Speakers make sound by using magnetism and electric current to move air, creating sound waves.

Inside a speaker, there is a strong magnet that stays in place. A coil of wire, called the voice coil, sits in a small gap near this magnet and is attached to a thin surface called the diaphragm. When an audio signal is sent to the speaker, electricity flows through the voice coil. This creates a magnetic field, turning the coil into a temporary magnet.

Since the audio signal is always changing, the voice coil’s magnetism changes too. This makes it push and pull against the fixed magnet. As a result, the voice coil moves back and forth, carrying the diaphragm with it.

The diaphragm’s movement pushes the air, making areas of high and low air pressure—these are sound waves. When these waves reach our ears, we hear sound.

The speed of the voice coil’s movement depends on the audio signal. A fast-moving coil creates high-pitched sounds, while a slow-moving coil makes low-pitched sounds.

In short, electricity creates a magnetic force, which moves the voice coil, which moves the diaphragm, which moves the air—turning electrical signals into sound.
 

The core structure of a loudspeaker consists of a number of parts, each of which plays an important role in the production of sound.

1. Magnet

All speakers contain a magnet, either a permanent magnet or an electromagnet. The function of the magnet is to form a stable magnetic field, leaving a circular gap in the field for the voice coil and diaphragm to move through. The electromagnetic field generated when the voice coil is energized interacts with the magnet's magnetic field to drive the voice coil to vibrate, which in turn drives the diaphragm to produce sound. The strength and material of the magnet directly affects the efficiency and sound quality of the speaker. 


2. Voice Coil

The voice coil is a cylindrical coil of thin copper or aluminum wire suspended between the poles of the speaker magnet. The voice coil is placed in a magnetic gap. When current flows through the voice coil, it generates a magnetic field based on the principle of electromagnetic induction, which interacts with the fixed magnetic field of the loudspeaker magnet to create attractive and repulsive forces. This force causes the voice coil to vibrate back and forth within the magnetic gap, while driving the diaphragm to vibrate in synchronization, ultimately pushing the air to form sound waves. The diameter, number of turns, and material of the voice coil affect the sound quality, sensitivity, and power handling of the speaker.


3. Diaphragm

Diaphragm is a lightweight conical membrane, usually made of paper, plastic, metal or composite materials. Its function is to convert the vibration of the voice coil into air vibration (sound waves), so that the sound spread to the outside world.

When the voice coil vibrates, it pushes the air to create air pressure fluctuations, which are further amplified by the diaphragm and spread outward, eventually being picked up by our ears. The material and shape of the diaphragm have a significant effect on the clarity, frequency response and distortion of the sound.

♦ Harder materials (e.g. metal, ceramic) help to minimize high frequency distortion and improve resolution.

♦ Softer materials (e.g., paper, composite fibers) are better suited to provide a warm, natural tone.

The structural design of the diaphragm determines the speaker's performance in different frequency ranges, so different types of speakers use different diaphragm materials.


4. Spider

Spider is a wavy, flexible material located underneath the voice coil, usually made of cloth or composite fibers. Its role is to allow the voice coil in the vertical direction to stabilize the movement, while providing the appropriate rebound force to ensure that the voice coil can follow the audio signal vibration.


5. Surround

Surround is a ring of elastic material around the periphery of the diaphragm, usually made of rubber, foam or fabric. It allows the diaphragm to vibrate freely while limiting its range of motion to prevent deformation or damage.


6. Frame / Basket

The frame is a part of the speaker's enclosure that holds and supports the internal components. It is usually made of metal or high-strength plastic, to ensure that the speaker structure is stable and not affected by the external environment.


7. Dust Cap

The dust cap is located in the center of the diaphragm and is usually a raised circular cap. Its function is to prevent dust from entering between the voice coil and the diaphragm, while enhancing the high frequency response to a certain extent.
 

In broadcasting, meetings, speeches and other scenarios, we often need to amplify sound so that more people can hear it. The key to amplifying sound in a loudspeaker is that the amplifier provides more current to drive the voice coil to produce vibrations of greater amplitude, which drives the diaphragm to push more air, ultimately creating stronger sound waves, allowing sound to travel farther and louder.

1. Signal Amplification

Sound signals (such as microphone sound or radio signals) are very weak. In order for a speaker to produce a louder sound, these signals are first amplified by an amplifier (power amplifier) to increase the strength of the signal.

2. Driving the voice coil to vibrate

The amplified electrical signal enters the voice coil of the speaker. The voice coil vibrates in a magnetic field and moves back and forth according to the current. The stronger the current, the greater the vibration of the voice coil.

3. Drive the diaphragm

The voice coil is connected to the diaphragm of the speaker, and when the voice coil vibrates, the diaphragm vibrates with it. When the voice coil vibrates, the diaphragm vibrates with it. The vibration of the diaphragm pushes more air.

4. Producing a louder sound

The air pushed by the diaphragm creates sound waves, which are transmitted to our ears. When the signal is amplified, the voice coil vibrates more, pushing more air, and the sound becomes louder.
 

Speakers come in many designs, each with unique features that suit different needs.

Bass Reflex (Ported) Enclosure

This is one of the most common speaker designs. It uses a special opening (called a port) to let sound waves from inside the box escape. The size and shape of the port affect the deep bass sound. This design makes bass stronger, but if not done right, it can cause distortion.

Sealed Enclosure

A sealed speaker has no ports or openings. It keeps air trapped inside, which helps control vibrations for a cleaner sound. However, it requires more power to produce strong bass. This design is great for clear and tight sound, especially in high-quality audio systems.

Passive Radiator Enclosure

This design adds an extra, non-powered speaker cone (called a passive radiator) to help boost bass. When the main speaker moves, the passive radiator reacts to increase low-frequency sounds. It improves deep bass but may not respond as quickly as other designs.

Isobaric Enclosure

This type of speaker uses two drivers (speakers) working together to create stronger bass. They are usually placed face-to-face or in a special arrangement to increase low-frequency output. However, if not carefully designed, the sound may become unbalanced.

Transmission Line Enclosure

This design uses a long internal tube to guide sound waves and extend bass response. The longer the tube, the deeper the bass. However, this can also slow down the bass response, making it less suitable for fast, punchy sounds.

Horn Enclosure

Horn speakers use a flared shape to amplify sound and send it farther. They are often used in concerts and outdoor events because they can project sound over long distances. However, they are not the best for deep bass.

Loaded Horn Enclosure

This combines a transmission tube with a horn shape to improve bass response while still projecting sound far. It is ideal for large, high-energy audio systems that need powerful, far-reaching sound.

Compression Enclosure

This design places two speaker cones facing each other to push air and create deeper bass. The sound is released through tubes or openings. It can produce strong low-frequency sounds, but the design must be precise to avoid sound imbalances.

Each speaker design has its own strengths. Some focus on deep bass, others on clear sound, and some on long-distance projection. Choosing the right design helps create the perfect sound system for any need.

Speakers convert electrical signals into sound through electromagnetic induction and magnetic field interaction. Different frequencies determine the pitch, while different amplitudes affect the volume. A power amplifier boosts the signal, making the sound louder and clearer, enhancing the overall audio quality.