table of Contents:

The first chapter of the home theater audio debugging full analysis of the speaker wiring debugging

The second chapter of the home theater audio debugging full analysis of the subwoofer settings

Chapter III Use of Sound Analyzer for Full Analysis of Home Theater Audio Commissioning

The fourth chapter of the home theater audio debugging full analysis of the power amplifier configuration

The fifth chapter of the home theater audio debugging full analysis of the impact of the power supply

The sixth chapter of the home theater audio debugging full analysis of the two-line crossover

The seventh chapter of the home theater audio debugging full analysis of the top ten lies in the audio industry

The fourth chapter of the home theater audio debugging full analysis of the power amplifier configuration

First fill the foundation, then talk about the speaker system and amplifier configuration.

About the relationship between speaker power and room area!

I used to see the speaker power and room area on the Internet, which can be roughly controlled at 5W/m2.

Then a 12 square meter room is generally 60W enough. This 60W means that each speaker in 5.1 is 60W or 5 speakers in 5.1 and 60W (except subwoofer)? Do you have a rough ratio between room area and power? What percentage of the box-mounted surround gun should roughly fit the room area?

If that theory is true, of course it means every channel. Home theater, a reasonable requirement is that the sound pressure reaches a certain value, which many of us can't reach. The sound pressure is related to the power input to the speaker, that is, the output power of the amplifier and the sensitivity of the speaker, so it is impossible to split the pursuit of power. However, home theater systems, especially transistor power amplifiers, power headroom is necessary. Therefore, under household conditions, we generally do not consider the minimum power, and can invest more.

Amplifier: A general term for preamplifiers and power amplifiers.

Power Amplifier: A type of electronic device that is used to enhance the power of a signal to drive the sound of a speaker. A power amplifier without an accessory function such as source selection and volume control is called a post stage.

Preamplifier: The preamplifier and control section before the amplifier, used to enhance the voltage amplitude of the signal, providing input signal selection, tone adjustment and volume control. The preamplifier is also called the preamplifier. Used for jukeboxes and playback equipment

Post-amplifier: The machine used to connect the speakers, which matches the impedance of the speaker and matches the power.

(The signal source is connected to the amplifier. The front stage is connected to the rear stage. As long as the input impedance of the latter stage is greater than 5-10 times of the output impedance of the previous stage, the impedance matching is considered good. For the amplifier connected speakers, the tube machine should be selected. Speakers with equal or close to the nominal impedance of the output, and transistor amplifiers without this limitation, can be connected to any impedance speaker.)

(The voltage of the sound signal released from the CD is too small to be directly amplified by the power amplifier stage of the power amplifier. Therefore, it is necessary to have a voltage amplification stage to amplify the sound signal to a certain extent before the power stage can be connected to the speaker to release the sound. The voltage amplification stage is the so-called pre-amplification, and the power amplification stage is called the post-stage amplification. The high-level sound is separated by the front and rear stages, which are two things. When used, the two things are used together. What is combined into a circuit board is a thing, called a combined power amplifier... I don’t know if I said it clearly? The combined power amplifier usually has a front and rear stage, and also has a pure final stage power amplifier, which is only responsible for amplifying the signal current, that is, increasing The driving ability of the signal is to drive the speaker. The independent of the front stage is generally not called the power amplifier. Devices such as the mixer can be called preamplifiers. The preamplifier is responsible for the amplification of the signal, so that the signal can be processed by the post amplifier. Amplitude.)

Consolidated Amplifier: An amplifier that combines preamplification and power amplification in one chassis.

Amplifier: Another way of saying that a tube amplifier.

Carousel: It is an important device used to reproduce the sound waves of vinyl records. The most common ones are moving magnetic pickups and moving coil cartridges.

Coaxial horn: The coaxial horn is a tweeter placed at the center of a mid-bass or woofer. These two monomers are not full-range, but each has a crossover network. The advantage of this is that there is no time phase problem in the position of the single placement. The sound waves of the two monomers reach the listener's ear at the same time, and the audio and video are accurate and loose.

Horn Horn: It is a vocal compression drive with a horn throat, and finally a horn opening to form a complete horn loudspeaker.

Rated power: For power amplifiers, the rated power generally refers to the RMS power that can be continuously output. For the speaker, the rated power refers to the power that the speaker can withstand this value for a long time without damage, which does not mean certain The power amplifier that needs such a high power is pushed, and the difficulty of driving the speaker is mainly determined by its sensitivity and impedance characteristics. It does not mean that it cannot be equipped with a power amplifier whose output power is greater than the rated power of the speaker. Just like driving a car, driving a sports car with a speed of 300 kilometers is not the same as a car accident. You can't drive it so fast. Similarly, as long as the volume is not blindly increased, high-power amplifiers can be equipped with low-power speakers.

Peak Music Output Power (PMPO): The output power calculated from the peak voltage that can be reached instantaneously by a music signal, whose commercial significance is greater than the actual effect. PMPO power can be three to four times higher than the internationally recognized rms rated output power (RMS). For example, the early portable recorder had an RMS power of only 4 or 5 watts per channel, but with PMPO, the value can be increased. Up to 20W or so.

Single-ended amplification: The output stage of the amplifier is amplified by two a half cycles of positive and negative signals by an amplifying component (or multiple components but in parallel). Single-ended amplification machines can only take Class A work status.

Push-pull amplification: The output stage of the amplifier has two “arms” (two sets of amplification components). When the current of one “arm” increases, the current of the other “arm” decreases, and the states of the two are alternately converted. For the load, it seems that an "arm" is pushing, and an "arm" is pulling to jointly complete the current output task. Although Class A amplifiers can be push-pull amplifiers, it is more common to use a push-pull amplifier to form a Class B or Class A amplifier.

Class A: Also known as Class A, a class of amplifiers that do not have a current cutoff (ie, stop output) for any power output component of the amplifier over the entire period of the signal (positive and negative sine waves for two and a half weeks). Class A amplifiers generate high heat during operation and are inefficient, but the inherent advantage is that there is no crossover distortion. Single-ended amplifiers are Class A working methods, and push-pull amplifiers can be Class A or Class B or Class A.

Class B: Also known as Class B, the positive and negative sinusoidal signals are amplified by the two "arms" of the push-pull output stage. The conduction time of each "arm" is the half cycle of the signal. . Class B amplifiers have the advantage of high efficiency and the disadvantage of crossover distortion.

Class A and B: Also known as class AB, between Class A and Class B, each "arm" conduction time of push-pull amplification is greater than half a cycle of the signal and less than one cycle. Class A and Class B amplification effectively solve the crossover distortion problem of Class B amplifiers, and the efficiency is higher than that of Class A amplifiers, so it has been widely used.

Talk about the speaker system and the configuration of the power amplifier. The speaker system should reproduce various music programs with high quality. According to the properties of the music signal, the peak factor is about 10-15dB. From the perspective of ensuring the sound quality, the power amplifier should be within this dynamic range. There is no limiting situation, that is, the maximum output power of the power amplifier should be 5-8 times of the rated power of the speaker. Although the power quality of this power configuration is very good, its investment will be very large, so this power ratio will generally be determined. The rated power of the speaker unit at 1-2 times. 1-2 times this range may be space-wide, we can give you a more specific experience.

1. In some low-cost and investment limited engineering amplifiers, the power is at least equivalent to the rated power of the speaker, but pay great attention to keep the sound undistorted. The too small power configuration does not seem to damage the speaker unit, but it is not too small. It is extremely prone to overload clipping, generating a lot of harmonics and burning the tweeter.

2. General engineering recommends that the power of the amplifier be 1.5 times, and the bass part should be more than 1.5 times, so that you can get enough power. 3. Highly demanding sound, such as studio monitoring, concert halls, etc., ideally double the power of the speaker (this is consistent with one of the recommendations of the International Electrotechnical Commission's IEC standard for mating standards) There is no hard standard for power amplifier power, depending on the investment budget and the sound quality requirements.

How do you match the power of the speakers and amplifiers? I believe that everyone will generally say several options. Some people say that the power of the amplifier should be 1.2-1.5 times larger than that of the speakers. Some people say that the power of the amplifier is twice as large as that of the speakers. Some people say that 1:1 is also Row. What is the doorway in the end?

First, the speaker, according to the AES standard, the general speaker can withstand the instantaneous peak input power 4 times (6 dB) higher than its rated input power in a short time, that is, if a nominal 300W speaker can withstand for a short time 1200W input power.

In addition, the power amplifier, according to the standards of the US FTC laboratory, in the case of sufficient power supply capacity, the power amplifier can instantaneously output a peak output power higher than its rated output power of 3 decibels, that is, a rated output power of 300 watts. The power amplifier can provide twice the peak output power of the rated output power in a short time, that is, provide 600W of output power in a short time. Then, if you want a power amplifier that can provide 1200W peak output power, the power amplifier's rated output power needs to reach 600W.

Well, now everyone can know through the above instructions, in order to let the amplifier and speakers fully express the performance of various music peak signals, then the rated output power of the amplifier is equal to twice the input power of the speaker.

However, in this configuration, you are not required to fully add the power rating of the amplifier to the speaker. If it is fully added, the speaker actually receives more than 1 times the input power of its rated input power, that is, the speaker is always in the super Load working state, this is a very dangerous state for the speaker.

Therefore, according to the power amplifier output power and speaker input power ratio of 2:1, the purpose is only to allow the speaker to express its peak output capability. However, the control of the input level of the power amplifier is stricter at this time. Under normal circumstances, for example, the rated input level of the power amplifier is 0 dB, then the power amplifier input level setting is 3 dB lower than the rated power input level, that is, the 600W power amplifier is only operated at 300W. When a signal with a peak characteristic of 4 times (6 dB) enters the power amplifier, the actual input level of the power amplifier reaches 6+(-3)=+3 dB, and the instantaneous output power of the power amplifier reaches The rated output power is 1 times, which matches the peak input power of the speaker. If you do not control the level, what kind of situation will happen? For example, the same rated 600W amplifier pushes 300W speaker, the power amplifier still according to its rated input level, then the power amplifier normally inputs 600W power, the speaker is equal to eat 1 times When the power comes in, when a peak signal of +6 dB (4 times) enters, the peak output power of the power amplifier is 2400W. However, the peak output capability of the power amplifier is only 2 times, and it cannot emit 4 times of undistorted power. What happens when you don't come out? Clipping, what about clipping? The original sinusoidal audio signal becomes a square wave. Well, the horn is easily hanged because of this square wave.

Therefore, using a power amplifier with 2 times the input power of the speaker to push the speaker has a theoretical basis, but the requirements for the system level setting are very high. If it is aimed at a master who can correctly control the level, this method can be used very well. Perfect music performance. However, if the operator is not very familiar with this, it is very dangerous.

How to set this level? There are two ways. The first one sets the normal working level of the system to 0 dB. When the output level of the device in the preamplifier stage is 0 dB, the volume potentiometer of the amplifier is reduced. Small 3 decibels. Second, set the system's normal operating level to 0 dB, and then reduce the mixer's output level by 3 dB under normal conditions. I personally prefer the former method, so the signal-to-noise ratio of the front end of the system can be increased by 3 decibels.

Having said that, a friend said: How do I control this level? This requires a limiter to help you control. If the previous method is used, if the input sensitivity of the amplifier is 0.775v (0dB), then The frame is set to +6 decibels. If you follow the latter method, the limiter is set to +3 decibels. In this way, the front signal is increased, and the peak signal level applied to the power amplifier will not exceed 6 decibels, and the system is safe.

Let's say that the speaker and amplifier power match is 1:1.

The power of the amplifier and the speaker is matched by 1:1. The speaker with 300W also has a peak receiving capacity of 1200W, while the 300W amplifier has a peak output capacity of 600W. According to the above description, that is, the amplifier enters the peak state. Under the speaker, the speaker can only get half of its peak input power from the amplifier. What's the problem with this? Friends can see that the speaker is only a little discount on the peak performance. So what are the benefits of this? The advantage is that the speaker will not be overloaded when the working level is normal. But some friends will also ask, how can I control the input signal is not overloaded? And the project is handed over, it is not my operation. To avoid this, it is also necessary to use the limiter. In other words, an input sensitivity of 0.775v (0dB), output 300W power amplifier, as long as you set the front limiter limiter level to 0 decibels, do not let more than 0 decibel continuous audio signal into the amplifier, then The output of the amplifier will not exceed 300W, so it will not overload the speaker.

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