Past and present of speakers
In the early development of horns in the field of electro-acoustics, subject to the lag of the development of permanent magnets, moving coil horns were all driven by electromagnetics. After World War II, strong alloy magnets were successfully developed, and dynamic coil speakers evolved from electromagnetic to permanent magnets. This speaker greatly improves the stability and authenticity of the sound. The dynamic coil type is also the main way for modern speakers to sound. Although the electromagnetic type is low in cost, it is not effective, so it is often used on telephones and small headphones.
Sintered NdFeB
The magnets used in speakers today are mainly ferrites, neodymium nickel cobalt, and neodymium iron boron. Neodymium iron boron magnet is the core material of high-end loudspeakers, precisely sintered neodymium iron boron magnet. The magnetic properties of sintered NdFeB magnets are much higher than that of bonded NdFeB magnets, so the sound effect of horns using sintered NdFeB magnets is better. This feature makes neodymium-iron-boron magnets often used in high-end headphones. Such headphones have first-class sound quality, good flexibility, good details, good vocal performance, and accurate sound field positioning.
Application
In terms of applications, ferrites have relatively poor magnetic properties and require a certain volume to meet the driving force of the speakers, so they are generally used on larger acoustic speakers.
Due to the requirements of the working environment of the speaker, a suitable NdFeB can be selected according to the temperature resistance. For example: N (80 ° C), M (100 ° C), H (120 ° C), SH (150 ° C), UH (180 ° C), EH (200 ° C). Each temperature has different magnetic properties, such as N38, N40, N45,
The performance of neodymium-nickel-cobalt magnets is between that of neodymium-iron-boron and ferrite, but these two can work at a high temperature of 300 ° C, so there are special requirements for high temperature, which can be considered. But the price is relatively expensive.
The diameter of the speaker’s magnet
When we talk about how much magnetic the speaker is, we mean the diameter of the magnet in the horn. For example, 100 mag means that the diameter of the magnet is 100mm.
The magnet of the horn is not as large as possible: the magnets are divided into high density, low
density, strong magnetism, and weak magnetism. If it is a low density weak magnetism horn, no matter how it is assembled, it will not have a good effect, and the volume is large. Also inconvenient.
For the same magnetic material, the larger the diameter, the greater the magnetization saturation, the greater the magnetic field strength, the larger the power of the horn, the higher the sensitivity of the horn, and the better the transient response.
If the magnetization amount is different under the same conditions, the power, sensitivity, and transient performance of the speaker are different. Therefore, the larger the diameter of the horn magnet, the better.
PS: Generally speaking, the magnetic flux of neodymium-iron-boron magnets is much larger than that of ferrite, so using a neodymium-iron-boron magnet does not require a large diameter. Therefore, NdFeB is often used in small speakers, such as car audio.
Speaker motor
A speaker is an electroacoustic transducer that converts electrical energy into sound energy and radiates it into the air.
The most common speakers consist of three parts:
1. Vibration system, including cone cone, voice coil and centering support, etc.
2. Magnetic circuit system, including permanent magnets, magnetically permeable plates and field poles;
3. Auxiliary system, including basin stand, terminal board, blank holder and dust cover, etc.
Working principle of speaker magnetic circuit
When different electronic energy is transmitted to the coil, the coil generates an energy to
interact with the magnetic field of the magnet; this interaction will cause the paper plate to vibrate; at the same time, because the electronic energy changes at any time, the coil of the horn will move forward or backward, Therefore, the paper plate of the horn will follow the movement, and the movement will change the density of the air, and then generate sound. Here the role of the magnet is to assist vibration.
The electric current generates a magnetic field through the voice coil. When a changed electrical signal passes, the magnetic field changes its strength. The magnetic field of the permanent magnet at the bottom is attracted by the same sex and repulses the opposite sex. Because the drum paper is connected to the voice coil, it moves up and down. The vibration of the drum paper pushes the air to make a sound.
The stronger the magnet, the stronger the magnetic field strength, the more uniform the magnetic gap, and the more uniform the magnetic field distribution, the higher the sensitivity and efficiency of the magnetic circuit system. At present, in a magnetic circuit of a speaker, a ferrite or a neodymium iron boron is generally used as a permanent magnet.
Organizational structure of speaker motor
The speaker magnetic circuit is mainly composed of four parts:
1. Magnetically permeable column (T iron)
2. Magnetically permeable plate (washer)
3.Permanent magnet
4, frame
A: T-yoke (magnetically permeable column)
The role of T iron: magnetic permeability, fixed magnet
T iron material: SWRCH 6A
S (Steel steel), W (Wire wire), R (Ring ring), CH (Cold Heading)
Surface treatment of T iron: electroplating, baking paint, etc. (pre-treatment: surface blasting, turning pattern processing)
B. Washer (magnetically permeable plate)
Washer's role: magnetic permeability, connecting the magnet to the basin frame
Washer material: SPHC
S (Steel steel), P (Plate), HC (Heat Cut)
Washer's molding process: cold room stamping
Washer's surface treatment: electroplating, painting, etc. (pre-treatment: surface blasting, turning pattern processing)
C: magnet
The role of the magnet: to provide a constant magnetic field (storage of magnetic energy);
Magnet material: ferrite, neodymium iron boron, aluminum nickel cobalt, etc., among which different materials have multiple properties;
Magnet forming process: high temperature sintering after pressing
Surface treatment of magnets: ferrite is polished, neodymium iron boron is electroplated
D: FRAME
The role of the basin frame: to provide a supporting platform for the vibration system
Basin frame material: steel, aluminum, zinc, plastic, etc.
Processing technology of basin frame: steel is stamping, aluminum and zinc are die-casting, plastic is injection molding
Surface treatment of basin rack: electroplating, baking paint, spraying (plastic)
