Speaker

In modern audio devices, speakers play a crucial role as the core component that converts electrical signals into sound signals, directly determining the quality of sound and the auditory experience. Whether it's the stunning sound effects brought by home theaters or the delicate sound reproduction at concerts, they all rely on the exquisite operation of speakers. Next, let's delve into every aspect of speakers and unveil their mysterious veil.

1、 Working principle: The miraculous transformation from electrical signals to sound

The operation of speakers is based on the principle of electromagnetic induction. When audio current passes through the voice coil of a speaker, the voice coil produces a changing magnetic field. The changing magnetic field interacts with the permanent magnet magnetic field of the horn, and according to the principle of electromagnetic force, the voice coil will vibrate under the action of a force. The voice coil is connected to the diaphragm of the speaker, and the vibration of the voice coil drives the diaphragm to vibrate synchronously. The vibration of the diaphragm drives the surrounding air to produce density changes, thereby forming sound waves that are perceived by our ears as sound.

This process may seem simple, but it actually contains complex physical principles and precise engineering design. In the process of converting electrical signals into sound, any slight deviation in any link may affect the quality of the sound. For example, factors such as the resistance and inductance characteristics of the voice coil, the magnetic field strength and uniformity of the permanent magnet, and the material and structure of the diaphragm can all have a significant impact on the fidelity, sound quality, and volume of the sound.

2、 Basic structure: precise combination of each performing its own duties

The speaker is mainly composed of three parts: magnetic circuit system, vibration system, and auxiliary system. Each part contains multiple key components that work together to restore sound.

（1） Magnetic Circuit System

The magnetic circuit system is the core part of the speaker that generates driving force, mainly including permanent magnets, magnetic plates, and pole cores. Permanent magnets provide a stable magnetic field, and their material and performance directly affect the sensitivity and sound quality of speakers. Common permanent magnet materials include ferrite, neodymium iron boron, etc. Neodymium iron boron permanent magnets have the characteristics of high magnetic energy product and high coercivity, which can provide a strong and stable magnetic field for speakers, enabling speakers to achieve high sensitivity and excellent sound quality performance even in a small volume. They are commonly used in speaker systems; Ferrite permanent magnets have the advantages of low cost and good stability, and are widely used in mid to low end horn products.

The function of the magnetic plate and pole core is to guide and concentrate the magnetic field generated by the permanent magnet, enabling the voice coil to move in a uniform and strong magnetic field, and improving energy conversion efficiency. They are usually made of soft magnetic materials with high magnetic permeability, such as silicon steel sheets, perovskite alloys, etc., which can effectively reduce magnetic resistance, enhance magnetic field strength and uniformity.

（2） Vibration system

The vibration system is responsible for converting the vibration of the voice coil into sound waves, mainly composed of the voice coil, diaphragm, and centering support plate. The voice coil is one of the key components of a speaker, usually made of enameled wire. When audio current passes through the voice coil, the magnetic field generated interacts with the magnetic field of the permanent magnet, driving the voice coil to vibrate. The number of turns, wire diameter, and winding method of the voice coil all affect the electrical and acoustic performance of the speaker. Generally speaking, the more turns there are, the greater the inductance of the voice coil, and the better the low-frequency response of the speaker, but the sensitivity may decrease; The thicker the wire diameter, the lower the resistance of the voice coil, the greater the current that can pass through, and the stronger the power carrying capacity of the speaker.

The diaphragm is a component that directly generates sound, and its material and structure play a decisive role in sound quality. Common diaphragm materials include paper, plastic, metal, composite materials, etc. Paper diaphragms have the characteristics of low cost and natural and soft sound, and are widely used in mid to low end speakers; Plastic diaphragms, such as polypropylene (PP) diaphragms, have good moisture resistance and rigidity, and produce clear and bright sound. They are commonly used in some entry-level and mid-range speaker products; Metal diaphragms such as aluminum film, titanium film, etc. have the characteristics of high rigidity and lightweight, which can achieve fast vibration response and make the sound clearer and more delicate. They are commonly used in speakers and audio equipment; Composite material diaphragm combines the advantages of various materials and can exhibit excellent performance in different frequency bands, making it a material commonly used in many high-quality speakers.

The function of the centering support plate is to fix the position of the voice coil, ensuring that it can move along the axial direction during vibration, while providing some elastic support for the voice coil, helping it quickly recover to its initial position after vibration. The centering support piece is usually made of elastic materials such as paper, cloth, or rubber, whose elastic coefficient and damping characteristics can affect the vibration performance and sound quality of the horn.

（3） Auxiliary system

The auxiliary system includes components such as the basin frame and dust cap. Although they do not directly participate in sound generation, they play an important role in ensuring the performance and service life of the speaker. The basin frame is used to fix and support various components of the horn, and it needs to have sufficient strength and rigidity to prevent resonance and deformation during the horn vibration process, which affects the sound quality. Common materials for basin frames include metal and plastic. Metal basin frames, such as aluminum alloy basin frames, have the advantages of high strength and good heat dissipation, and are commonly used for speaker systems; Plastic basin racks have the characteristics of low cost and light weight, and are widely used in mid to low end products.

The dust cap is installed at the center of the diaphragm, mainly to prevent dust, debris, etc. from entering the inside of the speaker, damaging key components such as the voice coil and diaphragm, and also to strengthen the diaphragm to a certain extent. Dust caps are usually made of the same or similar material as the diaphragm, and their shape and size can affect the high-frequency response and sound quality performance of the speaker.

3、 Type classification: diverse choices to meet different needs

According to different classification standards, speakers can be divided into multiple types, each with its unique characteristics and applicable scenarios.

（1） Classified by frequency range

Bass horn: mainly responsible for reproducing low-frequency sound signals, with a frequency range generally between 20Hz and 300Hz. The diaphragm area of a subwoofer is relatively large, usually over 10 inches, to enhance the radiation ability of low-frequency sound waves. Its characteristic is the ability to produce deep and powerful bass effects, creating a stunning auditory experience. It is commonly used in home theaters, car audio systems, and sound systems to depict low-frequency elements such as explosion scenes in movies and bass drums in music.

Mid tone horn: The playback frequency range is roughly between 300Hz and 3000Hz, which covers the main frequency components of human speech and most musical instruments. The diaphragm size of a mid-range speaker is moderate, usually between 4-8 inches. It can clearly reproduce the human voice and the mid frequency part of the instrument, making the sound fuller and rounder. It is commonly used in multi unit speaker systems and is used in conjunction with subwoofers and tweeters to achieve full frequency playback of sound.

High pitched speaker: responsible for reproducing high-frequency sound signals, typically within the frequency range of 3000Hz to 20kHz or higher. The diaphragm area of the tweeter is small to improve vibration speed and high-frequency response capability. Common diaphragm materials for high pitched speakers include silk film, metal film, etc. The silk film tweeter has a soft and delicate sound, suitable for expressing classical music and vocals; Metal film tweeters have higher resolution and penetration, and can clearly reproduce high-frequency details. They are commonly used in scenarios that require highlighting high-frequency effects, such as playing pop and rock music.

Full frequency speaker: capable of reproducing sound signals over a wide frequency range, generally covering most audio frequency bands from low to high. The advantages of full frequency speakers are simple structure, low cost, and no need for complex dividers. They are suitable for occasions where sound quality requirements are not particularly high, such as radios, small speakers, etc. However, due to its relatively balanced performance in various frequency bands, it is difficult to achieve the excellent effects of subwoofers and tweeters in low and high frequency bands, so it is less commonly used in audio systems.

（2） Classified by energy conversion method

Electric horn: also known as dynamic coil horn, is a widely used type of horn. Its working principle is based on electromagnetic induction. The working principle and basic structure of the speaker horn introduced earlier are based on electric horn. Electric speakers have the advantages of simple structure, low cost, and good sound quality, and are suitable for various types of audio equipment.

Electrostatic horn: The diaphragm vibrates and produces sound through the action of an electrostatic field. The diaphragm of electrostatic speakers is very thin and lightweight, capable of achieving fast and precise vibration, with extremely high resolution and sound quality reproduction. The sound performance is delicate and soft, especially good at expressing classical music and vocals. However, electrostatic speakers require specialized electrostatic amplifiers to drive, which is costly and has strict requirements for the usage environment, so their popularity is relatively low.

Piezoelectric horn: It works by utilizing the piezoelectric effect of piezoelectric materials. When a voltage is applied to the piezoelectric material, the material undergoes deformation, which drives the diaphragm to vibrate and produce sound. Piezoelectric speakers have the advantages of small size, low power consumption, and fast response speed, and are commonly used in portable devices such as mobile phones and electronic watches that require high space and power consumption. But its sound quality is relatively poor, with insufficient low-frequency response, and it is less commonly used in high-quality audio equipment.

Electromagnetic horn: It directly drives the diaphragm to vibrate through electromagnetic force, and its structure and working principle are different from electric horns. The advantage of electromagnetic speakers is high efficiency, but their sound quality performance is relatively average. Currently, their application range in the market is relatively narrow, mainly used in some special audio equipment and industrial fields.

4、 Technical parameters: an important indicator for measuring performance

The technical parameters of speakers are an important basis for measuring their performance, and understanding these parameters helps us choose speaker products that are suitable for our own needs.

（1） Rated power

Rated power refers to the power that a speaker can withstand during long-term normal operation. It is an important parameter that determines the volume and power carrying capacity of the speaker. It should be noted that rated power and high power are different concepts. High power refers to the maximum power that a speaker can withstand in a short period of time (usually no more than 1 second), beyond which the speaker may be damaged. When choosing a speaker, the rated power should be reasonably selected based on the actual usage scenario and the power of the amplifier to ensure that the speaker can work properly and not be damaged.

（2） Sensitivity

Sensitivity refers to the sound pressure level generated by a speaker when a certain power of audio signal is input. Generally speaking, speakers with higher sensitivity produce louder sound at the same input power. The unit of sensitivity is dB/W/m, which is the sound pressure level generated at a distance of 1 meter from the horn per watt of power. Sensitivity is an important indicator for measuring the efficiency of a speaker. For situations where high volume is required but the power of the amplifier is limited, choosing a speaker with high sensitivity can achieve better sound effects.

（3） Impedance

Impedance refers to the obstructive effect of a speaker on audio current, measured in ohms (Ω). Common speaker impedances include 4 Ω, 8 Ω, 16 Ω, etc. The matching of impedance and power amplifier is very important. If the impedance of the speaker does not match the output impedance of the power amplifier, it may cause sound distortion, insufficient power output, or even damage to the equipment. Generally speaking, the output impedance of the amplifier should match or be slightly lower than the impedance of the speaker to ensure that the amplifier can output sufficient power and maintain stable sound quality.

（4） Frequency response

Frequency response refers to the ability of a speaker to reproduce sound signals of different frequencies, usually represented by a curve. The ideal frequency response curve should be flat, meaning that the output sound pressure level of the horn in each frequency range is the same, in order to accurately reproduce the sound signal. However, in practice, due to limitations such as the structure and materials of the horn, its frequency response curve cannot be completely flat, and there will always be some fluctuations. The wider the range of frequency response and the smaller the fluctuation, the better the sound quality of the speaker, which can restore richer sound details and more accurate timbre.

5、 Application areas: Widely serving various audio scenarios

The application fields of speakers are very wide, covering multiple areas such as home entertainment, car audio, communication equipment, etc.

In the field of home entertainment, speakers are the core components of home theaters and Hi Fi sound systems. The home theater system can create a realistic sound field effect by combining multiple different types of speakers (such as subwoofers, front speakers, center speakers, surround speakers, etc.), allowing users to enjoy a stunning audio-visual experience like a movie theater at home; The Hi Fi audio system focuses on the restoration and purity of sound quality, presenting the details and emotions of music through high-quality speakers, meeting the pursuit of music enthusiasts for high-quality music.

In the field of specialized audio, speakers are widely used in stage performances, conference amplification, recording studios, and other places. Stage performances require speakers with strong power and excellent sound quality, which can clearly transmit sound in large venues and meet the auditory needs of the audience; Conference sound reinforcement requires speakers to produce clear and natural sound, accurately conveying the content of the conference; The recording studio requires speakers with extremely high frequency response accuracy and low distortion, so that the sound engineer can accurately judge the quality of the audio signal for post production and mixing.

In the field of car audio, the performance and installation position of speakers have a significant impact on sound quality. Due to the limited interior space and complex acoustic environment of automobiles, car audio speakers need to have good environmental adaptability and sound quality performance. At the same time, car audio systems also need to consider factors such as vibration and moisture resistance to ensure stable operation during vehicle operation.

In the field of communication equipment, speakers are used in devices such as mobile phones, walkie talkies, and telephones to play and receive sound. With the continuous development of mobile communication technology, higher requirements have been put forward for the sound quality, volume, power consumption, and other aspects of speakers in communication devices, which promotes continuous innovation and progress in speaker technology.

6、 Development trend: towards a higher quality future

With the continuous advancement of technology, speaker technology is also constantly developing and innovating, and will move towards higher quality, intelligence, miniaturization, and other directions in the future.

In terms of improving sound quality, the application of new materials and the improvement of manufacturing processes will continuously drive the advancement of speaker sound quality. For example, new materials such as nanomaterials and graphene have unique physical and chemical properties, which are expected to be applied to components such as the diaphragm of speakers, improving the vibration performance and sound quality of speakers; The development of 3D printing technology has also provided the possibility for personalized design and manufacturing of speakers, allowing for the customization of unique speaker structures according to different acoustic needs, achieving better sound quality effects.

Intelligence is one of the important trends in the development of speaker systems. With the popularization of technologies such as the Internet of Things and artificial intelligence, speakers will be more closely integrated with smart devices. Smart speakers can achieve functions such as voice control and automatic volume adjustment. They can also be linked with other smart devices to achieve automated control in smart home scenarios, bringing users a more convenient and intelligent living experience.

In terms of miniaturization, with the widespread application of portable electronic devices, higher requirements have been put forward for the volume and power consumption of speakers. In the future, speakers will develop towards smaller size and higher performance. By optimizing structural design and using advanced materials, speakers can be miniaturized and lightweight while ensuring sound quality, meeting the needs of portable devices.

As the core component of audio equipment, speakers play an irreplaceable role in the reproduction and propagation of sound. From working principles to structural composition, from type classification to technical parameters, from application fields to development trends, every aspect of it contains rich knowledge and technology. With the continuous development of technology, we have reason to believe that speakers will continue to innovate and improve, bringing us more wonderful and stunning auditory experiences.