Static speakers
More than a hundred years ago, on February 14, 1876, Alexander Graham Bell proposed the most important patent in history, the "telephone." This invention allows human voices to travel further than shouting. Human beings have since understood the conversion relationship between sound and electricity, and have never tired of it.
In order to better play back the recorded sound, in 1910, S. G. Brown separated the driving force and diaphragm and invented the 'armature' armature earphone.
balanced headphones
In 1910, Baldwin invented the 'balanced armature' balanced armature headphones. Armature-type headphones have a movable iron piece (armature) set up in the middle of a U-shaped magnet. When current flows through the coil, the armature will be magnetized and repelled by the magnet, and at the same time drive the diaphragm to move. This design was low-cost. Although the effect was not good, it was an epoch-making invention at the time. This technology was mostly used in telephone receivers and small headphones.
In terms of technology for recording sound, Wente and Thuras designed the condenser microphone in 1917.
By the mid-1930s, electrostatic speakers were available based on the principle of condenser microphones. In the early 1950s, the American C. V. Bocciarelli proposed the 'constant charge' constant charge law. P. Walker independently developed the same theory during the same period and applied it to the famous Quad electrostatic loudspeaker design.
The basic principle of an electrostatic loudspeaker is Coulomb's law. It is usually made of a plastic diaphragm and inductive materials such as aluminum, which are vacuum vaporized. The two diaphragms are placed face to face. When one of the diaphragms is supplied with a positive current and high voltage, The other piece will induce a small current, and the air will be pushed through mutual attraction and repulsion to produce sound. Due to the light weight and small vibration dispersion of the electrostatic monomer, the electrostatic speaker works in the mid-to-high frequency band. The sound quality is cool and ethereal, full of characteristics, and it is easy to obtain cold and ethereal treble. However, its efficiency is not high, its sound pressure output is low, its dynamics are small, and its cost is relatively expensive, which are also its weaknesses.
