Audio knowledge

Audio knowledge

For any audio equipment, no matter home or car audio, the part about signal control is extremely important. In recent years, in the high-end audio industry, especially the so-called Hi-End level system, there is a trend of gradually simplifying the preamplifier to pursue the effect of original sound reproduction.

For the home theater system that is gradually becoming the mainstream at present, signal control is very important and necessary, because in the multi-channel system planned as a movie theater space, a bunch of speakers must perform their duties and send out the corresponding sound. Only certain sounds can present the correct sound field positioning. Car audio is also a multi-channel system, so the signal processing is also the same. If you consider the uneven interior of the car and the different space factors depending on the car type, the importance of the front stage is even more undoubted.

What is the preamp? It can be simple or complex, because as long as it is part of signal processing and control, it is the pre-stage mechanism. The general power amplifier is called the rear stage, and all the processing mechanisms for the music signal between the sound source and the amplifier are called the front stage. Don't think that the preamp is very complicated. In fact, the volume control on the general audio host is part of the preamp. It controls the signal strength. In addition, the adjustment of high and low tone, left and right balance, front and rear volume adjustment, and loudness control are all part of the front stage.

There is also an audio equalizer (EQ) that is more complicated, that is, there are several frequency bands to adjust the strength of each frequency band. There is also the standard equipment of many mid-level hosts today-digital sound processor (DSP), which is a program that mixes the sound wave characteristics of space factors into digital signals to create various sound field effects, such as clubs, dance halls or Acoustic characteristics of spaces such as concert halls. In addition, equipment such as parametric equalizers used to correct frequency response changes and distortions caused by spatial factors, adjust fixed-point frequencies, and active electronic crossovers used to divide signal frequencies belong to the pre-stage.

To put it simply, any mechanism that deals with signal processing or adjustment is the pre-stage. Therefore, the importance of the front stage to the car audio can be clearly seen here, because the quality of signal control plays a key role in determining the audio from the rear stage and even the speaker.

Explanation of proper nouns

1. Loudless loudness control: Due to the limited space in the car and the noise during driving, most audio systems will have insufficient bass. If there is no subwoofer system, the bass effect is usually not good, so most manufacturers will add a loudness control to the main unit to gain the low-frequency signal. The adjustment of this part is best used when the subwoofer is not installed. If the adjustment is too strong, sometimes it will affect the purity of the sound quality.

2. Audio equalizer (EQ): In the compartment, the frequency response will be poor due to factors such as equipment selection, installation, and space. Therefore, within the 20-20KHz frequency range that can be heard by the human ear, the frequency is divided into several segments. Adjustable frequency bands for fine tuning to obtain the best frequency response. Generally speaking, the more divided frequency bands, the better. At present, the 30-band model is the mainstream model on the market, because it has the most frequency bands, and it meets the theoretical requirements of one-third intervals in acoustics (every octave is one interval, and the human ear is sensitive to The frequency response sensitivity of the sound is ten intervals, divided into one-third, so that there are no two semitones in the same adjustment frequency band, so most advanced equalizers are divided into 30 segments).

3. Digital sound processor (DSP): It is designed by digital chips and mixed with the sound wave characteristics of spatial factors, such as sound delay, reverberation, reflection and other sound affecting signal factors that cause different spatial feelings, so as to create such as concerts, clubs, etc. , nightclubs, clubs or concert halls etc. Generally speaking, DSP models with pure digital signal input are better, because the input digital signal is directly mixed with digital components for sound characteristic correction, and then converted into analog signals, which will be more natural and pure, so digital input is advanced DSP Model exclusive equipment. In addition, the general DSP will have the function of audio equalization, and some advanced models even have parameter equalization!

4. Parametric equalizer: This equipment is completely designed for the influence of frequency response caused by space factors, because in the compartment space, there will be considerable frequency fluctuations in certain frequency bands due to interior materials, space shape, size, volume, etc. distortion. The parameters are similar to the previous equalizer, but the adjustment of parameters is added to the adjusted frequency band. The so-called parameters are the width of the adjusted frequency band, which is the professional Q value. The higher the Q, the smaller the controlled frequency band, and vice versa. Because of the addition of parameter control, there is no need for too many frequency bands, just set the frequency bands that are more prone to frequency problems on the car.

5. Electronic crossover (ENC): A control mechanism that divides, distributes, and intercepts full-frequency signals. It is professionally called an active crossover network. It has three technical terms, here is also an explanation - (1) Qualcomm HI-PASS: It means that the filter only allows the signal with a higher than the frequency point to pass, and the signal with a lower than the frequency point is passed according to a certain slope Drop, suitable for tweeter; (2) Low-pass LOW-PASS: means only let the signal lower than the frequency point pass, used in bass WOOFER or subwoofer SUBWOOFER; (3) Band-pass BAND-PASS: with high and low Two crossover points, only let the frequency between them pass, and filter out the rest of the frequency, used in midrange MIDRAGNE or WOOFER. For example, when you want to separate the ultra-low frequency signal of 63Hz, you can divide the whole frequency band into 63Hz Low-pass for the subwoofer; and the frequency above 63Hz is handed over to the main sound field for processing, which is the active frequency division of the high and low channels. In the same way, if each unit is controlled by this signal frequency division method, it is called a fully active audio system.

6. Specifications: Some pre-amplifiers are also designed to be the same size as the main unit in standard DIN specifications, and even in appearance, they are also consistent with the same series of main units to match each other. Most of the front-end equipment is an independent stand-alone unit, but some front-end equipment separates the body from the control mechanism, and the control function is designed on the main unit, while the front-end equipment can be installed elsewhere, which is more convenient.

7. Signal input: refers to the way of signal input and the number of groups of input digital or stereo (left and right) sound channels. Most of the optical fibers are dedicated to digital input, and the RCA connector is a common coaxial analog input on general car audio; in addition, there are more advanced analog inputs that use BNC coaxial or XLR balanced input signals.

8. Signal output: refers to the signal output mode and group number.

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1. There are many types of pre-stage equipment, and the equipment to be installed depends on the needs.

2. The stronger the function of the front-end equipment, the more room it can provide for signal adjustment.

3. The more complex the system is, the more pre-stage equipment is required, so part of the cost of pre-stage control cannot be saved.

4. As long as all your systems are driven by power amplifiers, you must at least have an active crossover, otherwise it will damage the speaker unit, unless your power amplifier has built-in this function.

5. The higher the signal-to-noise ratio (S/N) and stereo separation of the front-end signal, the purer the sound.

6. Most of the pre-stage signals can output more than 5V. The higher the output, the less the interference of noise during long-distance transmission.