and very good transient effect, it can easily form a linear sound source.
Although the history of human electroacoustic is so tortuous and complicated, there are indeed many excellent innovative electroacoustic speakers, and in fact, the design of these innovative speakers has tortured many of the best electroacoustic scientists in the last century.