Several audiovisual systems need to be distinguished
Before talking about architectural acoustics, we scored four basic audiovisual systems to determine what system is right for our space. According to the room type, the home space can be divided into apartments, lofts, townhouses and single-family villas. The diversity of its space has also increased, and the most functional is the single-family villa, we will use it to explain.
The first is a multi-space music system, which includes an indoor music system and an outdoor music system. The multi-space music system is different from the traditional sound reinforcement system, which allows the owner to experience the reproduction of independent music and images in each room and outside. The wall panel or the central control system can be used for song selection, channel selection, volume control, switch and other operations, so that the owner can see and hear the desired audio and video information anytime and anywhere. The requirements are very low.
Second, the stereo music system can be arranged in a hall, a study room or a dedicated HiFi room. Such a system, if the owner has high requirements on the sound quality, it is best to choose a separate room to do, the space ratio of the room, the internal structure The design has extremely high requirements, and in future articles I will elaborate on how to build a Hi-Fi room.
Third, the multi-channel reproduction system can be further divided into applications in special environments such as living rooms, study rooms, bedrooms, swimming pools, and applications in dedicated rooms.
Fourth, the performing arts system or the karaoke system can be divided into applications that share space, such as applications in space and dedicated spaces such as Hi-Fi rooms or theater rooms or halls.
The above four audio-visual systems basically summarize the application methods of all audio-visual systems in our home environment. Each application has its application characteristics, advantages and disadvantages of different structures, pre-design considerations, and product selection. Everything is stressful. In general, for Hi-Fi systems (ie, high fidelity music reproduction systems), theater systems, and karaoke systems, it is preferable to have separate spaces if conditions permit. From the perspective of professional sound construction, there are contradictions in the requirements of the acoustic environment required for these three systems. When one system is satisfied, it will damage the requirements of another system. Therefore, in the actual design, three systems are involved. To be perfect in the same space, I personally think it is impossible. As for the two applications in the same space, the sound designer needs to have a wealth of practical experience and a profound theoretical foundation. I can only talk to you about some considerations in future articles.
home theater
In this issue, we mainly talk about the widely used home theater system, that is, the multi-channel reproduction system.
The electronic sound reinforcement equipment has been in existence for more than 100 years, and it has been used until now, based on the two-ear theory stereo, which is a 2-channel sound reinforcement system. The so-called two-ear theory refers to the distribution of the human ear on both sides of the head. Since the sound waves emitted by the sound source reach a certain time difference, the intensity difference and the phase difference, the human brain can calculate the direction of the sound source and Far and near, the positioning of the sound image. The sound image localization ability obtained by binaural hearing, when the frequency is higher than 1400 Hz, mainly depends on the intensity difference of the binaural sound. Below 1400 Hz, it mainly depends on the time difference of the sound arrival, usually the human ear resolution level. The ability to align the position of the sound source is a change in orientation from 1° to 3°.
The stereo recording method and stereo playback device developed based on this theory are the Hi-Fi audio systems that we usually use. Most of the current fidelity audio systems still use such systems. The other is a multi-channel sound reinforcement system. The earliest multi-channel system appeared in commercial theaters in the United States in 1950, which is a 4-channel system. The 4.1-channel commercial cinema system was first invented by Dolby in 1975. In 1995, the 5.1 multi-channel system entered the home with the DVD, so today's home theater system evolved over the past 15 years.
To build a home private theater, both technologies must have the development of video projection technology and the development of audio multi-channel technology. Today we are talking about audio. To do the audio of the home theater, we must start from two aspects: First, the electronic audio equipment, including: power amplifier, decoder, audio processor, signal source, speaker and so on. The second is the creation of an acoustic environment for indoor buildings.
Electronic audio equipment should be selected
Playback device
For more than a decade, home theater has grown very rapidly, with video carriers ranging from DVD to BD, from 5.1 to 6.1 to 7.1. From MPEG1 to MPEG2 encoding, the data traffic is 640kbps from Dolby Digtal, 1.5mbps from DTS to LPCM 6mbps, DTS-HD master 3mbps and Dolby trueHD3mbps. The data traffic of audio is nearly ten times larger. The total amount of data in a movie ranges from 4-6G to 50G in BD. The rapid development of the original signal source provides a very high-quality program source for home theater.
Such a good source of signals provides the basic foundation for building a perfect home audiovisual system. The playback of these software is usually implemented by BD CD player, HD hard disk player and PS3 game console. Among them, the Blu-ray machine has a partition, the world is divided into three areas A/B/C, China is the C area, and the A area is backward compatible. Everyone should pay special attention when purchasing. The high-definition program hard disk player has copyright problems, the products of various brands are mixed, and the stability of some products is very poor. From the source of the program, there are many sources that cannot achieve high definition. The PS3 game console has a fast reading speed, adjustable area, and ideal audio and video effects. The cinema system is the best choice for the overall system cost of 300,000.
Decoder and amplifier
To understand the source of the signal, let's talk about the decoder, audio processor, amplifier. In systems with less than 400,000, these devices may be integrated into one or two devices, such as the amplifier itself incorporating a decoder and an audio processor. The bass power amplifier needs to have functions such as crossover point adjustment, Q value adjustment, phase adjustment, and delay adjustment. The good bass is an independent power amplifier, and there are very fine adjustments of various parameters on the power amplifier to adapt to the arrangement and combination of multiple basses in different positions. The main power amplifier with integrated function should have the following conditions: more than 2 sets of HDMI input, full support for 1080P16:9D video and full support for LPCM DTS-HD Dolby trueHD encoding. The rear stage power amplifier is not less than 7 channels. The power amplifier itself has a speaker impedance distance, a frequency division adjustment function, and a 7-channel independent simple equalizer to facilitate preliminary adjustment of the speaker.
Speaker
Let's talk about the speakers used in home theaters. There are four categories in terms of types: traditional speakers (in room), in-wall speakers (in wall), wall-mounted speakers (on wall), and ceiling-mounted speakers. Speaker (in celling). The four types of speakers have different settings for their audio characteristics according to different application methods and application environments. Therefore, the original product design intent must be respected in use and must not be used indiscriminately. In particular, we should pay attention to traditional speakers, because they can move freely in the room, often placed in the corners incorrectly, or placed against the wall. This is absolutely impossible. When such speakers are close to the corners, the spectrum The response curve will change dramatically and will deviate significantly from the original design curve, allowing us to hear severely distorted sounds.
Indoor building acoustic environment is very important
Positioning
First, let's talk about the precautions to be followed when building a multi-channel with a traditional speaker. Traditional speakers are designed with stereo sound reinforcement as the main purpose. The basic structure can be divided into the following categories: box structure, which can be divided into closed type, leading phase type, and rear phase type. The lower phase, the semi-maze, the labyrinth; the high-pitched speakers can be divided into electrostatic, enamel, aluminum, horn, rare material coating, coaxial and so on. Each speaker has different usages due to its cabinet structure and the combination and combination of speaker units. We will use different usages in the following articles.
Now suppose we have a room with a better ratio, height: width: 1:1.45:2.1; 1:1.28:1.54; 1:1.25:1.6; these ratios are based on us, Port, Whiteknife, Newman The results of the study suggest that the proportion of space that can be recommended, when all the floor-standing traditional speakers are used to build a home theater, basically tends to be ideally placed as shown on the right. Such a 7.4-channel system should be nearly perfect in terms of acoustic compatibility with the requirements of music appreciation and movies, concerts, etc., but it also has several features: 1) 7 speakers should be homogeneous , the same type, no channel is the concept of the main channel; 2) the best listening area is very small, can only accommodate 1 person in the picture; 3) the screen can not be very large, because the front speaker occupies too More space. But if the readers are big enough, high enough, and well-funded, this is a perfect choice. (The placement here needs to be repositioned according to the actual product. This figure is for reference only. It is recommended that the total system cost is more than 1 million.)
Acoustic requirements
It is necessary to consider the architectural acoustic requirements of such systems in order to make the basic placement. In general, we have a very important and often mentioned room parameter in the acoustic characteristics of indoor buildings, that is, the reverberation time of this room, strictly speaking, what is the coefficient of RT60.
In the 1980s, the theoretical community made great progress in the study of small rooms with a length of less than 15m on one side. It is clear that a misunderstanding, that is, the RT60 index cannot be measured for small rooms, that is, there is no existence, and it can accurately describe small The room parameter of the room shall be the initial delay interval (ISD), defined as the time interval between the first arrival of the direct sound and the first apparent reflected sound. The so-called "obvious" here refers to the initial reflection sound of the reverberant sound field peak whose sound level is close to the exponential number increase and attenuation. Too much explanation and definition and measurement methods are not mentioned here. I only hope that everyone can identify an important one. The concept, and will not be fooled by fake experts in the society on the Internet.
In the above we give the ideal spatial ratio. In this space, we have the correct speaker position, so what work should we do on the sound? The four basic steps are: 1. Absorbing sound; 2. Separating sound; 3. Spreading sound; 4. Reflecting sound. As shown below.
In the continuous application, there are hundreds of acoustic material structures. The sound-absorbing panels, cotton, and spreading materials have their own unique acoustic parameters (see attached table). This table is only four kinds of materials. The acoustic parameters are for illustrative purposes only, and other parameters are too complex. If the reader needs it, I can send it again.
The acoustic processing diagram attached to me is only used for traditional speakers to realize the division of the wall and ceiling and floor sound function areas of the 7.4 multi-channel music and cinema compatible system. In practice, according to the equipment and the inter-room environment. There are many factors that influence the factors such as furniture. I can't talk about the different design applications of the actual spreader, sound absorbing material, reflector and attractor. The A side is the screen surface, the whole wall is to be sound absorbing, the four corners are made of resonant sound absorbing body, and the ground is made of thick wool rug. The purpose of this design is to control the ISD of this room to 5ms-10ms. Between the better, the realization of the pure beauty of music and the dynamics of the cinema.
In the video section, I prefer to use the opaque 2.35:1 frame screen for this type of screen. Using this type of screen can leave room for our huge center speaker, if it is equipped with electric slides. The wide screen is moving, and when the 16:9 signal source is played, the wide screen can be automatically removed, which is basically a perfect solution. In future articles, I will elaborate on cinema optical issues.
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