What are the performance indicators of the speakers?

1, power

The power determines the maximum sound that a speaker can emit, and it feels like it is how loud the sound produced by the speaker can be. According to international standards, there are two ways to label power:

(1) Rated power (RMS: sine wave root mean square): Refers to driving an 8 ohm speaker within the specified range. Specifies that the waveform holding notebook horn has a broken semaphore analog signal. After a certain interval and repeat a certain number of times, the speaker The maximum electric power that does not cause any damage;

(2) Instantaneous peak power (PMPO power): refers to the maximum power that the speaker can withstand in a short time.

The U.S. Federal Trade Commission set the standard for power calibration in 1974: an 8-ohm speaker load driven in two channels, and the effective wattage measured when the harmonic distortion is less than 1% in the 20 to 20000 Hz range is the amplifier's The output power, the marked power is the rated output power.

The power of the speaker is mainly determined by both the power of the power amplifier chip and the power of the power transformer. For an average home user's room of about 20 square meters, the true 60W power (refer to the speaker's effective output power 30W x 2) is sufficient, but the power amplifier's reserve power is better, the best is the actual output power 2 times more. For example, the speaker output is 30W, then the power amplifier's ability is better than 60W.

2, frequency range and frequency response

(1) Frequency range: It refers to the range between the playback frequency and the highest effective playback frequency that the audio system can play back;

(2), frequency response qq non-mainstream symbology: refers to a constant voltage output audio signal and the system is connected, the sound pressure generated by the speaker with the frequency of the increase or attenuation, the phase occurs with the frequency The phenomenon of change, this type of sound pressure and the associated change in phase and frequency (change) is called the frequency response in decibels (Db).

The frequency characteristics of the sound system are usually described by the ordinate scale of the decibel scale and the frequency response curve of the frequency expressed by the abscissa of the logarithmic scale.

High Frequency Cutoff Point and Low Frequency Cutoff Point of Frequency Response: 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 cut-off point and the low frequency cut-off point is the frequency response of the device; the curves of the sound pressure and phase lag with frequency change are called “amplitude frequency characteristics” and “phase frequency characteristics”, respectively. characteristic". The smaller the decibel value, the flatter the frequency response curve of the speaker, the smaller the distortion and the higher the performance. Such as: A speaker frequency response is 60Hz ~ 18kHz +/- 3dB. These two concepts are sometimes not distinguished and are called frequency response.

Theoretically speaking, the bubble hall speaker script says that the frequency response from 20 to 20000 Hz is sufficient. Sounds lower than 20Hz, although not heard by human sense organs, can sense the so-called bass intensity. Therefore, in order to perfectly play a variety of musical instruments and speech signals, the amplifier must achieve high-fidelity goals. Replays each harmonic of the tone.

4, loudness

The strength of the sound is called intensity, which is determined by the magnitude of the pressure (sound pressure) at which the pressure changes rapidly. However, the subjective feeling of the human ear is not consistent with the objective actual intensity. People refer to the subjective feeling of strength and weakness as loudness, and the unit of measure is also decibel (Db), which is based on the sound of 1000Hz sound at different intensities. The pressure ratio is determined by 1/10 of its commonly used logarithmic value. The reason for taking the logarithmic value is that the increase in intensity and loudness is not proportional, but the relationship between true number and logarithm! For example, when the sound intensity is as large as 10 times, it sounds only one level (10 dB), and when the intensity is 100 times, it sounds two levels (20 dB). For a 1000Hz sound signal, the lowest sound pressure the human ear can feel is 2×10E-5Pa, and the sound pressure level is set to 0dB. When the sound pressure exceeds 130dB, the human ear can't bear the volume of the small horn. The dynamic range of human ear hearing is 0-130dB.

People have equal intensity and different frequency sound sensations; the higher the sound pressure level, the flatter the human auditory frequency characteristics; the lower the sound pressure level, the smaller the human auditory frequency range; the frequency f<16-20 Hz and f > 18 to 20 KHz sound, no matter how high the sound level, the human ear can not hear. The auditory frequency of the human ear is from 20Hz to 20KHz. This frequency band is called audio frequency or audio frequency. Regardless of the sound pressure level, the human ear is most sensitive to the sound of frequencies from 3KHz to 5KHz. Most people cannot feel the signal sound level mutation below 3dB, so the audio system often takes 3dB as the allowable frequency response curve variation range.

5, distortion

There are harmonic distortion, intermodulation distortion and transient distortion. Harmonic distortion refers to the distortion caused by the higher harmonic components that the original signal does not have in the playback of the sound; the intermodulation distortion mainly affects the pitch of the sound; the transient distortion is because the speaker has a certain inertial quality. The difference between the original signal and the playback sound caused by the vibration of the bowl cannot keep up with the vibration of the instantaneously changing electrical signal. It is even more important in the speaker and speaker system, and it directly affects the degree of reduction of the sound quality. This is usually expressed as a percentage. The smaller the value is, the smaller the distortion is. The distortion of ordinary multimedia speakers is better than less than 0.5%, and usually the subwoofer distortion is generally larger, less than 5% can be accepted.

6, the speaker's sensitivity (unit Db)

The sensitivity of the speaker is 3dB worse, and the output sound pressure is doubled. Generally, 87Db is the sensitivity, 84Db is the low sensitivity, and 90Db is the high sensitivity. The increase in sensitivity is at the expense of increased distortion. Therefore, as a high-fidelity speaker, it is necessary to reduce the sensitivity of the tone to ensure that the tone's degree of reduction and reproducibility. However, it cannot be said that high-sensitivity speakers must have good sound quality and low-sensitivity speakers must be good. Speaker amplifiers with low sensitivity are difficult to drive (requires more power for the amplifier). So although the sensitivity is an indicator of the speaker, it has nothing to do with the sound quality of the speaker.

7, impedance

It refers to the voltage-to-current ratio of the speaker input signal. Speaker input resistance Multi-tone speaker resistance is generally divided into two types of high impedance and low impedance, higher than 16Ω is high impedance, lower impedance than 8Ω, the speaker's standard impedance is 8Ω.

In the same power amplifier and output power, low-impedance speaker can get a larger output power, but the impedance is too low will cause under damping and bass degradation and so on. So although this indicator has nothing to do with the performance of the speakers, it is best not to buy low-impedance speakers. The recommended value is the standard 8Ω. The impedance of the headphones is generally high impedance – 32Ω is common. The impedance of the amplifier can generally be labeled as an equivalent impedance, such as a 130W output at 4Ω, which is roughly equivalent to an equivalent 80W output. There is a term that is easy to confuse, called the "damping factor," which is the impedance of the speaker divided by the internal resistance of the amplifier's source. The range is about 25 to 1000. The speaker cone still oscillates several times after the electrical signal has disappeared to completely stop the swing, and the voltage generated by the coil generates a current and a magnetic field to prevent this parasitic movement, which is damping. The magnitude of the current, which is the effect of the damping, depends on the fact that the current flowing through the output stage of the amplifier has no small speaker resistance. This resistance is much lower than the speaker's rated impedance, typically 0.1Ω, but due to the series connection of the speaker's voice coils The resistance and the series resistance of the crossover network exist, 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 to the noise signal (power) when there is no signal. Also denoted by Db. For example, the signal-to-noise ratio of a cassette tape recorder is 50dB, that is, the output signal power is 50dB greater than the noise power. The higher the SNR value, the lower the noise. The minimum requirement for the SNR of the International Electrotechnical Commission is that the preamplifier is greater than or equal to 63dB, the postamplifier is greater than or equal to 86dB, and the integrated amplifier is greater than or equal to 63dB. The best value of the integrated amplifier SNR should be greater than 90dB; radio head: FM stereo 50dB, in order to achieve more than 70dB is better; tape recording seat 56dB (common band), but after Dolby noise reduction signal noise The ratio has greatly improved. If the Dolby B noise reduction signal to noise ratio of up to 65dB, after Dolby C noise reduction, the signal to noise ratio of up to 72dB (above mean ordinary belt); CD machine's signal to noise ratio of up to 90dB or more, high-end The more up to l10dB. When the signal-to-noise ratio is low, the noise is severe when the small signal is input. The sound of the entire range of the notebook has a murmur and the turbidity is clearly unclear. Therefore, the speaker whose SNR is lower than 80dB is not recommended to buy! Subwoofer 70 Db subwoofer is not recommended for the same reason.

9, scalability

This refers to whether the speaker supports multi-channel simultaneous input, whether there is an output interface to the passive surround speakers, and whether there is a USB input function. The number of surround speakers that can be connected to the subwoofer is also one of the criteria for scaling performance.

10, sound technology

Hardware 3D sound technology is now more common SRS, APX, Spatializer 3D, Q-SOUND, Virtaul Dolby and Ymersion several, although they are implemented in different ways, but can make people feel a clear three-dimensional sound field effect, in which Again the former three are more common. Their application is extended stereo (Extended Stereo) theory, which is through the circuit for additional processing of the sound signal, so that the listener feels the sound image position extended to the outside of the two speakers, in order to expand the sound and image, so that people have space Sense and three-dimensional, resulting in a more spacious stereo effect. There are also two sound enhancement techniques: active electromechanical servo technology (essentially using the Helmholtz resonance principle), BBE high-definition monocular sound reproduction system technology speaker and "phase fax" technology, which also have an effect on improving sound quality. . For multimedia speakers, SRS and BBE are relatively easy to implement and can effectively improve the speaker's performance.

11. Tones

It refers to a signal that has a specific, usually stable, pitch, which is generally the degree to which the sound sounds tones. It depends mainly on frequency, but also with the intensity of the sound. The response of a human ear with a high frequency of sound is a tone with a high pitch and a low frequency of sound. The human ear responds with a low pitch. The tone is basically logarithmic with frequency (Hz). Different instruments play the same frequency notes, although the timbres are different, but their pitch is the same, that is, the fundamental frequency of the performance sound is the same.

12, sound

The sensation of sound quality is also a characteristic quality of a sound from another sound. When different instruments play the same pitch, their colors can be different. This is because their fundamental frequency is the same, but the harmonic components are very different. Therefore, the timbre depends not only on the fundamental frequency, but also closely related to the harmonics of the fundamental frequency to an integral multiple, which makes each mp3 download instrument and each person have different timbres.

13, stereo separation

The ability, degree, or degree of isolation, that the two channels do not interfere with each other, is usually expressed as the difference between the signal level in one channel and the level that leaks into another channel. If the stereo separation is poor, the three-dimensionality will be weakened. The minimum index of stereo separation degree specified by the International Electrotechnical Commission is greater than or equal to 40dB at lKHz, and it is better to achieve 60dB of large dry sound; the stereo separation degree of FM stereo broadcasts specified by the European Broadcasting Union is >25dB, which can actually achieve 40dB or more. . Stereo channel balance refers to the difference between left and right channel gains, which is generally expressed as the maximum difference between the left and right channel output levels. If the imbalance is too large, the stereo image position will deviate. The indicator should be less than 1dB.

14, damping coefficient

Refers to the ratio of the amplifier's rated load (speaker) impedance to the actual impedance of the power amplifier. A large damping coefficient indicates that the output impedance of the power amplifier is small, and the damping factor is the ability of the amplifier to control the speaker cone movement after the signal disappears. Amplifiers with a high car horn price damping factor act more like a short circuit for the speaker, reducing its vibration at the end of the signal. The output impedance of the power amplifier directly affects the low frequency Q of the speaker system, which affects the low frequency characteristics of the system. The Q value of the speaker system should not be too high, generally in the range of 0.5 ~ l is good, the output impedance of the power amplifier is the factor that makes the low frequency Q value rise, so generally it is desirable that the output impedance of the power amplifier is small, and the damping coefficient is great . The damping coefficient is generally between tens and hundreds, and the damping coefficient of a high-quality professional power amplifier can be as high as 200 or more.

L5, equal loudness control

Its role is to boost high and low frequency sounds at low volume. Due to the poor auditory sensitivity of the human ear to high-frequency sounds, especially low-frequency sounds, it is required to perform acoustic compensation for high frequencies and low frequencies at low volumes, that is, it requires a large increase in low frequencies and a certain increase in high frequencies. In other words, when the volume is reduced, the lower frequency portion of the signal is reduced in the higher frequency portion. Equal loudness control is to meet this requirement, and the equal loudness control is generally 8dB or 10dB.

16, three-dimensional sound field processing and looping speaker Robich complete sound

Why do common two speakers make us hear sounds that do not exist? It is known to all that stereoscopic movies are the illusions that the eyes produce and the three-dimensional sound field can not be created without the illusion of ears. Various hardware 3D sound effects technologies such as SRS, virtual Dolby, and software 3D technologies such as EAX, A3D, etc., are new technologies that have been thoroughly studied to reduce the cost after the human ear receives sound. In essence, the effect of using a multi-speaker to complete a three-dimensional sound field is much better than the virtual sound field of two speakers. Therefore, surround sound should be based on multiple speakers, and their sense of location and space are strong.

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