This introduces the considerations and requirements for the design of the listening room during the new private house in Japan. The Yamamoto Wufu is an expert in the development of the monitor system of the NHK Institute in Japan, and is also an advocate of the 96KHz supersampling recording system. It enjoys high prestige. The following is a description of his design of the listening room in the first person.
When I was developing the monitor 2S-305 at the NHK Institute in my early years, I lived in an ordinary apartment and could not have a dedicated listening room. Therefore, I did not purchase audio equipment, and I also had a set of audio equipment. At that time, I was listening to the most advanced equipment at the Institute. When I got home, I didn’t have any mood to listen to music again.
Thirty years ago, I bought a house near the NHK Institute of Technology, but I didn’t have a special listening room. Instead, I set up a sound system in the living room facing about 10 yards in the yard, but there was soundproofing. The problem is that the door to the yard is a 5mm heavy-duty glass door, the sound will not affect the neighbors, but the living room is upstairs is the daughter's boudoir, listening to the concert late at night prevents her from rest.
For the above reasons, when the house was remodeled, consider setting up a room that would not prevent others from resting even if listening to music at 110 dB sound pressure in the middle of the night. Due to the narrow land in Japan, I bought the land near the north side of the house 20 years ago, and I am going to live with my daughter. If it is my husband and wife, I will consider another residential building as a listening room, because it is two generations. Don, so I had to decide to build the listening room in the basement.
I think that the sound quality of a sound system is firstly the sound source, followed by the sound box and the listening environment. The sound source part is aimed at 96KHz/24-bit recording software of the recently released DVD sound, and builds a listening sound with unreserved release of its high quality. room.
From the engineering sequence, the size and location of the basement cannot be started without consideration. As a two-generation house, it is also necessary to consider the room of the grandson and the dining room when the relatives visit. It is most appropriate to build a basement under it.
The shape of the 12-story room is better for the dispersion resonance frequency, but because the basement is damp, it is necessary to construct a hollow retaining wall made of light concrete slabs on the inside of the structural wall surface, and to construct a waterproof layer. If a decorative layer of 10 cm is added, The room was too narrow, so when building the basement, it was 30 cm wide on both sides.
In addition, the projector should be hoisted on the ceiling, so ensure that the ceiling to floor height is not less than 2.6 meters.
Room shape design:
To suppress the reverberation time for too long, there is a method of tilting the wall and tilting the ceiling. In this case, there are two methods of narrowing the sound source side and widening the sound source side, generally when the sound source side is narrow, the listening side is wide. However, the mirror image of the wall reflection source will be concentrated on the sound source side, so that the reproduced sound lacks the sense of width. Conversely, when the sound source side is widened, the mirror image of the sound source falls on the listening side through the wall, and the production quality and sound quality will be better. .
I personally think that the reproduction of the sound field is the task of a multi-channel system, and the stereo should reproduce the sound field in front of it. Therefore, the flat design and the east side unfolding view of the listening room are as shown in the figure, the left and right walls are inclined by 3 degrees, and the ceiling is also inclined.
Behind the front of the listening room, set up a warehouse for AV equipment and software. The speakers use the Pioneer 2404 (two-way horn + 12-inch bass).
This speaker is wider, with a retractable projection screen on the back. When using AV, the speaker switches to the Pioneer S-LH5.
As a listening room for listening to music, there should be better reverberation time characteristics. For example, the bass reverberation seems to be more appropriate. However, my job is to compare the sound quality of the equipment. I should try my best to avoid bass resonance in the small room, so use a large area. A bass sound absorbing device made of perforated plates.
The reverberation time is as follows:
The result of the listening is that the bass reverberation is less.
Regarding the design of the sound absorbing material, there are two ways of changing the sound absorbing ratio on the sound source side and the listening side, or randomly setting the sound absorbing material. There is a warehouse door on the front of the listening room, which can't absorb sound at all. At the same time, I want to form a sound field between the two speakers. To maintain the reverberation characteristics, the sound source side should be reflected. It should be said that this design is relatively good. .
The sound absorbing material on the side wall is randomly set. The sound absorbing surface is arranged on the first reflecting surface to suppress the formation of the mirror image on the first reflecting surface, so that the sound field is correctly formed between the two speakers, and the sound absorption in the second half of the side wall is made. The setting of the material is asymmetrical. On the other hand, the ceiling has an acoustic reflection, and the floor is also able to correctly reproduce the quality of the 95KHz super-sampled sound source, forming a relatively close sound field, which is the sounding of the listener with a sense of proximity. At the same time, the height of the audio and video is given up, which is the effect of the reflected sound.
Another problem in designing the listening room is the problem of ventilation. A person can listen for 2-3 hours without any problem. If you change a few people, the air will be turbid after 20-30 minutes, so you must set low noise. The ventilator is provided with an air inlet at the entrance of the listening room, a 40×50×60 cm silencer slot under the stairs, connected by an air suction pipe, and a blind window. On the other hand, the north warehouse is set up with a window, above the warehouse. A sound absorbing material is also arranged in the electrical box, and a ventilating fan is arranged on the north wall, so that the noise outside is not transmitted into the listening room, and the sound pressure of 110 dB inside is not heard at the air inlet and the air outlet.
The speaker position is first to create a speaker stand, so that the height of the Pioneer 2404 is high with the ear, the size of the base is the same as the size of the speaker, and the universal wheel is conveniently moved under the speaker frame, so that when using the projector, it is convenient to switch to the pioneer S- LH5 speaker.
Because the room is narrow, if the two speakers have enough space, the speaker has to be placed against the wall, so after changing the distance to the reflective wall, it is the best position to listen to repeatedly. To expand the listening range, the speakers are closer to the wall than they are now, but in this way, the sound field feel becomes weaker.
As a result, the current position just uses the space of the reflective surface and the side wall of the speaker to form the supposed sound field. The live performance is very strong. In addition, the sound absorbing material is placed on the reflective wall. The result is poor sound quality, lack of power and loss. Sound field feeling.
I look forward to the future. I was dissatisfied with the CD quality before the number of people. I am not in favor of returning to the historical trend of the LP era. Therefore, we advocate the 96KHz oversampling system to improve the sound quality of existing digital audio. It is a DAT with 96KHz oversampling. At present, I use the software recorded by 96KHz super-sampling by various record companies, which is convinced by its high sound quality. Recently, the DVD can realize 96KHz oversampling and 24-bit high-quality recording. , one step ahead of DAT.
In my listening room, playing 96KHz/16-bit recording software, the realism of the stage reproduction between the two speakers makes people fall into the illusion of being on the stage, the ratio of audio and video of various instruments, the accuracy of the division, and the orientation. And the sense of depth is outstanding.
Such excellent performance can be achieved through DVD. Unfortunately, in order to protect the existing record market, major record companies are not active in the development of DVD software, but current consumers do not understand the high sound quality of DVDs. Once the masses understand the sound quality, their demand will be explosive, and I am waiting for this day.
Here is also: looking tired! ! !
The indoor acoustic environment has a certain influence on the indoor sound field created by the multi-channel speaker. Different room sounds have different spatial acoustic characteristics. The multi-channel sound system uses multiple speakers to represent the sound image and create a surround sound effect. This is not an easy task. If there is no ideal indoor acoustic environment to match, then the comprehensive sound effect will not be good. According to the theory of acoustic psychology, the early reflection sound of less than 1ms in the interior is delayed. Significant interference with direct sound will make the sound become more turbid, which will affect the sound image localization. The early reflection sound between 1~30ms will have less interference to the direct sound, and it will be combined with the direct sound. It helps to increase the loudness, but it may change the tone of the direct sound. As for the reflected sound after 30ms, the human ear usually thinks it is a reverberation sound. For the above reasons, we must do a good job of sound absorption and diffusion in the audio-visual room. Acoustic processing such as sound insulation, otherwise, excessive reverberation will reduce the clarity and consistency of the sound and affect the playback sound. In order to illuminate the grand stereo field of the theater, the room for audio-visual use should not be too small. If possible, sound-absorbing materials should be added.
Second, the speaker is placed on the premise of a good indoor acoustic environment, the more accurate the sound image is positioned, the more realistic the sound is, the more it can show the vivid effect of the sound and image. First look at the placement of the speakers in the theater. The left and right channel front speakers are separated from each other by the same width as the movie screen. The front speakers are usually discharged behind the movie screen, and they can transmit the sound to the viewer through the small gap of the screen. Therefore, this speaker can be placed at half the height of the screen. The subwoofer is not necessarily placed in a symmetrical position in the front speaker cluster; the standard theater has a lot of surround speakers that, together with the front speakers, really "surround" the audience. After referring to the above examples of speaker placement, let's go back and see how the speakers should be placed for the best sound. Here, we have to pay attention to the problem that the indoor play space we encounter may be much smaller than the real theater.
Below, we will discuss the placement of three front (left, center, and right) speakers, then surround the sound box, and finally study the placement of the subwoofer.
1. The center speaker of the center channel speaker is placed as close as possible to the center of the image screen. The center channel speaker has the greatest influence on the sound quality of the movie dialogue, in order to ensure that the dialogue is accurately positioned in the center of the screen and the sound Clear, you should use a separate speaker designed specifically for the center channel, instead of the ordinary bookshelf speakers or the speakers inside the TV. The center channel speakers mostly use horizontal horizontal cabinets, the best placement It is the top of the TV (if the front projection display screen is placed behind the screen), it should be as close as possible to the screen. If the space is limited, a more economical placement scheme can be adopted, that is, no center speaker is provided. At this time, the working mode of the AV amplifier should be placed in the "phantom" center channel mode, so that the information of the center channel is balancedly released from the left and right speakers, and the sound image is just in the center of the screen, which is for the small listening room. This is applicable. Of course, it is best to set up a center speaker.
2. The placement of the left and right channel main speakers has a certain relationship with the position of the center channel speakers. In order to ensure the smoothness of the left and right movement of the sound image, they should be placed on both sides of the center channel speaker, and the three speakers should be at the same distance from the position of the best listener in front of the screen. In general, the center speaker should be placed a little longer than the left and right speakers until the sound field can be completely combined to create a truly unified sound image. The distance of the back is related to the size of the space, the listening position and the speakers used, which can be determined by experiment. In addition, the vertical height of the left and right channel speakers is preferably not higher or lower than the center speaker's axis by 0.3m (preferably slightly lower), otherwise the left, middle and right three The height difference of the speakers is too large, and the front sound image gives a sound jump when it is laterally displaced. Generally, floor-standing speakers can meet the above requirements. If you use a bookshelf speaker for the left and right speakers, you should fix them on the speaker stand so that it meets the above requirements. The distance between the left and right channel speakers leaving the screen depends on the size of the screen. If you use a large, medium-sized screen color TV in a small room, the left and right channel speakers can be placed close to the sides of the screen. If the screen is small, you can make them a little further away from the screen to get a wider stereo field. But don't go too far from the screen, so as not to give people a false feeling because the sound image position is too far from the picture. From this point of view, there is a shortage of "innate" - the environment is too small. In summary, the sound directivity of the left, middle and right three-channel speakers is heavier than the diffusivity, that is, the radiation angle range of the three channels should be oriented toward the optimal listening position. This reduces the effects of reflected sound from the floor, walls and roof, and properly ensures the clarity of the sound image.
3. Surround speaker The surround speaker is used to create an atmosphere, which also plays an important role in the entire speaker system.
A. Types of Surround Speakers Currently, there are two types of surround speakers, one is a common unipolar small speaker, which is usually placed on the speaker stand or hung on the wall. Another type of surround speaker is THX recommended dipole speakers, each with two back-to-back speakers installed, all connected in reverse phase. This kind of speaker only emits high-frequency sound to the front and rear and can not produce low-frequency sound (even Entering the low frequency signal and also not paying the bass due to the offset.) Why is this? Let's look at the working process of the dipole speaker. Two speakers are placed back to back in the speaker, and the two speakers are fed. In the opposite phase of the signal, the A speaker inputs a positive polarity signal, and the paper cassette moves forward, compressing the front air (increased density). At the same time, the B speaker inputs a negative polarity signal, and the low box moves backward, so that The air in front of it is sparse (reduced density), so the direction of the sound wave in front of the two speakers is opposite. If the two speakers feed in the full-band signal, the low-frequency is strong because of its long wavelength, so the low-frequency sound from the A speaker will Winding around The B-speaker is weakened (cancelled); while the medium-high frequency signal has a short diffractive power due to its short wavelength, the mid-high frequency sound on both sides of the speaker is small, so the offset effect in front of the speaker is not obvious, so two The speaker only emits low-frequency sounds in the front and rear, and the low-frequency sound is used. The purpose of using the dipole speaker is to avoid excessive directionality. For the audio industry, the dipole speaker is very strange. Type, this kind of speaker needs a certain development to mature and stereotype. This kind of speaker is not full frequency band, because the frequency below 100MHz has been cut off. The reason why this speaker is used is because it only sounds forward and backward at the same time. Never give a sound to the side of the listener, and let the sound reach the listener before filling the listening room, so that you can create a surround sound that suits people's hearing habits.
B. The arrangement of the surround speakers of the surround speakers should be different depending on the listening environment (room conditions) and the type of loop speakers. The speakers of the left and right surround channels should be more diffuse than the sound. Directionality, which is conducive to create a rich surrounding atmosphere. When placing dipole-type speakers, two factors should be considered: resonance and self-fading. The best anti-resonance is 20% indoor space from the ceiling (or ground). At the height (if the indoor height is 2.5m, the best position is 50cm above and below). In order to make the frequency response smoother, a new device called low-frequency "trap" can be added (absorbing low audio) to eliminate the reflection that causes the sound to self-degrad. For direct-radiation loop speakers, there are many layout options to consider. For example: fixed On the sides of the wall, and point them to the rear corner; fix them on the rear wall so that they open outwards and upwards in an inverted figure-eight shape and face the side wall to the ceiling; placed on the floor against the wall on both sides, And pointing up to the junction of the wall and the ceiling, etc. There are many other options that can be designed according to the specific conditions of the room. The surround sound field of the home theater is mainly formed by the acoustic reflection and refraction of the surround speakers in the interior, and The room acoustic conditions of different rooms vary widely. As long as the patience test and careful comparison, you will find the best placement plan. 4. The subwoofer is usually placed near the front corner of the subwoofer, preferably 1m away from the corner. Above, this can reduce the interference of standing waves. You can also put the subwoofer on both sides of the best listening position and keep the proper distance, because the human ear does not have the directionality of the subwoofers from both sides. Sensitive, so the subwoofer will not interfere with the original sound image localization of the front three channels. Of course, the best placement position should be determined by experiment. The method described below may be helpful for finding the subwoofer. The best position. Put the subwoofer in the best listening position (temporarily remove the nearby debris), connect its speaker cable and play a piece of music with strong bass effect, then listen carefully around the room. When the ear is attached to the ground, it is roughly at the height of the subwoofer. When listening, find the most stable, deepest and clearest point of the bass, which is the best position for the subwoofer.
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