What are the electric speakers?

During the same period as Bell, different speaker types were proposed. As a hobby, Ernst W. Siemens (founder of Siemens & Halske) applied for a patent for an electric loudspeaker prototype on January 20, 1874, which placed the voice coil with a support system in a magnetic field to maintain the vibration system. Axial movement. At that time it was mainly used in relays rather than speakers. On December 14, 1877, Siemens applied for a horn patent. A parchment was attached to a moving voice coil as a sound radiator. The parchment could be made into an exponential cone shape. This was the first actual horn in the phonograph era. type.
In 1898, Oliver Lodge applied for the first practical electric loudspeaker patent, which placed the voice coil in the magnetic gap between the inner and outer circular pole plates. Like many inventions, this great invention was too advanced at the time. This invention determines the structure of 99% of modern dynamic speakers in 2014.
Another 25 years later, in the 1920s, radio broadcasting appeared. C. W. Rice and E. W. Kellogg published the epoch-making paper "New Non-Horn Unit", which introduced the direct radiation loudspeaker in detail. The $250 Radiola 104 speaker designed using this theory became popular in the United States.
Over the past fifty years, the basic principles of electrodynamic loudspeakers have remained unchanged, only design details and components have improved. Frequency response range, dynamic range and other aspects have made great progress compared with older products. Electric speakers have become the mainstream of the market in 2014 due to their simple structure, excellent sound quality, low cost and high dynamics.
Electric speakers are the most widely used, and they are divided into three types: paper cone type, horn type and dome type. Only the first two are introduced here.
1. Paper cone speaker
Paper cone speakers are also called dynamic speakers.
It consists of three parts: ① Vibration system, including cone, voice coil and centering support piece; ② Magnetic circuit system, including Yongyi magnet, magnetic plate and field center column; ③ Auxiliary system, including cone Frames, wiring boards, edge presses and dust covers, etc. When an audio current passes through the voice coil in a magnetic field, a magnetic field changes with the audio current. This magnetic field interacts with the magnetic field of the permanent magnet, causing the voice coil to vibrate along the axis. Due to the simple structure of the speaker and the rich bass , soft sound quality and wide frequency range, but low efficiency.
2. Horn speaker
The structure of a horn-type speaker consists of two parts: a vibration system (treble head) and a horn. The vibration system is similar to a paper cone speaker, except that its diaphragm is not a paper cone, but a dome-shaped diaphragm. The vibration of the diaphragm radiates sound waves into the air through the horn (after two reflections). It has high frequency and loud volume, and is often used for outdoor and square sound reinforcement.