The number of channels supported by a speaker is one of the important indicators to measure the quality of a speaker. From mono to the latest surround sound, the following is a detailed introduction:
Mono is a relatively primitive form of sound reproduction, and early sound cards used it more commonly. When playing back monaural information through two speakers, we can clearly feel that the sound is transmitted from the middle of the two speakers to our ears. This way of recording that lacks a sense of position is naturally very backward from the current perspective, but when the sound card just started, it was already a very advanced technology.
The mono channel lacks the positioning of the sound, and the stereo technology has completely changed this situation. The sound is allocated to two independent channels during the recording process to achieve a good sound localization effect. This kind of technology is particularly useful in music appreciation. The listener can clearly distinguish the direction from which various instruments come from, which makes the music more imaginative and closer to the on-site experience. Stereo technology is widely used in a large number of sound cards since Sound Blaster Pro and has become an audio standard with far-reaching influence. To this day, stereo is still a technical standard followed by many products.
The basic concept of a quasi-stereo sound card is: use mono when recording sound, and sometimes the playback is stereo, sometimes mono. Sound cards using this technology have also been popular on the market for a while, but they have now disappeared.
4. Four-channel surround
People's desires are endless. Although stereo has met people's requirements for the experience of the left and right channel positions, with the further development of technology, people have gradually found that dual channels can no longer meet our needs. Since the appearance of PCI sound card has brought many new technologies, the most rapid development is three-dimensional sound effects. The main purpose of the three-dimensional sound effect is to bring people a virtual sound environment, through the special HRTF technology to create a sound field that tends to be realistic, so as to obtain better game auditory effects and sound field positioning. To achieve good results, only relying on two speakers is far from enough, so stereo technology seems to be stretched in front of three-dimensional sound effects, but four-channel surround audio technology solves this problem well.
Four-channel surround stipulates 4 pronunciation points: front left, front right, rear left, and rear right, and the audience is surrounded in the middle. It is also recommended to add a subwoofer to enhance the playback processing of low-frequency signals (this is the reason why 4.1-channel speaker systems are widely popular today). As far as the overall effect is concerned, the four-channel system can bring surround sound from multiple different directions to the listener, can obtain the auditory experience of being in a variety of different environments, and give users a brand-new experience. Nowadays, four-channel technology has been widely integrated into the design of various medium and high-end speakers, becoming the mainstream trend of future development.
5.1 channels have been widely used in various traditional theaters and home theaters. Some of the more well-known sound recording compression formats, such as Dolby AC-3 (Dolby Digital), DTS, etc., are based on the 5.1 sound system. The ".1" channel is a specially designed subwoofer channel that can generate subwoofers with a frequency response range of 20 to 120 Hz. In fact, the 5.1 sound system is derived from 4.1 surround, the difference is that it adds a center unit. This center unit is responsible for transmitting the sound signal below 80Hz, which is helpful to strengthen the human voice when watching the film, and concentrate the dialogue in the middle of the entire sound field to increase the overall effect. I believe that every friend who has really experienced Dolby AC-3 sound effects will be impressed by the 5.1 channel.
Don't think that 5.1 is already the pinnacle of surround sound, and a more powerful 7.1 system has appeared. On the basis of 5.1, it adds two pronunciation points, center-left and center-right, in order to achieve a more perfect state. Due to the relatively high cost, the signal-to-noise ratio is not widely used.
The signal-to-noise ratio refers to 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, the lower the noise.
The minimum requirements of the International Electrotechnical Commission for the signal-to-noise ratio are that the preamplifier is greater than or equal to 63dB, the post-stage amplifier is greater than or equal to 86dB, and the combined amplifier is greater than or equal to 63dB. The best value of the signal-to-noise ratio of the combined amplifier should be greater than 90dB, the signal-to-noise ratio of the CD player can reach more than 90dB, and the high-end one can reach more than 110dB. When the signal-to-noise ratio is low, the noise is serious during small signal input, and the sound in the entire range is obviously muddy. Therefore, it is not recommended to buy speakers with a signal-to-noise ratio of less than 80dB, and a subwoofer with a subwoofer of 70dB is not recommended for the same reason.