Speaker performance index

1. Frequency range (unit: Hz): refers to the range from the effective sound reproduction frequency to the high effective sound reproduction frequency. The reproducing frequency range of the speaker is ideal to reproduce the audible frequency range of the human ear evenly, that is, 20HZ~20000HZ. However, if you want to replay at a louder sound pressure level, the lower the frequency band, the larger the amplitude structure and the reduction of distortion are considered. Generally, the volume of the speaker needs to be increased. So the goal should not be too high, 50HZ~16KHZ is enough, of course, 40HZ~20KHZ is better.　　

2. Frequency response (unit: decibel dB): refers to the connection of a constant voltage output audio signal with 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 lag changes with the change of the frequency. The phenomenon that changes with frequency, the corresponding relationship between sound pressure and phase and frequency is called frequency response. The curve of sound pressure changing with frequency is called "amplitude-frequency characteristic", the curve of phase lag changing with frequency is called "phase-frequency characteristic", and the combination of the two is called "frequency response" or "frequency characteristic". The amount of change is expressed in decibels. This indicator is an important indicator for assessing the quality of speakers. The smaller the decibel value, the flatter the frequency response curve of the speaker and the smaller the distortion.　　

3. Directional frequency characteristics: The frequency response curve clusters of the speaker measured in the direction of a number of prescribed sound wave radiation, such as the 0 degree, 30 degree and 60 degree directions of the central axis of the speaker. For example, a sound box with good directivity is like a fluorescent lamp, and the light can be evenly distributed to every corner of the room. On the contrary, it is like a flashlight.　　

4. Large output sound pressure level: indicates the loud sound level index that the speaker can give when inputting high power.　　

5. Distortion (expressed as a percentage).　　Harmonic distortion refers to the addition of high-order harmonic components that are not in the original signal to the reproduced sound. Intermodulation distortion, we know that the speaker is a non-linear device. In the process of replaying the sound source, due to the non-uniformity of the magnetic field of the magnetic gap and the non-linear deformation factor of the supporting system, a new frequency that is not in the original signal will be generated. Component, so when the new frequency signal and the original frequency signal are added to the loudspeaker together, it will be modulated to produce another new frequency. In addition, the music signal is not a single-tone sine wave signal, but a multi-tone signal. When two signals of different frequencies are input to the speaker at the same time, due to the large amount of non-linear factors, the two signals will be modulated and a new frequency signal will be generated. Therefore, in addition to the original signal, there are two For new frequencies that are not in the original signal, this distortion is intermodulation distortion. Its main influence is pitch (also known as pitch).　　 Transient distortion, the transient distortion of the speaker system, refers to a kind of transmission waveform distortion caused by the mass inertia of the speaker vibration system. Due to the certain mass inertia of the loudspeaker, the cone vibration cannot keep up with the instantaneously changing electrical signal, which causes the distortion of the transmission waveform of the reproduced sound, which leads to the change of the frequency spectrum and the 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 tone reproduction.　　

6. Marked power (unit: watt W): The power marked on the speaker. There are two popular marking methods in the world: 　　 long-term power or rated power. The former refers to the input of a specified analog signal to the speaker within the rated frequency range, and the signal duration is 1 minute, 2 minutes interval, repeat 10 times, the speaker does not produce the maximum input power of thermal damage and mechanical damage. The latter refers to the input of a frontier sine wave signal to the speaker within the rated frequency range, the signal duration is 1 hour, the speaker does not produce the maximum sine power of thermal damage and mechanical damage.　　

The maximum withstand power is music power (MPO), which originated from the German Industrial Standard (DIN) and refers to the short-term maximum power that the speaker can withstand. This is because when the music signal is played, the amplitude of the audio signal changes greatly, and sometimes the peak value of the music power may exceed the rated power several times in a short time. The power labeling standards established by my country's national standard GB9396-88 include maximum noise power, long-term maximum power, short-term maximum power, and rated sine wave power. Usually speaker manufacturers use long-term power or rated power as the marked power of the speaker.　　

7. Nominal impedance (unit: ohm Ω): refers to the ratio of the signal voltage U to the signal current input by the speaker (this is the same as in high school physics, R=U/I). Because the impedance of the speaker is a function of frequency, the magnitude of the impedance value also changes with the frequency of the input signal. The preferred values of speaker impedance specified by my country's national standards are 4Ω, 8Ω, 16Ω (the recommended value of international standards is 8Ω), and the nominal impedance of the speaker is specified as: the lowest value between the peak value F0 of the speaker resonance frequency and the second resonance peak F1 Impedance value. Some foreign speaker manufacturers use a section where the impedance characteristic curve tends to be flat as the speaker's nominal impedance. The nominal impedance of the speaker is different from the nominal impedance of the speaker, because there is more than one speaker unit in the speaker, the nature of each unit is not the same, and there are series or parallel crossover networks, so the standard stipulates the lowest impedance Must not be less than 80% of the nominal impedance value.　

8. Sensitivity (unit: decibel dB): The sensitivity of the speaker is 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 (sound pressure and The amplitude of the sound wave is proportional to the frequency, and the sound pressure level is an indicator of the relative magnitude of the sound pressure). What needs to be particularly pointed out here is that although sensitivity is an indicator of speakers, it has nothing to do with sound quality and tone. It only affects the loudness of the speakers. You can increase the input power to increase the loudness of the speakers.　　

9. Efficiency (expressed as a percentage): The definition of speaker efficiency is the ratio of the sound power output by the speaker to the electric power input (that is, the percentage of sound-electric conversion). Recently, the speakers on the market are usually marked with sensitivity, while some speakers are marked with efficiency, but expressed in decibels. This wrong way of labeling has caused some consumers to confuse the two indicators of sensitivity and efficiency. The two indicators of speaker sensitivity and efficiency have nothing to do with sound quality and timbre, nor are they a standard for assessing quality. However, the sensitivity and efficiency are too low to increase the input power of the amplifier to achieve the required sound pressure level.