Understand Speaker Performance Indicators

- Jul 10, 2020-

Some friends tend to pay more attention to some surface indicators when buying speakers, such as whether the cabinet is all wood, whether the size of the speaker unit is ahead of the same level, etc. However, for the speaker, it can have excellent playback effects, external Factors are just one of the important factors. There are many invisible internal factors that also determine the quality of the speakers.


People who are a little more careful will notice that behind the speaker or in the manual, there is usually a technical indicator description, which usually includes the sensitivity, frequency range, carrying power and impedance of the speaker. Among them, sensitivity is the most important indicator of the speaker. It largely determines what kind of power amplifier the box should be equipped with, how much power is required to push, etc. These are internal factors that you cannot see.


Although these internal factors are invisible, they are audible. If we understand some knowledge related to this aspect, we can focus on these aspects when selecting or purchasing speakers. Although the manufacturers of these technical indicators may not be completely labeled accurately, at least they can give us a reference on the data, and also provide a basis for comparison when we actually choose the test speakers. What are the performance indicators of the speakers? Please follow the editor to take a look.


1. Power


1. Rated power


Rated power, that is, long-term power, means that long-term use in this power state will not damage. It refers to the power that the speaker does not damage without continuous distortion for more than 8 hours of continuous operation. This power is nominally of practical use value.


2. Carrying power


The carrying power of the speaker means "the input speaker will not be damaged if it exceeds this marked power, and it can withstand it". Refers to the average power of the signal applied to the input of the speaker under the condition that the speaker is allowed to have a certain distortion. The loudspeaker unit with larger power is not easy to be distorted by the high power provided by the power amplifier, and it can have a better performance when listening to burst music; and, the speaker needs to cooperate with the power amplifier to provide a larger sound pressure, and It is not to say that speakers with high carrying power must be "loud".


3. Peak power


   refers to the maximum power that the speaker can withstand in a short time. It refers to the largest strong pulse that the equipment can withstand within 1/100 second, that is, 10 milliseconds, and the equipment is not burned. This power is usually 4 times the rated power. The speaker's ability to withstand peak power is limited. The time setting is 1 second, and it can only be repeated 10 times. If it exceeds it, it may be damaged. Speakers marked with peak power should be used with extreme caution. It is recommended that the power should not exceed the peak value. 1/4 of the power.


Second, the signal to noise ratio


   Signal-to-noise ratio, or SNR

Noise Ratio, also known as the signal-to-noise ratio, is the ratio of the voltage of the output signal of the amplifier to the noise voltage output at the same time, often expressed in decibels. The higher the signal-to-noise ratio of the device, the less noise it produces. Generally speaking, the greater the signal-to-noise ratio, the lower the noise mixed in the signal, the higher the sound quality of the sound playback, otherwise the opposite. The signal-to-noise ratio should generally not be less than 70dB, and the signal-to-noise ratio of high-fidelity speakers should reach more than 110dB.


The signal-to-noise ratio is the ratio of the normal sound signal played back by the speaker to the noise signal (power) when there is no signal. Expressed in dB. For example, the signal-to-noise ratio of a speaker is 80dB, that is, the output signal power is 80dB greater than the noise power. The higher the signal-to-noise ratio value, the smaller the noise. In order to ensure the sound effect, it is recommended that speakers with a signal-to-noise ratio of more than 80dB can be included in the purchase.


3. Frequency response


The frequency response range of the speaker refers to the frequency response width of the speaker under the rated power state and within the specified amplitude variation range when the audio signal is replayed. In layman's terms, it is the range between the lowest and highest sound that the speaker can emit. Generally speaking, under specified power conditions, the gains at the high and low ends of the frequency drop by -3dB, respectively. The bandwidth between the two points is called the frequency response range of the amplifier.


This indicator reflects the main frequency range of speaker operation. The wider the range, the better the sound characteristics (under the same conditions as other related indicators). The range that human hearing can reach is about 20Hz-20KHz. Within the rated frequency range, the ratio of the maximum value to the minimum value of the output voltage amplitude is expressed in decibels (dB). People with sounds below 20Hz can hardly feel it through their ears, they can only feel it through other organs.


4. Sensitivity


   Sensitivity refers to the sound pressure level measured at 1m in the axial direction when the speaker is added with a pink noise signal voltage equivalent to 1W of power at the rated impedance. The sensitivity of a speaker determines whether the speaker is efficient. Speakers with high sensitivity can save the output power of the power amplifier under the same sound pressure level, and vice versa. The low-frequency response of high-sensitivity speakers is relatively poor, and the low-sensitivity speakers consume power and the low-frequency response is better.


5. Distortion


The concept of speaker distortion and amplifier distortion is basically the same, except that the amplifier input is an electrical signal, and the output is still an electrical signal, and the speaker input is an electrical signal, and the output is an acoustic wave signal, so the distortion level of the speaker is the The amount of distortion that occurs when converting between a signal and a sound signal. The distortion level index is only a relatively general statement, which should be divided into three types: harmonic distortion, mutual distortion and transient distortion.


Harmonic distortion refers to the distortion caused by the addition of higher harmonic components that are not in the original signal during sound playback: Intermodulation distortion mainly affects the tone of the sound: Transient distortion is because the speaker has a certain inertial quality. The vibration of the basin cannot keep up with the vibration of the instantaneously changing electrical signal, which results in the difference between the original signal and the playback sound. It is a very important indicator in the speaker and speaker system, which directly affects the degree of restoration of sound quality and timbre, so this indicator is closely related to the quality of the speaker. Usually expressed as a percentage, the smaller the value, the smaller the distortion. The distortion of ordinary multimedia speakers should be less than 0.5%, while the distortion of subwoofers is generally large, less than 5% is acceptable.


6. Impedance


   This indicator represents the ratio of the voltage and current of the speaker speaker input signal. There are many types of input impedance of speakers. Generally speaking, the impedance greater than 16Ω is high impedance, and the impedance lower than 8Ω is low impedance. The standard impedance of the speaker is 8Ω. In the case of the same power amplifier and output power, the low impedance speaker can get more Large output power, but the impedance is too low will cause underdamping 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 8Ω. The impedance of headphones is generally high impedance-32Ω is very common. The impedance of the power amplifier can generally be marked as equivalent impedance, such as the output of 130W at 4Ω, which is roughly equivalent to the output of the equivalent 8Ω80W, which is not good if it is large or small. The input impedance of the speaker should match the output impedance of the amplifier. If it refers to the input impedance of the power amplifier, it should be a little higher, which helps to improve the anti-interference ability of the system.


7. crossover point


   Crossover point refers to the dividing point between the high-pass, band-pass and low-pass filters of the frequency divider, which is usually expressed by the frequency and the unit is Hertz. The high and low frequency two-way speakers have only one crossover point, and the high, middle and low three-way speakers have two crossover points. The crossover points should be determined according to the frequency characteristics and power allocation of the speaker unit or speaker in each frequency band.


The crossover point is a mark of the frequency response range assigned to each speaker unit by the frequency divider, and is determined according to the audio performance capability of the speaker unit (boundary frequency determined by the effective diameter of the unit diaphragm); for example, high frequency units and The crossover point of the intermediate frequency unit is usually 3000Hz~4000Hz, the crossover point of the intermediate frequency unit and the low frequency unit is usually about 400Hz, and the crossover point of the subwoofer unit is usually 150Hz or lower.


The more crossover points of a speaker prove that the audio performance range of the speaker is larger, and the more speaker units are. It is easy to make a speaker, but difficult to make a good speaker, especially for a three-way frequency or more, and the quality of the crossover has become the main indicator of whether the speaker is on the high grade under the premise of high quality of the speaker unit. , Good frequency divider strives for precision, endless art. In the case of three-way frequency division, the farther the two crossover points should be separated (should be more than three octave bands), the better the combined system response will be.