1. The principle of horn sound
A horn is actually a conversion device that converts electrical energy into sound. When different electronic energy is transmitted to the coil, the coil produces An energy interacts with the magnetic field of the magnet. This interaction causes the paper plate to vibrate. Because the electronic energy changes at any time, the coil of the horn will move forward or backward, so the paper plate of the horn will follow the movement. This action makes the air flow. The density changes to produce sound.
Second, what are the ways the speaker sounds
1. Moving coil type
The basic principle comes from Fleming’s left-hand law, Put a wire with current and the magnetic line of force perpendicular to the north and south poles of the magnet, and the wire will be moved by the interaction of the magnetic force line and the current. The membrane produces a back-and-forth motion. At present, more than 90% of cone monomers are of moving coil design.
2. Electromagnetic type
A movable iron chopper (armature) is set up in the middle of a U-shaped magnet. When the current flows through the coil, the armature will be magnetized and magnetized. The phenomenon of repulsion is generated, and at the same time, the diaphragm is driven to move. This kind of design is cheap but ineffective, so it is mostly used in telephone receivers and small earphones.
3. Inductive type
The principle is similar to the electromagnetic type, but the armature is doubled, and the two voice coils on the magnet are not symmetrical. When the signal current passes through the two armatures Motion for different magnetic fluxes to push against each other. Unlike electromagnetism, inductance can regenerate lower frequencies, but the efficiency is very low.
4. Electrostatic type
The basic principle is Coulomb’s law, usually a plastic diaphragm plus aluminum and other inductive materials are vacuum vaporized, two diaphragms Placed face to face, when one of them is applied with a positive current and high voltage, the other will induce a small current, and the sound will be produced by pushing the air through mutual attraction and repulsion. Due to its light weight and small vibration dispersion, the electrostatic unit is easy to obtain clear and transparent mid-high range, which is not enough for bass power, and its efficiency is not high, and it is easy to collect dust when using DC power. At present, manufacturers such as Martin-Logan have successfully developed a hybrid speaker of electrostatic and dynamic coil, which solves the problem of insufficient bass in the electrostatic body, and the electrostatic type is widely used in headphones.
5. Plane type
The first design developed by Japan SONY, the voice coil design is still the theme of the moving coil type, but the cone diaphragm is changed to the plane of the honeycomb structure The diaphragm, because of the cavity effect, has better characteristics, but the efficiency is also low.
6. Ribbon type
There is no traditional voice coil design, the diaphragm is made of very thin metal, and the current flows directly into the channel body to make it vibrate and produce sound. Since its diaphragm is the voice coil, it is very light, with excellent transient response and high frequency response. However, the efficiency and low impedance of ribbon speakers have always been a big challenge to amplifiers, and Apogee can be a representative. Another way is to have a voice coil, but the voice coil is directly printed on the plastic sheet, which can solve some of the low impedance problems. Magnepang is the leader in this type of design.
7. Horn type
The diaphragm works by pushing the air at the bottom of the horn. Because the sound is not diffused during transmission, the efficiency is very high, but the shape and length of the horn will affect the Tone, it is not easy to reproduce the low frequency, and now it is mostly used in giant PA systems or tweeters. Klipsch in the United States is a long-established horn speaker manufacturer.
8. Others
There is also a ribbon-style improved design developed by Dr. Haier in 1973, called Haier horn, which is theoretically very good, and Taiwanese users but very rare. Piezoelectric is a design that uses piezoelectric materials such as titanic acid to expand or contract with a voltage. Pioneer has improved the piezoelectric design with high polymers and used it in their tweeters. The ion horn (Ion) uses a high-voltage discharge to make the air a charged mass stopper. After applying an AC voltage, these free charged molecules will make sound due to vibration. Currently, it can only be used for monomers above high frequency. Philips has also developed an active feedback speaker (MFB), which is equipped with an active feedback circuit in the speaker, which can greatly reduce distortion.
Three. Common causes of speaker failure
1. If the speaker is overloaded for a long time, the speaker will burn out due to overheating. The temperature rises, causing some structural parts to melt, crack or burn. The temperature of the coil under normal use is 180 degrees Celsius, and it can be imagined under abnormal use!
2. Mechanical failure, the overloaded drive horn makes the paper tray move out of range and separate from the coil, or the coil and the coil seat are separated, the paper tray is folded or the horn support ring is torn, any of the above Once a situation occurs, it can cause the speaker to fail. When the hem or support ring is torn, the coils will rub against them as the tray assembly no longer hangs properly in the center. Small cracks may not be felt at first, but over time, as the crack becomes larger , the speaker will be broken.
3. The failure of the speaker may also be a combination of the above two methods. For example, the power amplifier suddenly outputs a large instantaneous energy. This energy can be the sudden loudness of the sound, and the speaker will have a strong vibration , so that the coil is out of the magnetic gap, and when it goes back, it may be eccentric and cannot return to its original position, which will cause the entire mechanical action to be brought forward by the paper tray and deviate from the original stop position. As a result, the paper tray has no sound. , but on the coil of the speaker where the energy continues to be transmitted, the coils leave the magnetic gap, because the magnetic gap is the best heat dissipation environment for the coil, but the coil has left the magnetic gap, so when the coil continues to receive the signal from the power amplifier, the coil is very It will quickly heat up and cause the coil to burn out. But this is relatively rare now, because the current horns are all long-stroke designs.
