[Home Theater Network] No matter what you call it, speakers, speakers, speakers, this thing that can restore the sound, has been through the first century. In fact, the process of trumpet development is not smooth. Scientists have tried their best to let the original sound reappear. However, this goal has not yet been achieved. Instead, different sounding methods have been adopted. Different manufacturing methods and materials have been used to make the speakers bloom. The most brilliant and splendid field in the audio world.
Fantasy more than a hundred years ago
In 1818, the second wife of the poet Shelley, Mary, described her scientist in the famous science fiction novel "Frankenstein", synthesizing a horrible monster with a disintegrated body, regaining life after being energized, and everyone was at the time There is endless confidence. In 1874, Bell, who invented the telephone, tried to make a "sound analyzer". He really used the corpse of the disintegration as a material to make a "Phonautograph" from the eardrum and the ear bones. This machine can draw a sound wave map but cannot reproduce the sound.
On July 18, 1877, Edison experimented with metal film and stylus recording. He sang a song about "There is a little sheep in Mary" on the metal foil. When the stylus pinch the vibration signal picked up by the horn, The people present were all dumbfounded because they heard Edison singing in the machine, which was the birth of the phonograph. Today, let readers appreciate the phonographs a hundred years ago. You must not imagine that the "sound" with insufficient bandwidth, no dynamics, unusual noise, and serious distortion can actually be popular. Soon the original horn was replaced by a reed horn. A horn was placed at the front end of a horseshoe magnet with a swingable metal piece in the middle of the coil. When the audio signal current passed through the coil, the magnetic field changed to make the metal The piece oscillates and sounds with the paper cone. This design is still not ideal, but it is the basis of the sound of the paper cone in the future; while the paper cone is made into a cylindrical shape, the magnet and the reed are placed in the cylinder, which can spread to all sides, which has become a non-directional speaker in the future. Indiscriminate.
In fact, as early as 1877, Erenst Verner of Siemens in Germany obtained the patent of the moving coil type according to Fleming's left-hand law. In 1898, Sir Oliver Lodge of the United Kingdom further invented the cone-shaped horn according to the principle of the telephone megaphone. It is very similar to the modern horn that we are familiar with, and Sir Lodge called it "roaring phone." However, this invention could not be used, because it was not until 1906 that Lee De Forest invented the three-pole vacuum tube, and it was a few years later to make the available amplifier, so the cone speaker was only popularized in the 1930s. Another reason is that the new record, recorded electronically in 1921, has come out. It has a better dynamic range (up to 30 dB) than traditional mechanically-engraved records, forcing people to try to improve the characteristics of the speakers.
In 1923, Bell Labs decided to develop a complete music reproduction system, including new phonographs and speakers, stereo recordings, MC phonographs, stereo stencils, etc., which were invented in this wave of action. The responsibility of developing the speaker is on the two engineers CW Rice and EW Kellogg. The equipment they used was unprecedented, including a 200-watt vacuum tube expander, and many of Bell's own recordings. The various speakers developed by Bell Labs over the years - like Lodge's The cone-shaped horn is a prototype, a compressed air horn that uses a diaphragm to control the compressed airflow, a corona discharge horn (today called an ion-driven driver), and an electrostatic horn. It wasn't long before Rice and Kellogg selected two designs from a variety of styles - cone and electrostatic, which decided to make the speaker a different direction: traditional and innovative.
Moving ring speaker
The moving coil type horn is evolved from the foundation of the reed horn. There is a cylindrical coil in the middle of the ring magnet. The front end of the coil is directly fixed on the cone or diaphragm, but the magnetic current is changed in the coil, and the magnetic field is changed. It will move back and forth to affect the paper cone. At the beginning of the dynamic horn, it was difficult to match the strength of the permanent magnet. Therefore, the electromagnetic design was used, and another coil was wound around the magnet to generate a magnetic field. This design has been popular for a long time. However, the electromagnetic horn has its problems. For example, the DC pulse of the electromagnetic coil easily generates AC noise interference of 60 Hz and 120 Hz; and the current intensity of the electromagnetic coil varies with the audio signal, causing new instability factors.
During the Great Depression of the 1930s, the Edison phonograph company closed down, and other people couldn't get anywhere. It needed to expand the machine-driven speakers, so the promotion was not smooth. The old Victorla phonograph was still popular until the Second World War. After the second war, the economy took off, and various new audio accessories became popular. The cone-shaped horns were once again severely tested. During this period of time, due to the development of strong alloy magnets, the moving-ring horns have all changed from electromagnetic to permanent magnets. The shortcomings of the past have been swept away. (In addition to the natural magnet cobalt, there are also Alnico and Ferrite magnets, except magnetic flux. In addition to density, natural magnets have superior characteristics. In recent years, high-grade horns have neodymium magnets. In order to cope with the advent of LP and the progress of the Hi-Fi system, the cone horn horn sought reform on the paper pot material. Commonly used to make woofers with thicker materials, light and hard diaphragms as high-pitched sounds; or different sizes of horns assembled into coaxial units; there are also horns in front of high-pitched horns into compression horn tweeters; The treble horn is hidden behind the bass cone. In 1965, Harbeth in the UK invented the Bextrene plastic diaphragm, which is a major advancement in materials. This soft but high damping coefficient product is still visible on KEF and some British speakers. Later, Harbeth also invented a polypropylene plastic diaphragm. This new material has a higher internal damping coefficient and is lighter in weight. It is still used by many speakers.
When the engineer designed the horn, it turned into two directions of thinking: the woofer sought a breakthrough in the structure of the speaker; the tweeter improved the unit. So some of the new designs that appeared at this time were almost all tweeters. A more successful design is an electrostatic horn.
Electrostatic horn
Earlier mentioned Bell Labor's Rice and Kellogg experimental horns, the electrostatic horns they make are as large as the door panels, and the diaphragm is made of gold-coated foil from the pig's large intestine (plastics are not yet on the market). When the illuminating light of the vacuum tube shines, the bright golden behemoth has a hypnotic effect, and the laboratory air is filled with the smell of pig intestines and the smell of ozone. The two scientists may think of "the Frankenstein" and the Bell made of the ear of the dead. The recorder." But after the sound began, its dazzling sound and realistic sounds made everyone scared. They understood that a new era has arrived. However, Rice and Kellogg encountered an insurmountable problem when designing an electrostatic horn: a large diaphragm was needed to regenerate the complete bass. In the case that the technology was difficult to break through, Bell Labs had to turn to the cone horn, which caused the stagnation. The electrostatic horn has been silent for thirty years.
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