How much do you know about HiFi speakers—the basic knowledge of HiFi speakers?

How much do you know about HiFi speakers—the basic knowledge of HiFi speakers?

With the improvement of living standards, more and more Hi-Fi products have entered people's lives, and people are willing to spend more time and money to enhance the enjoyment of hearing. Many people have this question: why is HiFi so expensive? The same sound is released from the speaker, why is the sound of the HiFi speaker different? In fact, playing audio is far from being as simple as it seems. Some of the most basic parameter terms, sound units and types of speakers are already dizzying. First understand the basic knowledge of HiFi speakers, and under the guidance of these knowledge, you can roughly know why HiFi speakers are so different, so that enthusiasts can't stop.

1. Parameter nouns

Some parameters that are often seen in audio, including the frequency range, power, impedance, sensitivity, etc. of the sound, what do they mean?

The first is the frequency range, which refers to the range between the lowest effective sound reproduction frequency and the highest effective sound reproduction frequency. We know that the ideal audible frequency range of the human ear is 20HZ~20000HZ. In order to achieve this goal, the loudspeaker must consider the structure of the large amplitude and reduce the distortion, and generally the volume of the loudspeaker needs to be increased.

The second is the frequency response of the speaker, which refers to connecting a constant voltage output audio signal to the speaker system. When the frequency of the audio signal is changed, the sound pressure generated by the speaker increases or attenuates and the phase lags with the frequency. The phenomenon of change, the corresponding change relationship between sound pressure and phase and frequency is called frequency response. The amount of change is expressed in decibels (dB). This indicator is an important indicator for assessing the quality of the speaker. The smaller the decibel value, the flatter the frequency response curve of the speaker and the smaller the distortion.

When it comes to distortion, there are generally three types, namely harmonic distortion, intermodulation distortion and transient distortion. Harmonic distortion refers to the addition of high-order harmonic components that are not in the original signal to the reproduced sound.

Intermodulation distortion is the process of the speaker replaying the sound source. Due to the inhomogeneity of the magnetic field in the magnetic gap and the nonlinear deformation factor of the support system, a new frequency component that is not in the original signal will be generated. Therefore, when the new frequency signal When it is added to the speaker with the original frequency signal, it will be modulated to generate another new frequency. Therefore, in the playback frequency of the speaker, in addition to the original signal, there are two new frequencies that are not in the original signal. This distortion for intermodulation distortion.

The transient distortion of the speaker system refers to a transmission waveform distortion caused by the mass inertia of the speaker vibration system. Due to the mass inertia of the loudspeaker, the vibration of the paper cone cannot keep up with the instantaneously changing electrical signal, which causes the distortion of the transmission waveform of the playback sound, resulting in changes in the frequency spectrum and timbre. The quality of this indicator is extremely important in the speaker system and speaker unit, and it directly affects the sound quality and the degree of timbre restoration.

There is also the impedance and sensitivity of the speaker. Impedance refers to the ratio of the signal voltage input by the speaker to the signal current. The preferred values of speaker impedance stipulated in the national standard of our country are 4Ω, 8Ω, 16Ω (international standard recommended value is 8Ω). The nature is not the same.

The sensitivity of the speaker refers to the sound pressure level measured at a distance of 1m from the geometric center of each speaker unit on the front of the speaker when the input power to the speaker in the speaker system is 1W. What needs to be pointed out here is that although the sensitivity is an indicator of the speaker, it has nothing to do with the sound quality and timbre. It only affects the loudness of the speaker, and the loudness of the speaker can be improved by increasing the input power.

2. Sound unit

After introducing some basic parameters of the speaker, let's understand the categories of each unit on the speaker, which are generally divided into three frequency bands: high, medium and low.

1. High frequency speaker unit

The tweeter, as the name suggests, is a speaker unit for reproducing high-frequency sounds. Its structural forms mainly include horn type, cone type, ball top type and aluminum belt type.

The horn-type tweeter has strong directivity, and can feel powerful energy on the front of the horn, and is mostly used for high-power sound reinforcement.

The cone-type tweeter is more common in old-fashioned speakers because the diaphragm area is too large and heavy, and the high-frequency characteristics are not as good as other types of tweeters.

The dome tweeter is currently the most commonly used tweeter in home speakers and small monitor speakers. The dome tweeter can be divided into positive dome unit and reverse dome unit from the dome structure; from the dome material, it can be divided into two categories: hard dome and soft dome.

The diaphragm material of the hard dome treble includes aluminum alloy, titanium alloy, magnesium alloy, titanium alloy composite film, glass film and so on. The treble played back by the hard dome tweeter has a bright tone and a metallic feel. The excellent aluminum alloy and titanium alloy composite film dome tweeter can also better express classical music and human voice.

There are several kinds of diaphragm materials for soft dome tweeters, such as silk film, silk film, rubber film and bulletproof cloth film. When the soft-dome tweeter replays music, the high-pitched sound is flexible and relaxed, and has a good natural expression. It is especially handy when expressing classical music, human voice and other music with standard listening concepts.

2. Mid-frequency speaker unit

The frequency response curve of the mid-frequency speaker is flat, and the effective frequency response range is greater than the width of the sound-emitting frequency band it bears in the system. The impedance and sensitivity are consistent with the low-frequency unit. The midrange unit generally has two types of cone and dome, and its diaphragm is mainly made of soft materials such as paper cone and silk film, and occasionally there is a small amount of alloy dome diaphragm.

3. Low frequency speaker unit

The quality factor of the subwoofer is also different for various speakers. Generally speaking, the larger the caliber, magnet and voice coil diameter of the woofer, the better the low-frequency reproduction performance, transient characteristics, and higher sensitivity.

The structural form of the woofer is mostly cone type, and a small amount is flat type. There are many types of diaphragms for woofers, including aluminum alloy diaphragms, ceramic diaphragms, carbon fiber diaphragms, glass fiber diaphragms, acrylic diaphragms, paper diaphragms, and so on. The woofer with aluminum alloy diaphragm and glass fiber diaphragm generally has a relatively small caliber and relatively high power, while the woofer with reinforced paper cone and glass fiber diaphragm has more accurate timbre when replaying music, and the overall balance is good.

3. Types of speakers

Finally, let’s talk about the types of speakers. Nowadays, the shape of HiFi speakers can be said to be varied, but the more common ones are still mainly rectangular. The box structure mainly includes airtight boxes, reflection boxes, transmission lines, passive radiators, and coupling cavities. And so on.

The closed speaker is the speaker system with the simplest structure, which is composed of speaker units installed in a fully sealed box. It can completely isolate the forward radiation sound wave and the rear radiation sound wave of the speaker, so that the lowest resonance frequency of the speaker rises. The sound of the closed speaker is a bit deep, but the bass analysis is good.

Bass reflex speakers are also called inverted speakers. There is a sound outlet on its box body, and there are many opening positions and shapes. When the sound wave radiated backward by the loudspeaker is reversed through the conduit, it is radiated from the sound outlet to the front and superimposed in phase with the sound wave radiated forward by the loudspeaker. It can provide a wider bandwidth than the closed type, and at the same time has higher sensitivity and Less distortion. This kind of speaker can reproduce rich bass with a smaller cabinet, and is currently the most widely used type.

The transmission line speaker is named after the transmission line of classical electrical theory, and there is a sound pipe made of sound-absorbing wallboard behind the speaker. In theory, it is used to attenuate the sound waves coming from the back of the cone to prevent it from being reflected to the open end and affect the sound radiation of the woofer, but in fact, the transmission line speaker has a slight damping and tuning effect, which increases the frequency of the speaker near the resonance frequency or The following acoustic output. Usually the sound conduit of this kind of speaker is mostly stacked in a labyrinth shape, so it is also called a labyrinth or a labyrinth.

The passive radiating speaker is a branch of the bass reflex speaker, also known as the empty paper cone speaker. Its opening sound outlet is replaced by an empty paper cone without a magnetic circuit and a voice coil. The basin support assembly creates a resonance that enhances the bass. The main advantage of this kind of speaker is that it avoids the unstable sound generated by the reflection of the sound hole, the standing wave has little influence, and the sound is clear and transparent.

The coupled cavity speaker is a box structure between the closed type and the bass reflex type. Its output is output from the sound hole driven by one side of the cone, and the other side of the cone is coupled with the closed box. The advantage of this kind of speaker is that the amount of air pushed by the speaker is greatly increased at low frequencies, so the distortion is reduced and the power withstand is increased.

Different cabinets have their own acoustic design concepts. Speakers with different cabinet structures produce different sound effects, which are suitable for different venues and personal preferences. There is no absolute distinction between strong and weak.

The above is some basic knowledge about HiFi speakers. This is just a part of a HiFi system. In addition, there are audio sources, power amplifiers, cables, etc. There are also many knowledge worth studying.

After understanding these knowledge one by one, slowly adjust the sound you like, and better feel the charm of HiFi music.