Countercurrent 1982

Chapter 137 Technical Reserve

In fact, when Duan Yun was in school, the radio hobby group he joined had done some production and research on speakers.

At the beginning, Duan Yun only had a little understanding of the principle of sound production, but fortunately there are a few music enthusiasts in the club, and Duan Yun also learned a lot about sound quality and music from them.

Later, with the cooperation of all members of the club, Duan Yun and the others DIYed a set of speakers with good performance. Except for a small part that was given to some teachers in the school, the rest were all sold to classmates in the university. As for the end, basically every dormitory in the school uses the speaker equipment they modified.

Duan Yun vaguely remembers the principle and method of making this speaker back then.

In fact, if you want to make a high-level speaker equipment, you must understand some basic theories of acoustics.

Generally speaking, the human ear has the characteristics of being sensitive to intermediate frequencies and insensitive to low and high frequencies, which requires that the low and high frequency components be increased when reproducing music.

Secondly, the low frequency is non-directional, the intermediate frequency is more directional, and the high frequency is more directional.The positioning, direction, and surround of the sound by the human ear are mostly in the mid-to-high frequency band.

There is also the application of SRS technology.

The so-called SRS technology is a general term for a series of world-renowned audio patent technologies. The full name of SRS is Sound Retrieval System, which means sound restoration system. The essence of SRS audio technology is based on the principle and mechanism of the human ear to perceive the spatial information in the acoustic signal, to extract and restore the spatial information lost during the transmission of the acoustic signal (including compression and decoding), and to reproduce the real surround for the audience Stereo sound, like being in a live three-dimensional sound field, is called "visible" sound.

Since the positioning, direction, and surround effect of the human ear to sound are mostly in the mid-to-high frequency band, the application of SRS technology is based on the mid-to-high frequency band. SRS technology is a frequency shift and time delay technology.Why can people hear a train coming and going?Due to the Doppler effect, the frequency of sound from a moving sound source is altered as it reaches our ears.

As for the technology in circuit design, Duan Yun also conducted repeated design and research with other team members in the interest group in his previous life.

The lower the frequency, the greater the energy contained, and the higher the frequency, the less energy it contains.

It is better to use separate FET circuits for low-frequency circuits to cope with the large dynamics of low-frequency energy.

In terms of circuit design, due to the existence of a wide spectrum and the large difference in energy corresponding to low frequency, intermediate frequency, and high frequency, audio in different frequency bands should be amplified separately, and different components and circuits should be used to reduce distortion.In fact, the DTS system is superior to the Dolby system in that the low frequency below 80Hz of each channel is separated and amplified separately, which greatly reduces the burden and distortion of the mid-high frequency surround power amplifier circuit, and reduces the cost.

Finally, the choice of speakers is also very knowledgeable.

Because the low-frequency sound is easy to diffract and interfere with the sound power, the low-frequency speaker should adopt a closed design, but considering the damping of the air flow on the low-frequency speaker, the exhaust hole should be made in a zigzag shape and a flexible sound-absorbing material (that is, a sound-absorbing tube. Ideal The subwoofer speaker is: the front of the paper cone is made into a low-frequency resonance/resonance cavity, as if the speaker is placed at the bottom of the urn, and the silencer tube is connected to the back of the paper cone, and the volume of the silencer cavity is minimized to reduce resonance).

Or use a passive diaphragm to make a closed type. A simple inverted hole will lose low-frequency sound power, while medium and high frequencies are not prone to diffraction interference and reflection due to high frequency and short wavelength. Therefore, mid-high frequency speakers can be made into reflective speakers and inverted holes. type speakers to increase sound power and reduce playback distortion.

Frequency division playback is also the key to speaker production. It prevents low-frequency large current from flowing into mid- and high-frequency speakers to reduce distortion. Similarly, prevents mid- and high-frequency current from flowing into low-frequency speakers to reduce mid- and high-frequency losses.Only by split frequency playback can the effects of clear midrange, crisp treble and powerful bass be achieved.

Although Duan Yun now has a complete design idea in mind, it is difficult to make the high-quality speakers that he DIYed in college with the current conditions of his workshop and the materials and equipment he can buy.

But considering the popularity and commercial value of speaker equipment these years, it is still worth Duan Yun's technical reserves.

At present, Duan Yun still mainly produces TV antennas, but after he earns enough money by selling antennas, he can consider purchasing equipment through some special channels to expand his workshop.

Now Duan Yun Workshop can try to make one or two speaker samples, but this is far from mass production, and Duan Yun still needs a lot of equipment and technology.

In addition, Duan Yun has established a sales network with a large number of "high-quality consumers" through selling antennas and after-sales services, which has largely avoided the government's crackdown on speculation. powerful channel.

Today is Monday, after Duan Yun made some improvements to the circuit diagram of the audio system, he saw that it was almost 07:30, so he left the studio and rode a bicycle to the staff night school.

But before he rode to the Workers' Club, he heard a woman's voice behind him.

"Duan Yun!"

Duan Yun looked back when he heard the words, and found Yu Shulan was riding a phoenix car, and she quickly chased after her.

"What a coincidence." Duan Yun also greeted with a smile.

"Where did you go on Sunday?" At this time, Yu Shulan showed a trace of displeasure on her face, and continued, "Didn't we agree to meet at the entrance of the club at one o'clock in the afternoon last time to go roller skating together? I had to wait there for almost an hour..."

"Ah..." Duan Yun suddenly realized when he heard the words, and said with an apologetic expression: "I forgot about this, I'm sorry, by the way, isn't Cheng Qingyan going with you?"

When Duan Yun sent Yu Shulan home last time, Duan Yun said that if he had time, he would go to play together. Forget it.

"Both of you are big liars!" Yu Shulan pouted slightly, and said angrily, "Cheng Qingyan is still at home drawing pictures on her first Sunday, and you can't even see a shadow! In the end, I didn't go alone become!"

"Hahaha!" Duan Yun laughed when he heard the words.

"You're still laughing!" Yu Shulan glared at Duan Yun, and said, "It's a pity that I still treat you two as friends, but none of them are reliable..."

"Okay, you don't have to be angry anymore. This Sunday, I'll bring a few more friends. Let's go roller skating in the city together. I'll cover all the tickets for food and drink. This is the head office." Seeing Yu Shulan's angry face Duan Yun immediately suggested.

(End of this chapter)