1. What is a good speaker?

From a scientific and objective perspective, a good speaker is one with wide frequency response, high sensitivity, high power, balanced curve, and accurate phase. When the speakers are matched with the power amplifier and the preamplifier, the phase is consistent, the frequency response curve is balanced and natural, and the subjective listening experience when the music is played back is bright, clear, soft, real and natural, which is a good sound (system).

A speaker with a wide frequency response has strong expressive power, high sensitivity means it is easy to push, high power means it is relatively more stable and safe, the curve is balanced, and the phase connection is reasonable and appropriate, so there will be no distortion due to internal energy consumption. As a result, various sounds can be reproduced truly and naturally, and the sound has strong layering, good separation, bright, clear and soft sound. Speakers with high sensitivity and high power are not only easy to push, but more importantly, their maximum sound pressure level within the stable and safe state can "beat the crowd", so you can get what you need without using too much power to drive. Sound pressure level.

In terms of subjective evaluation, due to different personalities, cultural accomplishments, artistic cognitions, preferences and standards, people have different opinions and descriptions.

Our comprehensive subjective evaluation is: a good speaker can be loud and shocking, but bright and clear without being harsh, has a mellow listening feel, is true and natural, and has good elasticity.

As a private room speaker, it must also have the requirements of being good at singing, durable in singing, durable (capable of Hi) and having a strong sense of envelopment.

2. What is a good power amplifier?

The criteria for a good power amplifier are reasonable efficiency, appropriate damping coefficient, wide frequency response, strong voltage transformation capability, normal balanced output waveform, and signal-to-noise ratio. High, low distortion, strong analytical power. When such a power amplifier is paired with a balanced high-quality speaker, the sound it produces appears clean, clear, with good separation, and a distinct listening experience.

Of course, the power amplifier, like the voice coil of the speaker, will generate very high temperatures during operation, so it must have reasonable circuits, high-quality components and good heat dissipation devices.

An amplifier that meets the above conditions and can cooperate with the speakers to produce soft, clear, transparent sound quality, and can work stably is a high-quality amplifier.

3. What is a good preamplifier?

The most important indicator of a good preamplifier is that the reverberation chip, op amp, and circuit should be good, and the functions should be appropriate, reasonable, sufficient, and adjustable Strong personality, real and natural voice.

4. What is a good microphone?

A good microphone is one that has real and natural sound (all the sounds it should have) when used with speakers, amplifiers, and preamps. If it is wireless, a U-segment wireless microphone that does not run or break frequency, is drop-proof, shock-proof and durable is better.

Speakers that can meet the above subjective and objective conditions are good speakers. Don’t be superstitious about whether the American, Japanese, or British speakers are good. In fact, the comparison is very simple: listen to the music you are familiar with. Just pick up the microphone and hum a few words while switching back and forth to compare.

Of course, if you have professional knowledge and testing equipment, in addition to subjective comparison of listening and singing effects, objective and scientific test comparison is also a good method. At any time, people's subjective consciousness will inevitably mislead themselves, but objective scientific data will not "deceive".

Audio knowledge:

1. Speaker

A speaker is a device that restores electrical signals into sound signals. The authenticity of the restoration will be used as a criterion to evaluate the performance of the speaker. important standards. Active speakers are speaker systems with power amplifiers (i.e. power amplifiers). The power amplifier and speaker sound system are integrated into one, and can be directly matched with general sound sources (such as Walkman, CD player, video player, video recorder, etc.) to form a complete audio combination.

With active speakers, there is no need to purchase another power amplifier, and you no longer have to worry about properly selecting power amplifiers and speakers. It is easy to operate, and its extremely high performance-price ratio is generally accepted by the working class.

According to different sounding principles and internal structures, speakers can be divided into several types such as inverted, sealed, flat, horn, labyrinth, etc. The most important forms are sealed and inverted. Mode. Sealed speakers are installed with speakers on a closed box, which is relatively low-efficiency; while the difference between inverted speakers is that they are equipped with a round inverted hole on the front or rear panel. It works according to the principle of Helmholtz oscillator, and has the advantages of high sensitivity, large power it can withstand and wide dynamic range. Because the sound waves on the back of the speaker have to be emitted from the phase guide hole, its efficiency is also higher than that of a sealed box. Moreover, the low-frequency sound pressure of the same speaker installed in a suitable inverted box will be 3dB higher than that obtained in a sealed box of the same volume, which is beneficial to the performance of the low frequency part, so this is why inverted boxes are widely used. important reason for popularity.

2. Power

There is no direct relationship between the sound quality of the speaker and the power. Power determines the maximum sound intensity that the speaker can emit. It feels like how powerful the sound from the speaker can be. According to international standards, there are two labeling methods for power: rated power (RMS: sine wave root mean square) and instantaneous peak power (PMPO power). The former refers to the maximum electrical power that the speaker can withstand without any damage after a certain interval and repeated a certain number of times when driving an 8° loudspeaker within the rated range. It specifies a continuous analog signal with a waveform. power. The U.S. Federal Trade Commission stipulated the power calibration standard in 1974: two channels are used to drive an 8-ohm speaker load, and the effective wattage measured when the harmonic distortion is less than 1 in the range of 20 to 20,000 Hz is the amplifier's effective wattage. Output power, the marked power is the rated output power. Usually, in order to cater to consumer psychology, merchants mark the instantaneous (peak) power, which is generally about 8 times the rated power. Imagine that the same TDA1521 power amplifier chip uses PHILIPS (maximum rated power 30W, THD = 10), and some products are nominally 360W, or even 480WP.M.P.O., is this possible? Does it make sense? So when purchasing a multimedia speaker Please refer to the rated power. The power of the speaker is mainly determined by the power of the power amplifier chip and the power of the power transformer. Taking into account some other factors, it can be calculated that if the rated power of the transformer is 100W, the power of the power amplifier chip that it can actually smoothly drive must be below 45W. , so by calculating the power relationship between the speaker transformer and the power amplifier, you can also verify whether the actual rated power of the speaker can reach the nominal value. The power of the speaker is not the bigger the better, but the application is the best. For a room of about 20 square meters for ordinary home users, the real power of 60W (referring to the effective output power of the speaker 30W x 2) is enough, but The larger the reserve power of the power amplifier, the better, preferably more than 2 times the actual output power. For example, if the speaker output is 30W, the power amplifier's power should be greater than 60W. For HiFi systems, the power of the amplifier driving the speaker is very high.

3. Frequency range and frequency response

The former refers to the range between the lowest effective playback frequency and the highest effective playback frequency that the sound system can reproduce; the latter refers to the range between a When an audio signal with a constant voltage output is connected to the system, the sound pressure generated by the speaker increases or attenuates as the frequency changes, and the phase changes with the frequency. This sound pressure and phase are related to the frequency. The changing relationship (change amount) is called frequency response, and its unit is decibel (Db).

The frequency characteristics of a sound system are often described by a frequency response curve in which the ordinate of the decibel scale represents power and the abscissa of the logarithmic scale represents frequency. When the sound power is 3dB lower than the normal power, this power point is called the high-frequency cutoff point and low-frequency cutoff point of the frequency response.

The frequency between the high-frequency cutoff point and the low-frequency cutoff point is the frequency response of the device; the curves of sound pressure and phase lag changing with frequency are called "amplitude-frequency characteristics" and "phase-frequency characteristics" respectively, collectively called "frequency" characteristic?. This is an important indicator for examining the performance of a speaker. It is directly related to the performance and price of the speaker. The smaller the decibel value, the flatter the frequency response curve of the speaker, the smaller the distortion, and the higher the performance. For example: the frequency response of a speaker is 60Hz ~ 18kHz /- 3dB. These two concepts are sometimes not distinguished and are called frequency response.

Theoretically, a frequency response of 20 to 20000Hz is sufficient. Sounds below 20Hz cannot be heard but can be detected by other human sense organs, that is, the so-called bass strength can be felt. Therefore, in order to perfectly play various musical instruments and language signals, the amplifier must achieve high-fidelity goals. Reproduce all harmonics of the tone. Therefore, the frequency band of the amplifier should be expanded, the lower limit should be extended to below 20Hz, and the upper limit should be raised to above 20,000Hz. The frequency response of the signal source (radio head, recorder, laser record player, etc.) is expressed in different ways. For example, the frequency response of FM stereo broadcasting specified by the European Broadcasting Union is 10/?2dB at 40~15000Hz, and the minimum frequency response index specified by the International Electrotechnical Commission for the recording socket is: 10/2.5/?4.5dB at 40~12500Hz (normal ), the actual achievable indicators are significantly higher than this value. The upper limit of the frequency response of a CD player is 20,000 Hz, and the low-frequency end can be very low, only a few Hz. This is one of the reasons why the CD player has good playback quality.

However, the harmonic components that make up the sound are very complex. The wider the frequency range, the better the sound is not. However, this is still basically correct for mid-to-low-end multimedia speakers. When labeling frequency response, we usually see the two terms "system frequency response" and "amplifier frequency response". You must know that "system frequency response" is always smaller than the range of "amplifier frequency response", so only label it ?Amplifier frequency response? means nothing and is just used to fool some uninformed consumers. Current speaker manufacturers generally mark the frequency response of the system in an overly large range. The high-frequency part is not much different, but the mark on the bass end is extremely unrealistic. Foreign famous-brand HiFi (high fidelity) speakers only mark around 4 or 50 Hz. , and two or three hundred wooden ordinary speakers in China dare to label this data, which is really laughable! Therefore, I would like to remind everyone that low-frequency sounds must be heard to be true, and do not easily believe the values ????on the leaflet. The music in multimedia speakers is mainly based on MP3 or CD music, songs, game sound effects, background music, and human voices and environmental sound effects in movies. Most of these sounds are medium and high-pitched, so when choosing a multimedia speaker You should pay more attention to its ability to express sounds in the mid- and high-frequency bands, rather than the low-frequency bands. If you really pursue cinematic effects, then a powerful subwoofer can definitely meet your needs.

4. Loudness

The strength of the sound is called intensity, which is determined by the amplitude (sound pressure) of the rapid change in air pressure. However, the human ear's subjective feeling of intensity is not consistent with the objective actual intensity. People call the subjective feeling of intensity loudness, and its measurement unit is also decibel (Db). It is based on the sound of 1000Hz sound at different intensities. The pressure ratio value is determined by l/10 of its commonly used logarithmic value. The reason for taking the logarithmic value is that the increase in intensity and loudness is not directly proportional, but the relationship between real numbers and logarithms! For example, when the sound intensity is 10 times louder, it sounds only one level louder (10dB). At 100 times, it sounds only two levels louder (20dB). For a 1000Hz sound signal, the lowest sound pressure that the human ear can feel is 2 x 10E-5Pa. This sound pressure level is set as 0dB. When the sound pressure exceeds 130dB, the human ear will not be able to bear it. Therefore, the dynamic range of human hearing is 0～130dB.

People have different perceptions of sounds of equal intensity and different frequencies; the higher the sound pressure level, the flatter the frequency characteristics of human hearing; the lower the sound pressure level, the smaller the frequency range of human hearing; frequency flt; 16~20Hz and fgt; 18~20KHz sounds, no matter how high the sound level, are inaudible to the human ear. Therefore, the hearing frequency of the human ear is 20Hz ~ 20KHz. This frequency band is called audio or audio frequency; regardless of the sound pressure, the human ear is most sensitive to sounds with frequencies of 3KHz ~ 5KHz.

Most people cannot feel signal level changes below 3dB. Therefore, 3dB is often used as the allowable frequency response curve variation range of sound systems.

5. Distortion

There are harmonic distortion, intermodulation distortion and transient distortion. Harmonic distortion refers to the distortion caused by the addition of high-order harmonic components that are not found in the original signal in sound playback; intermodulation distortion mainly affects the pitch of the sound; transient distortion is due to the presence of a certain inertial mass of the speaker. The vibration of the basin cannot keep up with the vibration of the instantaneously changing electrical signal, causing the difference between the original signal and the playback tone. It is more important in speakers and speaker systems, and directly affects the degree of restoration of sound quality, so this indicator is closely related to the quality of speakers. This item is often expressed as a percentage. The smaller the value, the smaller the distortion. The distortion of ordinary multimedia speakers is preferably less than 0.5, while the distortion of subwoofers is generally larger, and less than 5 is acceptable.

6. The sensitivity of the speaker (unit Db)

For every 3dB difference in the sensitivity of the speaker, the output sound pressure will double. Generally, 87 Db is the medium sensitivity, and 84 Db Below is low sensitivity, and above 90 Db is high sensitivity. The increase in sensitivity comes at the expense of increased distortion. Therefore, as a high-fidelity speaker, in order to ensure the restoration and reproduction capabilities of the tone, some sensitivity requirements must be reduced. But it cannot be said the other way round, a speaker with high sensitivity must have bad sound quality and a speaker with low sensitivity must have good sound quality. Speaker amplifiers with low sensitivity are difficult to drive (requiring a larger reserve power of the amplifier). So although sensitivity is an indicator of a speaker, it has nothing to do with the sound quality and timbre of the speaker.

7. Impedance

It refers to the ratio of the voltage and current of the speaker input signal. The input impedance of speakers is generally divided into two categories: high impedance and low impedance. Those above 16? are high impedance, and those below 8? are low impedance. The standard impedance of speakers is 8?. When the power amplifier and output power are the same, a low-impedance speaker can obtain greater output power, but if the impedance is too low, it will cause under-damping and bass degradation. Therefore, although this indicator has nothing to do with the performance of the speaker, it is best not to buy a low-impedance speaker. The recommended value is the standard 8?. The impedance of headphones is generally high impedance ?32? which is very common. The impedance of the power amplifier can generally be marked as equivalent impedance. For example, an output of 130W at 4° is roughly equivalent to an equivalent output of 80W. There is a term that is easily confused with it called "damping coefficient", which refers to the speaker impedance divided by the internal resistance of the amplifier source, ranging from about 25 to 1000. The speaker cone has to oscillate many times before it completely stops swinging after the electrical signal has disappeared. The voltage emitted by the coil generates current and magnetic field to prevent this parasitic movement. This is damping. The amplitude of the current, that is, the damping effect, depends on the internal resistance of the current flowing through the output stage of the amplifier. This resistance is much lower than the rated impedance of the speaker, with a typical value of 0.1?, but due to the series resistance and frequency division of the speaker's voice coil Due to the existence of series resistance in the network, the damping coefficient is difficult to achieve 50.

8. Signal-to-noise ratio

Refers to the ratio of the normal sound signal played back by the speaker and the noise signal (power) when there is no signal. Also represented by Db. For example, the signal-to-noise ratio of a certain tape recorder is 50dB, that is, the output signal power is 50dB greater than the noise power. The higher the signal-to-noise ratio value, the smaller the noise.

The International Electrotechnical Commission's minimum signal-to-noise ratio requirements are that the preamplifier is greater than or equal to 63dB, the post-amplifier is greater than or equal to 86dB, and the integrated amplifier is greater than or equal to 63dB. The optimal signal-to-noise ratio of the integrated amplifier should be greater than 90dB; the radio head: 50dB for FM stereo, in fact it is better to reach more than 70dB; the tape recorder is 56dB (ordinary band), but the signal noise after Dolby noise reduction Much improved than that. For example, after Dolby B noise reduction, the signal-to-noise ratio can reach 65dB, and after Dolby C noise reduction, the signal-to-noise ratio can reach 72dB (the above refers to ordinary bands); the signal-to-noise ratio of CD players can reach more than 90dB, and high-end It can even reach above l10dB. When the signal-to-noise ratio is low, the noise is serious when the small signal is input, and the sound in the entire range is obviously muddy and unclear. Therefore, it is not recommended to buy speakers with a signal-to-noise ratio lower than 80dB! And the subwoofer with a 70 Db subwoofer is not recommended for the same reason. .

9. Speaker material

Low-end plastic speakers have no sound quality because of their thin cabinets and inability to overcome resonance. Far better than inferior wooden speakers); wooden speakers reduce the sound coloration caused by cabinet resonance, and the sound quality is generally better than plastic speakers. Usually multimedia speakers are dual-unit, two-way designs. One smaller speaker is responsible for the output of mid-range and high-pitched sounds, while the other larger speaker is responsible for the output of mid-bass. When selecting speakers, the materials of these two speakers should be considered: the tweeter units of multimedia active speakers are mainly soft domes (in addition, there are titanium film domes for analog sound sources, etc.), which can reduce high frequencies when combined with digital sound sources. The stiffness of the signal gives people a gentle, smooth and delicate feeling. Multimedia speakers are now mostly made of soft domes such as silk membranes with better quality and PV membranes with lower cost. The bass unit determines the sound characteristics of the speaker, and it is relatively important to choose. The most common ones are as follows: paper cones, and there are also glued paper cones, paper-based wool cones, compressed cones, etc. Paper cone timbre Natural, cheap, good rigidity, light material and high sensitivity. The disadvantages are poor moisture resistance and difficulty in controlling the consistency during manufacturing. However, top HiFi systems are often made with paper cones because the sound output is very average and has good reproducibility. ; Bulletproof cloth, with wider frequency response and lower distortion, is the first choice for those who love strong bass. The disadvantages are high cost, complicated production process, low sensitivity and poor light music effect; wool woven basin, soft texture, It performs very well on soft music and light music, but the bass effect is not good, lacking strength and shock; PP (polypropylene) basin, which is widely popular in high-end speakers, has good consistency and low distortion, and performs well in all aspects Can be ordered. In addition, there are fiber diaphragms and composite material diaphragms that are rarely used in popular speakers due to their high prices, so we will not talk about them. Naturally, the larger the speaker size, the better. Large-diameter subwoofers can perform better in the low frequency range, which can be selected during purchase. Speakers made with high-performance speakers mean lower transient distortion and better sound quality. The speakers of ordinary multimedia speakers and subwoofers are mostly between 3 and 5 inches. Speakers made from high-performance speakers also mean lower transient distortion and better sound quality.

10. Structure and characteristics of speakers

Speakers can be divided into bookshelf type and floor-standing type in terms of structure. The former is small in size, clear in layers, and accurate in positioning, but has limited power. , the extension and volume of the low frequency band are insufficient, so it is suitable for music lovers who mainly enjoy high-fidelity music, and is also the first choice for our multimedia enthusiasts; the latter is larger in size, can withstand greater power, and has stronger volume and elasticity in the low frequency. He is good at expressing the overwhelming momentum and powerful shock, but if he does not do it well, he will be slightly lacking in layering and positioning. For fans of different music, this is also important content that should be understood before purchasing. Since PC users rarely have the conditions to place large floor-standing speakers, compact desktop bookshelf speakers should be the first choice for multimedia active speakers. In general: as long as the power amplifier module is properly designed, the bigger the cabinet, the bigger the speaker, and the more pleasant the sound will be.

11. Scalability

This refers to whether the speaker supports multi-channel simultaneous input, whether it has an output interface for passive surround speakers, whether it has USB input function, etc. The number of external surround speakers that can be connected to the subwoofer is also one of the criteria for measuring expansion performance. The interfaces of ordinary multimedia speakers mainly include analog interfaces and USB interfaces. Others, such as optical fiber interfaces and innovative digital interfaces, are not very common, so we will not introduce them in detail.

12. Sound effect technology

Hardware 3D sound effects technology is now more common, including SRS, APX, Spatializer 3D, Q-SOUND, Virtaul Dolby and Ymersion. Although they are implemented separately The methods are different, but they can all make people feel the obvious three-dimensional sound field effect, among which the first three are more common. They all apply the Extended Stereo theory, which performs additional processing on the sound signal through circuits to make the listener feel that the sound image direction has expanded to the outside of the two speakers, thereby expanding the sound image and giving people space. sense and three-dimensionality, producing a wider stereo effect. In addition, there are two sound enhancement technologies: active electromechanical servo technology (essentially utilizing the Helmholtz vibration principle), BBE high-definition plateau sound reproduction system technology and "phase fax" technology, which are also helpful in improving sound quality. Certain effect. For multimedia speakers, SRS and BBE technologies are relatively easy to implement and have good results, and can effectively improve the performance of the speakers.

13. Pitch

Refers to a signal with a specific and usually stable pitch. In layman’s terms, it refers to the pitch of a sound. It mainly depends on the frequency, but also on the intensity of the sound. Sounds with high frequencies are perceived as high-pitched by the human ear, while sounds with low frequencies are perceived by the human ear as low-pitched. Pitch changes with frequency (Hz) in an essentially logarithmic relationship. Different musical instruments play notes of the same frequency. Although their timbres are different, their pitch is the same, that is, the fundamental frequency of the sound they play is the same.

14. Timbre

The feeling of the timbre of a sound is also the characteristic quality that distinguishes one sound from another. When different musical instruments produce the same tone, their colors can be completely different. This is because although their fundamental frequencies are the same, their harmonic components are very different. Therefore, the timbre not only depends on the fundamental frequency, but also is closely related to the harmonics that are integral multiples of the fundamental frequency. This makes each instrument and each person have a different timbre.

15. Dynamic range

The ratio of the strongest to the weakest sound, represented by Db. For example, a band has a dynamic range of 90dB, which means that the weakest part is 90dB less powerful than the loudest part. Dynamic range is a ratio of powers and has nothing to do with the absolute level of sound. As mentioned before, the dynamic range of the human ear is from 0 to 130dB. The dynamic range of various sounds in nature also varies greatly. Generally speaking, the speech signal is only about 20-45dB, and the dynamic range of some symphonies can reach 30-130dB or higher. However, due to limitations of some factors, the dynamic range of the sound system can rarely reach the dynamic range of the band. The inherent noise of the recording device determines the weakest sound that can be recorded, while the maximum signal capacity (distortion level) of the system limits the strongest sound. Generally, the dynamic range of sound signals is set to 100dB, so it is good if the dynamic range of audio equipment can reach 100dB.

16. Total harmonic distortion (THD)

Refers to the extra harmonics in the output signal that are more than the input signal due to nonlinear components when the audio signal source passes through the power amplifier. Element. Harmonic distortion is caused by the system not being completely linear. We express it as the ratio of the root mean square of the newly added total harmonic component to the effective value of the original signal. For example, when an amplifier outputs 10V of 1000Hz and adds Lv of 2000Hz, there will be a second harmonic distortion of 10.

The sum of all additional harmonic levels is called total harmonic distortion. Generally speaking, the total harmonic distortion at the frequency of 1000Hz is the smallest, so many products use the distortion at this frequency as its indicator. However, total harmonic distortion is related to frequency, so the U.S. Federal Trade Commission stipulated in 1974 that total harmonic distortion must be measured within the full audio range of 20 to 20,000 Hz, and the maximum power of the amplifier must be when the load is 8 ohm speakers and the total Measured under the condition that the harmonic distortion is less than 1. The minimum requirements for total harmonic distortion stipulated by the International Electrotechnical Commission are: 0.5 for the preamplifier, and less than or equal to 0.7 for the integrated amplifier, but in fact they can all be less than 0.1: FM stereo tuners are less than or equal to 1.5, but in fact they can be less than 0.5 below; the laser record player can even achieve below 0.01.