Audio Knowledge Complete Manual 1, the acoustic speaker is a device that restores the electrical signal into sound signal, and the restore authenticity will be an important criterion for evaluating speaker performance. Active speaker is a speaker system with a power amplifier (ie, the power). Integrate the power amplifier and speaker vocal system, you can directly match the general sound source (such as a follow-up, CD machine, VCD machine, video recorder, etc.), constitute a complete set of sound combinations. With an active speaker, there is no need to purchase a power amplifier, no longer a reasonable optional power amplifier, the speaker is worried, the operation is simple, its performance price ratio, is generally accepted for the work class. According to the principle of vocalization and internal structure, the speaker can be divided into inverted, closed, flat, horn, labyrinth, etc., the most important form is closed and inverted. The closed speaker is loaded on the closed casing, the efficiency is relatively low; and the inverted speaker is different from it to the front or rear panel. It works according to the principle of the Herm Hholz resonator, the advantage is that the sensitivity is high, and the power can be affected and has a wide dynamic range. Because the sound waves behind the speaker must be released from the guided hole, it is also higher than the confidential box. Moreover, the same speaker is equipped with a low-frequency sound pressure obtained in the suitable inverted box in a suitable inverted box, which is good for the performance of the low frequency part, so this is also a widespread case. Popularization cause.
2, power
The quality of the sound quality of the speaker is not directly related. The power determined is the most sound that the speaker can make, and it feels how much the sound emitted by the speaker can be. According to international standards, there are two labeling methods: rated power (RMS: sine wave average square root) and instantaneous peak power (PMPO power). The former refers to driving an 8Ω speaker within a rated range specifies that the waveform continuous analog signal is there, and after a certain number of times and repeats a certain number of times, the speaker does not have any damage to the maximum electric power; the latter refers to the maximum power that the speaker can withstand. . The US Federal Trade Commission specified the power of the power to determine the power of power in 1974: driving an 8Ω speaker load in two channels, and the number of effective watts measured when harmonic distortion in the 20-20000Hz range, that is, the amplifier Output power, its indication power is the rated output power. Usually the merchant lays an instant (peak) power in order to cater to consumer psychology, generally 8 times the rated power. Imagine the use of Philips's TDA1521 amplifier chip (maximum rated power 30W, THD = 10%), and some products nominally 360W, or even 480wp.mpo, can this possible? Is it meaningful? So in the purchase multimedia The speaker should be based on rated power. The power of the speaker is primarily decided by both the power amplifier chip and the power of the power transformer. Considering other factors, it can be calculated that if the rated power of the transformer is 100W, it actually can smoothly drive the power amplifier chip's power to 45W or less. Therefore, the actual rated power of the speaker can reach the nominal value by calculating the power relationship of the speaker transformer and the amplifier. The power of the speaker is not bigger, the better, the application is the best, for the 20 square meters of ordinary home users, the true 60W power (the effective output power 30W × 2) of the speech is sufficient, but The larger the power amplifier, the better, preferably more than 2 times the actual output power. For example, the ability of the speaker output is 30W, the power of the power is preferably greater than 60W. For the HIFI system, the power amplifier power drives the speaker is very large.
3, frequency range and frequency response
The former is the scope of the minimum effective playback frequency and the highest effective playback frequency that can be played back; the latter means the sound pressure generated by the sound voltage output with the system, the sound pressure generated by the speaker Increase or attenuate, the phase varies with frequencies, and the correlation between the correlation between the sound pressure and phase and the frequency is referred to as frequency response, and the unit decibels (DB).
The frequency characteristics of the audio system often use the longitudinal coordinates of the decibel scale representation power and the frequency response curve indicating the frequency of the alignment scale. This power point is called a frequency response high frequency cutout point and a low frequency cut-off point of the frequency response when the sound power is 3dB lower than the normal power. The frequency between the high frequency cutoff and the low frequency cutout point is the frequency response of the device; the curve of the sound pressure and the phase hysteresis is called "amplitude frequency characteristics" and "phase frequency characteristics", a syndrome "frequency, respectively. characteristic". This is an important indicator of the performance and price of speakers. It has a direct relationship with the performance and price of the speaker. The more the score value is, the more flat curve of the speaker, the smaller the distortion, the higher the performance. Such as: a speaker frequency is 60Hz to 18kHz /- 3dB. These two concepts sometimes do not distinguish, they are called the sound. In theory, the frequency response of 20 to 20000 Hz is sufficient. The sound below 20 Hz, although the other sensory organs can be observed, that is, it can feel the so-called bass, so in order to perfectly play various musical instruments and language signals, the amplifier should achieve high-fidelity goals. Play the harmonics of the tone. Therefore, the frequency band of the amplifier should be extended, the lower limit extends below 20 Hz, and the upper limit should be increased to more than 20,000 Hz. A representation of the frequency response of the source (radiograph, recording seat and laser player, etc.) is different. For example, the frequency response of the FM stereo broadcast specified in the European Broadcasting Union is 40 ~ 15000 Hz Ten / -2dB. The International Electrotechnical Council's lowest indicators specified in the recording seat: 40 ~ 12500Hz Ten /-2 /-2 /-2. 5dB (ordinary belt), the actual indicators that can be achieved are significantly higher than this value. The frequency response of the CD machine is 20000Hz, and the low frequency end can be low, only a few Hertz, which is one of the reasons why the CD machine is good.
However, the harmonic component constituting the sound is very complicated, and the wider sound of the non-frequency range is good, but this is basically correct for medium and low-grade multimedia speakers. In the label frequency response, we usually see two nouns with "System Sign" and "Amplifier". To know "System Sign", it is always smaller than the "amplifier frequency". "Amplifier Surround" has no significance, which is only used to deceive some uninformed consumers. The current speaker manufacturer is too large for the system, and the high frequency part is not a lot, but in the extremely unreal of the low-end, the foreign brand HIFI (high-protection) speaker is not marked 4, 50 Hz And the domestic two or three hundred wooden ordinary speakers actually dare to maribe this data, it is really a smile! Therefore, you will be able to listen to true low frequency bands, do not easily believe in the value on the leaflet. Music in multimedia speakers is based on music, songs, game sounds, background music, and vital sounds in MP3 or CDs, and these sounds are more high-volume, so when choosing multimedia speakers. It should be more read in the performance of its high-band sound, not a low frequency band. If you really pursue the theater effect, then a strong subwoofer will definitely meet your needs.
4, loudness
The strong sound is called intensity, which is determined by a rapidly changing amplitude (sound pressure) size. However, the actual actual strength of the human ear is inconsistent with the objective actual strength. People have called the strong sense of weight, and their measurement units are decibels (DB), which is based on the sound of 1000 Hz in different strengths. The ratio of the pressure ratio is taken from L / 10 of its common log value. The reason for the value of the value is due to the increase in intensity and loudness is not a proportional relationship, but the relationship between the true numbers and logs! For example, when the intensity of the sound is large, he sounds in the first stage (10dB), and the intensity is large to 100 times, it sounds two (20dB). For the sound signal of 1000 Hz, the lowest sound pressure of the human ear feels is 2 × 10E-5PA, which is set to 0 dB, and the human ear will not endure when the sound pressure exceeds 130 dB, and the dynamic range of the human ear is 0 ~ 130dB. People feel different from the intensity, the frequency of different sounds is different; the higher the sound pressure level, the more normal the human hearing frequency characteristics; the lower the sound pressure level, the smaller the human hearing frequency range; frequency f <16 ~ 20 Hz and F > 18 ~ 20kHz sound, regardless of how high the sound level, people can't hear. Therefore, the hearing frequency of the human ear is 20Hz to 20kHz. This frequency band is called audio or audio; regardless of the high sound pressure, the human ear is most sensitive to 3kHz ~ 5kHz frequencies.
Most people feel that the signal sound level mutation is 3dB below 3dB, so that the sound system is often a range of frequency response curves for the allowable frequency response curve.
5, distortion
Harmonic distortion, intermodulation distortion, and transient distortion. Harmonic distortion means distortion caused by increasing the high-end harmonic components of the original signal in sound playback; the intermodulation distortion affects the tone of sound; transient distortion is because the speaker has certain inertial quality, The vibration of the basin cannot keep the vibration of the instantaneous changes in the vibration of the electrical signal, and the difference between the original signal and the return tone. It is more important in the speaker and speaker system, directly affecting the degree of recovery of sound quality, so this indicator is closely related to the quality of the speaker. This is often expressed in a percentage, the smaller the value, the smaller the distortion. The distortion of ordinary multimedia speakers should be less than 0.5%, and usually the low-tech gilry is generally large, less than 5% can be accepted.
6, the sensitivity of the speaker (unit DB)
The sensitivity of the speaker is 3dB, and the output is doubled, generally in 87 dB is medium sensitivity, 84 dB or less is low sensitivity, and 90 dB is high sensitivity. The increase in sensitivity is at the expense of increasing distortion, so as a high-fidelity speaker, it is necessary to ensure that the degree of recovery of the tone must reduce the requirements of sensitivity. But can't, in turn, the sound quality of the sensitivity is not good, and the low sensitivity speaker must be good. The speaker amplifier of low sensitivity is difficult to promote (the storage power of the amplifier is required). So, although the sensitivity is an indicator of the speaker, it has nothing to do with the sound quality sound of the speaker.
7, impedance
It refers to the ratio of the voltage and current of the speaker input signal. The input impedance of the speaker is generally divided into high impedance and low impedance, higher than 16Ω, high impedance, lower than 8Ω is low impedance, and the standard impedance of the speaker is 8Ω. In the case where the amplifier is the same as the output power, the low impedance speaker can obtain a large output power, but the impedance is too low, which will cause undecimated damping and bass deterioration. 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 8Ω. The impedance of the headphones is generally high-impedance -32Ω very common. The impedance of the amplifier is generally standardable as an equivalent impedance, such as the output of 4Ω 130W, is approximately 80W of the equivalent 80W. There is a noun that is easy and confused is called "damping factor", which means that the speaker impedance divided by the amplifier source, the range is approximately 25 ~ 1000. The speaker paper pot is still oscillating many times after the electrical signal has disappeared, and the current and magnetic field generated by the coil can prevent this parasitic movement, which is damping. The amplitude of the current is the effect of damping depends on the internal resistance of the amplifier output stage. This resistor is much lower than the rated impedance of the speaker, typically 0.1 Ω, but due to the series resistance and divide of the speaker voice coil. The existence of series resistance of the network, the damping coefficient is difficult to do 50.8, signal-to-noise ratio
It is the ratio of the normal sound signal (power) when the tester is played back and the noise signal (power) when there is no signal. Also represented by DB. For example, a signal to noise ratio of a tape recording holder is 50 dB, i.e., the output signal power is 50 dB than the noise power. The higher the signal to noise ratio, the smaller the noise. The minimum requirement of the International Electrotechnical Commission's signal-to-noise ratio is that the preamplifier is greater than or equal to 63dB, and the post-level amplifier is greater than or equal to 86dB, and the merged amplifier is greater than or equal to 63dB. The optimum value of the merged amplifier signal-to-noise ratio should be greater than 90dB; the radio: 50dB of FM stereo, actually achieves more than 70dB or more; 56dB of tape recording seat (ordinary belt), but by Dolby noise It is greatly improved. If the noise ratio of Doli B is 65dB, it is more than 72dB after Dolby C noise reduction, it can reach 72dB (all the above refers to ordinary belts); the signal-to-noise ratio of the CD machine can reach 90dB, high-end More than L10DB or more. When the signal-to-noise ratio is low, the small signal is input, and the sound of the entire zono is clearly feeling is turbid, so the signal-to-noise ratio is less than 80 dB speakers are not recommended! The subwoofer 70 dB of the subwoofer is not recommended for purchase.
9, speakers
The low-grade plastic speaker cannot overcome resonance because of its case, no sound quality, no sound quality (stupid, not, designing good plastic speakers are much better than inferior wooden speakers); wooden speakers reduce box resonance The contracted sound is generally better than plastic speakers. Usually the multimedia speakers are two-point design, a smaller speaker is responsible for the output of the medium and treble, and the other larger speaker is responsible for the output of the medium. Picking speakers should consider these two speakers: multimedia active speakers are now mainly based on soft ball top (in addition to titanium film tops for simulating source), it can reduce high frequency with digital sound source The signal of the signal is given to people with gentle, smooth, delicate feelings. Multimedia speakers are now with soft spheres such as silk film and low cost PV membranes. The bass unit determines the characteristics of the sound of the speaker. It is relatively important, the most common there are the following: paper pots, there are several kinds of paper-based paper pots, paper-based sheep, tight press, paper pot sound Natural, cheap, better rigidity, high material is high, and the disadvantage is that the moisture-proof sex is poor, and the consistency consistency is difficult to control. However, it is everybody in the top HIFI system, because the sound output is very average, and the restore is good Anti-blocking, has a wide range of frequently and low distortions, is the preferred choice for a strong bass, the disadvantage is that the cost is complex, the production process is complex, the sensitivity is not high, the musical effect is not good; wool woven pots, soft texture, It is very excellent in soft music and light music, but the bass effect is poor, lacks strength and shocking; PP (polypropylene) pot, it is widely traveled in high-grade speakers, consistency is good, and all aspects can be circled Society. In addition, there is no discussion because of the low price of the fiber diaphragm and composite diaphragm. The speaker size is naturally, the bigger the better, the low-caliber whispering speaker can have a better performance at the low frequency section, which is available in the purchase. Speakers manufactured with high performance speakers mean lower transient distortion and better sound quality. Ordinary multimedia speakers low speakers are between 3 to 5 inches. Speakers manufactured with high performance speakers also means having lower transient distortion and better sound quality. 10. Structure and characteristics of speakers
The speaker can be divided into bookshelf and floor-standing. The former is small, the level is clear, the positioning is accurate, but the power is limited, the extension of the low frequency band is insufficient, suitable for appreciation of high-fidelity music-based music hobby It is also the first choice for our multimedia enthusiasts; the latter is large, withstand power is also large, the low frequency is strong, good at expressing the momentum and powerful power, but doing unhappy and positioning aspects Will be slightly lacking. For lovers of different music, this is also an important part of the purchase of the previous purchase. Since the PC is rarely available, the compact desktop bookcase should be the first choice for multimedia active speakers. In general: As long as the power amplifier module is designed reasonable, the larger the box, the larger the speaker, the more the sound is listening. 11. Scalability This is whether a speaker supports multi-channel simultaneous input, whether there is an output interface of the passive surround speaker, whether there is a USB input function. The number of subwoofer can be external to the speaker is also one of the standards that measures the expansion performance. The interface of ordinary multimedia speakers mainly has two kinds of analog interfaces and USB interfaces. Other digital interfaces such as fiber interfaces, and the digital interface, etc., so there is not much introduction.
12, sound technology
Hardware 3D sound technology is now more common with SRS, APX, Spatializer 3D, Q-Sound, Virtaul Dolby, and Ymersion, etc., although each implementation is different, but people can feel obvious three-dimensional sound field effects, of which It has been more common in the past. They are all extensive stereo theory, which is an additional process to the sound signal through the circuit, so that the listener feels that the sound image is extended to the outside of the two speakers, so that the sound spread, makes people have space Feeling and three-dimensional effects produce a more wide stereo effect. There are also two kinds of sound enhancement techniques: active electromechanical servo technology (essentially utilized Hermbhet resonance principle), BBE high-definition plateau audio-reproducing system technology and "phase fax" technology, there is a certain effect on improving sound quality. For multimedia speakers, both SRS and BBE are more likely to achieve good effect, which can effectively improve the performance of the speaker. 13, tone
Refers to a signal having a specific and typically stable tone, and a popular saying is the degree of sound listening to the degree of toning. It mainly depends on the frequency and is related to the intensity of the sound. The reaction of high frequency of frequency is that the reaction of high tone is high and the frequency of frequency is low, and the tone is low. The change in tones is substantially a logarithmic relationship. Different instruments play the same frequency note, although the sound is different, but their tones are the same, that is, the base frequency of playing sounds is the same.
14, tone
The sensation of sound quality is also a characteristic quality of the sound difference in another sound. Different instruments are in the same tone, they can be different. This is because their base frequency frequencies are the same, but the harmonic component is very different. Therefore, tone is not only dependent on the base frequency, but also is closely related to the harmonics of the fundamental frequency, which makes each instrument and each person has a different tone.
15, dynamic range
The strongest and weakest ratio in the sound, represented by DB. For example, a band's dynamic range is 90dB, which means the weakest portion of the power than 90 dB of the most resounded portion. The dynamic range is the ratio of power, and is independent of the absolute level of the sound. As mentioned earlier, the dynamic range of human vesicles ranges from 0 to 130 dB. The dynamic range of various sounds in nature is also very large. The general language signal is approximately 20 ~ 45dB, and some symphony has a dynamic range of 30 to 130 dB or higher. However, due to some factors, the dynamic range of the sound system is rarely reached the dynamic range of the band. The intrinsic noise of the recording device determines the maximum sounds of possible recording, and the maximum signal capacity of the system (distortion level) limits the strongest sound. Generally, the dynamic range of the sound signal is set to 100 dB, so the dynamic range of the sound device can do 100 dB, it is very good.
16, Total Harmony Distortion (THD)
When the audio signal source is passed through the power amplifier, the output signal caused by the nonlinear element is more than the additional harmonic component than the input signal. Harmonic distortion is due to the system is not completely linear, and we are expressed in the percentage of roots and original signal valid values with newly increased total harmonic components. For example, an amplifier adds LV 2000 Hz when the output 10V is 1000 Hz, and there is 10% second harmonic distortion. All additional harmonic levels are referred to as total harmonic distortion. Generally, the total harmonic distortion at 1000 Hz frequency is the smallest, so many products are distorted by this frequency as its indicator. However, the total harmonic distortion is related, so the US Federal Trade Commission has stipulated in 1974 that the total harmonic distortion must be measured over the full audio range of 20-20000Hz, and the maximum power of the amplifier must be loaded as 8 euro speakers, always Harmonic distortion is measured under conditions of 1%. The total harmonic distortion of the International Electrotechnical Commission is: the pre-premium amplifier is 0.5%, the merge amplifier is less than or equal to 0.7%, but it can actually be 0.1%: FM stereo tuner is less than or equal to 1.5%, actually It can be 0.5% or less; the laser player can make 0.01% or less. Since the current method of measurement distortion is a single sine wave, the entire appearance of the amplifier cannot be reflected. The actual music signal is a different composite wave, including dynamic indicators such as rate conversion, transient response. Therefore, high-quality amplifiers sometimes indicate intermodulation, transient distortion, transient intermodulation distortion and other parameters. (L) Intermodulation Distortion (IMD): Transfer 125Hz and LKHZ of the interpretator, input to the measured amplifier, and measured intermodulation from the rated load at the amplitude of 4: 1 to the measured amplifier Distortion factor. (2) Transient Distortion (TIM): After inputting the square wave signal to the amplifier, its output waveform envelope will be expressed. If the conversion rate of the amplifier is not enough, the square wave signal generates a deformation, and transient distortion is generated. Mainly reflected in the fast music mutation signal, such as a striking instrument, piano, xylophone, etc., if the transient distortion is large, the crisp music will become a mixed. (3) Transient intermodulation distortion: Mix 3.15 kHz square wave signal and 15kHz sine wave signals are mixed by peak amplitude than 4: 1, after amplifiers, newly increased all intermodulated detrimental product valid values and original sinusoidal amplitude percentage. If the amplifier adopts the depth of the loop, the transient intermodulation is generally large, and the specific reflection of the sound is sluggish, blunt, and there is no feeling; the sound is smooth, delicate, natural. 17, stereo separation
Refers to the ability to interfere with each other between the two channels, that is, the degree of isolation, that is, the difference in the level of signal levels in a channel and the leakage to the other channel. If the stereo separation is poor, the three-dimensional sensation will be weakened. The minimum indicator of the stereo separation of the International Electrotechnical Commission, LKHz is greater than or equal to 40 dB, actually reaching the big dry 60DB is good; the stereo separation of the FM stereo broadcast specified by the European Broadcasting Union is> 25dB, in fact, can do more than 40dB or more . The three-dimensional channel balance refers to the difference in left and right channel gains, generally in the maximum difference between the left and right channel output levels. If the imbalance is too large, the stereo sound position will be deviated, and the indicator should be less than 1 dB.
18, damping coefficient
It means the ratio of the rated load (speaker) impedance and power amplifier actual impedance. The damping coefficient represents a small output resistance of the power amplifier, the damping coefficient is the ability of the amplifier to control the movement of the speaker cone after the signal disappears. A amplifier with high damping coefficients, more like a short circuit for the speaker, which can reduce its vibration when the signal is terminated. The output impedance of the power amplifier directly affects the low frequency Q value 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. It is generally better in the range of 0.5 to 1, and the output impedance of the power amplifier is a factor that increases the low frequency Q value. Therefore, it is generally desirable that the output impedance of the power amplifier is small, and the damping coefficient is very good. . The damping coefficient is generally between tens to hundreds, and the damping coefficient of high quality professional power amplifiers can be up to 200 or more. L9, equal loudness control
Its role is to increase high frequency and low frequency when low volume. Because the human ear is high frequency, especially low-frequency auditory sensitivity, requires hearing compensation for high frequency and low frequencies when the low frequency is required, that is, the low frequency is increased, and there is a certain amount of increase in high frequency. In other words, when the volume is reduced, the reduction in the low frequency portion in the signal is less than the high frequency portion. The equal loudness control is satisfied, and the equal loudness control is generally 8dB or 10 dB.
20, 3D sound field processing and surround sound
Why does the ordinary two speakers have made us not to have the sound of the sound? Everyone knows that the stereo movie is the illusion of the eye and the generation of the three-dimensional sound field is inseparable. Various hardware 3D sound technologies such as SRS, virtual Dolby and software 3D technology such as EAX, A3D, etc. It is to fully study the new technologies launched by the human ear receive the sound of the sound. Essentially, the effect of completing the three-dimensional sound field through multi-speaker is much better than the sound field virtually in the two speakers. Therefore, surround sound should be dominated by multi-speaker configuration, their positioning sense and space is strong, let's take a look at what kind of real surround sound:
A Dolby Pro-Logic Surround System 4-2-4 Coding Technology The audio information of the left, middle, right, and rear sides is recorded in the left and right channels; when the play is By decomposing the four channels from the left and right channels, the four channels are often referred to as: front left channel, front intermediate channel, front right channel and rear surround channel . Scientific experiments have shown that it is necessary to gain the real sound effect of the immersive, must have a four-sided sound field environment around the listener, the more the number of channels used throughout the sound system, the more strong the listener's voice field is, the stronger, The more realistic feelings in the impetus. Based on the audiovisual environment of the currently home, the sound system uses 5 channels that can meet the positioning needs of the sound field, so Du Bocetable logic surround sound systems use 5 channels. From the surface, the 5-channel Dolby orientation logic surround sound power amplifier does have 5 power output: front left channel, medium channel, front right channel, surround left channel (also known as later Left channels) and surround right channels (also known as back right channels), but the surround sound signal output from the Du Bi-directional logic surround the sound system is actually a mono, 5-channel power amplifier Two surround channels are inner and amplifier in the amplifier and the speaker matching four elements amplifier and speaker collation pay attention to the warm and warm and warm, so that the complete equipment restore sound is neutral, which is only considered from art. However, the elements considered from the technology are:
I. Power matching two, power reserve matches three, impedance matching four, the matching factor match If we recognize the above four points, the performance of the equipment can be maximized and most played. Power match In order to achieve high-fidelity listening requirements, the rated power should be determined according to the best listening sound pressure. We all have this feeling: the volume hours, the sound is weak, single, dynamic, no shiny, low frequency is lacking, fullness difference, the sound seems to be inside. When the volume is suitable, the sound is natural, clear, round, soft, powerful, dynamic. However, when the volume is too large, the sound is hard to be soft, rough, and there is a feeling of tiedrally. Therefore, the playback sound pressure level is a large relationship with the sound quality. It is specified that the sound pressure level of the audio area is preferably 80 to 85 dB (A), we can calculate from the audio area to the speaker's distance to the characteristics sensitivity of the speaker. The rated power of the speaker and the rated power of the amplifier. Power reserve matching speaker: In order to allow it to be damaged or distortion in order to withstand the impact of burst strong pulses in the program signal. Here is an empirical value for reference: the selected speaker nominal rated power should be three times that of the manager calculation. Amplifier: The power reserve required is different compared to the electrical power amplifier and transistor amplifier. This is because the ultraload curve of the electronic pipe power is relatively gentle. The peak of the exhaustive music signal is not obviously incorrectly generated, but the peak tip is turned around. This is the flexible shear of us often said. After the transistor is placed in the over-pending point, the nonlinear distortion increases rapidly, and the signal generates a severity clipper, which is not a peak round but cut it allocate it. There is a composite impedance analog speaker consisting of resistance, inductance, and capacitance, a test of several high-quality transistor power amplifiers. The results show that in the case where there is a phase shift, there is a power amplifier that nominal 100W, and the actual output power is only 5W when the distortion is 1%! From this to the reserve amount of transistor amplifier: 10 times the civilian high-end amplifier: 6 ~ 7 times civil engine amplifier: 3 to 4 times, the electronic management power release can be larger than the above ratio. How much than the average sound pressure level and the maximum sound pressure level should be left, and the content of the program is set, the work environment is determined. This redundancy is 10dB, for modern popular music, Di Di, etc., there is a need to stay 20 ~ 25DB redundancy, so that the sound system is safe and stably. Impedance Matching It refers to the rated output impedance of the power and the rated impedance of the speaker should be consistent with the rated impedance of the speaker. At this time, the amplifier is in the optimal design load line, so you can give the maximum lossless power. If the rated impedance of the speaker is greater than the rated output impedance of the amplifier, the actual output power of the amplifier will be less than the rated output power. If the rated impedance of the speaker is less than the rated output impedance of the power amplifier, the sound system can work, but the danger of amplifier is overloaded, requiring a perfect overcurrent protection measures to solve, and the impedance matching requirements for electronic management power are more stringent. The matching damping coefficient kd of damping coefficient is defined as: kd = amplifier rated output impedance (equal to speaker rated impedance) / amplifier output internal resistance. Since the power amplifier output internal resistance has actually become the electric resistance device of the speaker, the KD value determines the resistance of the speaker. The larger the KD value, the higher the resistance, and the Kd value of the power amplifier is not, the better, the KD value will make the speaker electrical resistance, so that the pulse front is set up, reducing transient response indicators. Therefore, the large Kd value should not be pursued when the power amplifier is selected. As a household high-fidelity real power damping coefficient, there is an empirical value for reference, minimum requirements: The transistor amplifier is greater than or equal to 40, and the electronic tube power amplifier is greater than or equal to 6.
To ensure the basic conditions of the steady state characteristics of the play, the basic conditions of the transient characteristics should pay attention to the cooperation of the equivalent quality factors (QM) of the speaker and the amplifier damping coefficient (KD), which requires the feeder of the speaker as a sound system Part of a part of it. The equivalent resistance of the feeder of the speaker should be small enough, and it can be ignored compared to the rated impedance of the speaker. In fact, the power loss of the speaker feeder should be less than 0.5 dB (about 12%) to achieve this cooperation. Audio power amplifier is a field that has been quite mature. For decades, people have made unremitting efforts, regardless of line technology or components, and even think of great progress. Looking back on the development of the power amplifier, it may be a fun thing for our vast audio enthusiasts. Index: 1. Early transistor power amplifier two, transistor amplifier development and intermodulation distortion three, amplifier input stage - differential and total-centron four, amplifier power supply and A amplifier 5, other types of amplifiers
1. Advances in the early transistor amplifier semiconductor technology make transistor amplifiers into a big step forward. Since there is a transistor, people have started with its power amplifier. Early amplifiers were almost all use of ruthenium, but due to some causes of germanium, the transistors used in the amplifier, especially the active amplifier performance index, for example, the common-emitter cutoff frequency fH The value is 4kHz, the pressure resistance value of the large current pipe is generally around 30V. Thus, the frequency response of the amplifier is narrow, and its 3dB cutoff frequency is usually around 10kHz, which greatly affects the reproduction of high frequency signals in music. Adding three indicators of the power vessels, current, and power consumption interacts, making large power OTL or OCL amplifiers are not easy to find three indicators to meet the requirements of the requirements, so that the transformer coupled output should be used. The phase shift of the transformer has made it difficult to add deep negative feedback in the circuit, and the harmonic distortion is not sufficiently suppressed, so the tube amplifier in this period is very poor. "Still the aspiration", this kind of view is caused. Second, the development and intermodulation distortion of transistor amplifier With the gradual maturity of the semiconductor process, the large current, high-pressure transistor varieties are increasing, and more and more power amplifiers use an OCL circuit or OTL circuit that does not output transformers (Figure One). The initial high-power PNP tube is a germanium, and the NPN tube is a silicon tube. The difference between the two is very significant. The symmetry of the circuit is very poor. More than the quasi-complementary circuit shown in Fig. 2, through small power The silicon tube Q1 is compounded with a high-power NPN silicon tube Q2 to obtain a high power tube similar to the PNP tube, which reduces the distortion of the circuit due to the difference of symmetry. In the end of the 1960s, the complementary symmetry circuit was widely used in the end of the 1960s. The advancement of the component makes the technical index of the transistor power amplifier have a quality leap in terms of subjective sound quality, and it has also changed the views of the transistor amplifier in the past. Whether it is in the hall, the radio program is produced, the transistor The amplifier has been used in a large number, and the first time in quantity exceeds the electronic management power. In the commercially cultivated transistor megaphone, some destroyed cranes, such as JBL SA600, MARANTZ complementary symmetry circuit Model15, and the like. Although the advocate of the tube is still existed, people can look forward to the transistor amplifier relatively fairly. It is believed that the transistor machine is wide, the level is delicate, and there is a unique hatred with the electronic pipe machine, not a simple who replaces who problem. Transient intermodulation distortion is the first leap in the 1970s, and there is a most striking thing in the history of power amplifiers, which is transient intermodulated distortion and its measurement method. put forward. In 1963, an engineer of the Finnish Helvar factory was made by the wiring mistake, but it was very good to find the sound quality after the negative refueling decreased, and the objective technical indicators were unexpectedly found. Difference, while correcting the error, the technical indicator is improved, and the sound quality is significantly reduced. This phenomenon has attracted the attention of Mr. Otala at that time, after which he carried out this studies, first published Detin, first published the paper on transient power amplifier transient intermodulation distortion (TIM). By 1971, Dr. Otala and its research team had more than 20 papers published by TIM distortion theory, causing a wide range of resounds in electroacupuncture and complementary circuits.
Transient intermodulation is true to be like this: in direct coupling transistor amplifying circuits, in order to obtain small harmonic distortion and wide flat frequency response, the overall circuit is usually applied to a total of 40 dB of 60 dB of negative feedback, If the open loop distortion of the amplifier before the agglomeration feedback is 10%, then the distortion is reduced to 0.1% after the negative feedback of 40 dB, which is difficult to do. Transistor power is applied to 40 dB. 60DB negative feedback, so a gain requires 26dB amplifier, its open loop gain is 66,86db. Under such high gains introduce depth negative feedback, the circuit is bound to generate self-excitation, and thus the phase compensation is required, and it is generally connected between the collector-base poles of the promotion stage transistor, and disrupted the self-excitation oscillation. The phase condition forms a so-called "hysteresis compensation". When the amplifier input inputs a transition pulse that the duration is very short, since the capacitor C requires a charging time, the pushing tube collecting electrode voltage should be maintained for a period of time delay. See Figure 4. Obviously, in the capacitor C, the output voltage V is output during the discharge. The corresponding voltage value will not be reached, the input stage is not possible to obtain the feedback voltage Vf, and thus, the input stage will be negative in the transition pulse through the input stage. Feedback is out of control, causing the input stage to overload, the output will be severely clipped (Figure 3 A), causing transition pulse instantaneous distortion (Figure 5). If a sinusoidal signal is stacked on the transition pulse waveform, the output also obtains the intermodulation frequency ingredients of many input signal spectrum, which is TIM distortion. Tim distortion and music signals also have a close relationship, large volume, high frequency, high frequency, and high frequency, which is easy to induce TIM distortion. Serious TIM distortion reflected in the listening in similar high frequency alternating distortion, and the weak TIM distortion gave people a "metal sound" unhappy, resulting in deterioration of sound quality. So far, the sound industry has controversial for TIM distortion, but this is a deepening of people, it makes the simultaneous changes in the design idea of the amplifier, that is, more focused on the dynamic performance of the amplifier rather than just satisfied with static technical indicators Improvement. Third, the amplifier input stage - differential and total-caceri-symmetry and balance is the direction of the circuit development. Perhaps one of the perfect signs of the world. Music pays attention to balance and unity, the art is equilibrated with color, and is harmonious, in the design, often takes a seemingly disaggregated design, which is also in order to obtain a visual equilibrium. What is said above is art, symmetrical and balance gives people a stable, perfect feeling. Interestingly, there is a similar effect in the power amplifier, symmetrical and balance. Examples of symmetrical design were initially described, the complementary symmetry circuit was initiated, and the two opposite transistors were pushed out in one of the two isofficial transistors, which not only eliminates the bulky output transformer, but also in the process of pushing. The fidelity has been greatly improved. Later, people from the design of the op amplifier to enlighten, the left and right symmetrical circuits are used for the input stage of the power plants, the stability and linearity of the circuit are improved, and the circuit structure is shown in Figure 6. This structure is until today. If you review with modern vision, this circuit is a little bit. The main defect of the circuit is that the voltage promotion level, because Q1 undertakes the main task of providing voltage gain, inevitably open, and the frequency band is narrow. In this figure, the OCL amplifier is typically, the overloaded capacity of single tube amplification is also very poor, and the disadvantage of this series is not conducive to the dynamic performance of the circuit. A variety of structures have been proposed around the performance of the improved voltage push level, and the common-common base circuit is a typical example.
The common-common base circuit is also called the "Star Man" circuit. It is originally a structure in high frequency circuits to be widely used, but it can also exhibit excellent performance in the audio circuit. The first is its broadband sound, due to the very low input impedance of the coplante, so that Q, loss of voltage gain, and the impact of the Maitre Effect is very weak. The broadband push-up step is opened with the distance of the input stage, and the phase compensation becomes very easy, and the capacity C capacitance C can be greatly reduced, which is very advantageous for improving TIM distortion. The second advantage is that the high linear linear of the circuit: the output characteristics of the common base circuit can also clearly show this, and some people have been tested, and the distortion of the co-current base circuit is lower than the single tube co-transmissive circuit. It is still an imbalanced design that is derived from the input stage. If you change the input level, from complementary push-pull Q: and QG's collector output signal, the voltage push level can add a set of NPN tube composed of a group of NPN tubes on the basis of Figure 7. Push-pull output, at this time, the circuit is very symmetrical, which has almost achieved the degree of perfect. Many of the most advanced power amplifiers today also use this circuit structure. Fig. 8 is a form of another voltage push level, its input signal comes from QL and QS in Fig. Of course, the Qz must be added to the collector load resistance. The voltage push level also uses a symmetrical differential amplification, which can not only improve the balance of the input stage, improve the amplification capacity and common mode suppression ratio, but also reduce the distortion of the promotion, because the differential amplifier circuit is in a certain When there is a linear transmission characteristic, some circuits are also negative feedback retrogractive in QN, Qz emission, and more expanded linear range. Q2 and QD constitute a mirror current source, transferring Q, collector current to Qz, so although it is a single-ended output, current driving capacity is doubled than the original. Pioneer's M22K power amplifier uses this circuit structure that has achieved very good results. Symmetrical and balances are not only reflected in the structure of the circuit, but also in the parameters of components. The differential circuit is a widely used structure in integrated op amps, which is based on two differential tubes HRS and VSS precise matching. Similarly, in the push circuit, if the transistor characteristics of the two is inconsistent, the two and a half cycle of the waveform cannot be enlarged, which will increase the distortion of the increase in power. With the changes in the source, the music includes a large number of transients, high-energy ingredients. To perfectly reproduce these details, the amplifier requires a good dynamic response, and the requirements for transistor pairing are not only static HRR and VBE matching. And it is also highly matched during dynamics, which undoubtedly puts a more demanding requirements for the balance of component parameters. Fortunately, the advancement of semiconductor technology provides us with this possibility, various differential pairs, transistor arrays are inconsistent, and a single transistor consistency is also greatly improved. It is these high-quality components that make the advantages of symmetrical circuit design, and today I see a full-negative feedback circuit will not feel surprised, because there is already a good open-loop performance, why bother to be a few Data on the instrument to sacrifice the dynamic response of the amplification circuit? Fourth, the amplifier power supply and the modern amplifier "amplifier is not a power modulator", this sentence has an enlarged substance. In this case, what reasons do not cause high attention to the power supply. The power source is used as the source of the speaker, and it should never find a rectifying power supply in the past. There are two aspects of the requirements for power supplies, namely the rolling noise, and strong output capabilities. Noise is relatively easy to do, as long as the capacity of the filter capacitor can be increased, but it is not easy to do output.
First, we must increase the capacity of the power transformer, which is inconsistent with some amplifier production plants in the past, because the power transformer capacity will increase the cost, the weight and volume of the whole machine will increase; but now listen to the small speakers More and more people, these small speakers are very efficient, some famous speakers such as Cenow Si 6O0 or RO3ERS LS3 / 5A, very big food is difficult, plus modern program signals often appear some shells explosion, gongs and drums The sound, the amplifier is an extremely severe test, the same two 100W amplifiers, one possibility to make you feel the shocking power of the cannon, and the other may be like a broken drum in "咐" ring. Therefore, the power reserve of modern high-quality power amplifiers is very amazing, often using huge annular transformers, with capacitors with capacity of tens of thousands or hundreds of thousands of emblems to increase the instantaneous supply of power. Kreli's power amplifier claims that "power engine", such as KSA 250 efficiency, output power is 250W / per channel at 8 Ω, 4 Ω is 5O0W, 2,000 WΩ is 1000W, and LΩ is 2000W, and the distortion is less than any state. 0, 1%, it's amazing! Marklevi2zson's products are also an extreme attachment of power supply. Increase the quality of the power supply, not only the amount is increased, but also improves the quality. Filter capacitors are a key, in addition to the smooth filtering and energy storage effect, or the channel of the audio signal, the high quality amplifier often produces a capacitor produced specifically for sound uses to obtain a better sound quality. In the Krellkas amplifier, the power part actually powered by a regulated power supply. This machine can output 400W power in a purely state. To this end, the power part has also paid a cost of 60 high power transistors. An a by-product of the power supply is that the Amplifier is again fashionable (this is not a debit). The Amplifier has always been applied because of the power consumption, low efficiency and failure to be applied in large power amplifiers, but it natural advantages are no traffic, no change, and the harmonic components are mainly even harmonics. It is very pleasing to listen to the audience, so some extremely fever enthusiasts and manufacturers still do their best to make a matrix amplifier, and the increase in power reserves provides favorable conditions for making a A amplifier. V. Other types of amplifiers, the best power amplifier has not stopped the study of power amplifiers, and new components, new circuit forms, new theories, and amplifiers research also target these three Aspects are fully spread. On the device, the VMOS tube used is a new trend since the 1980s. VMOS tube frequency is wide, linear, no secondary breakdown, and voltage push, etc. A series of advantages have attracted more and more users, and its tone is also very close to the tube, which is a taste of the biliary fans. Nowadays, it is mainly lacking many P-channel complementary tubes, which believes soon. IGBT is also a new device that is worth noting, which is composed of MOS tube and bipolar transistor, and there is an advantage of voltage excitation and bipolar transistor pressure reduction in VMOS tube. The research of circuitry is the most active in Japan. In recent years, some companies have proposed a series of circuits from a new perspective, such as Yamaha's ALA, SONY current transmission, Technics's Class Aa, Denon's double superliner, and The UK QUAD's current pour is trying to eliminate the generation of distortion, but people more appreciate the amplifiers that do not bring these additional measures based on fine components and exquisite processes. In addition, the precision relationship between the objective technical indicators of the circuit and the subjective sound quality remains to be clarified, which requires new theory as guidance.
Domestic and foreign scholars put forward new theories from different perspectives, some believe that the dynamic auditory upper limit of the human vessel exceeded 20kHz, some proposed the concept of roll-out, and considered that human ear's distortion of different frequencies is different. Perceived the value, from 10% to 0.01%, and give the experimental value curve. Under the above viewpoint, it is inevitable to make the band wider, the full-band distortion is extremely low, and the program source has to be improved, and of course the correctness of these theories requires the inspection of practice. New technology leaps are often new materials, new theories, and the emergence of new methods, and the audio amplifier will not exceed the exception. In the era of the new day of technology, we have reason to look forward to the appearance of a more perfect power amplifier. /1.20Hz is a conservative human hear sense range, after testing, some people can hear 16 Hz sound. 2. Although the closed box is low, the sound is better than inverted. 3. The horn is referring to a treble unit. Features is that the output power is large and the efficiency is high. High sensitivity, big distortion. Commonly used in the performance site (of course, there is low distortion) 4. The reverse phase box is higher than the low frequency sound pressure obtained in the closed box of the same volume, which is also calculated by various parameters. The length, area, location of the poured inserted pipe. 5. Now domestic power amplifiers, it is also easy to do as low as 1 Hz, that is, low frequency almost extends to DC. The amplifier and the distortion of the CD machine can be very low. For the current audio system, distortion is mainly in the speaker. 6. The occasional harmonics can improve the hearing, which is why many European business boxes are increasing even harmonics. 7. Personally think that European boxes such as Denmark, the United Kingdom has more sound, the United States pay more attention to technical indicators, low distortion, and Japan's relatively kits. Domestic has also made a long progress in these years. 8. The Q value of the speaker system generally refers to the Q value of the low tone unit. The Q value suitable for inverted phase box should be 3 to 5%. The Q value of the landlord is generally better in the range of 0.5 ~ L, and such a box low frequency I am afraid. 9. Can the landlord say that the picture eight and the sixth can be posted? 10. I am a primary enthusiast, sincerely hope to communicate with the landlord. Because it is very difficult to encounter online. 11. How many speakers and amplifiers do the landlord? Can you communicate your design with me? 12. I have the opportunity to put things in the things, communicate with you, and improve
