My goal is to create a home theater space with great sound and video effects within the range I can afford. Although my budget is not high, I would rather spend more on equipment investment. Enjoy the vivid effects brought by high-quality cinemas. Every time you watch, you will be very happy. It turns out that I have the right choice when investing like this.
I will go into detail about design options for equipment, room building, home theater wiring, air conditioning installation, and storage.
Room <br> As mentioned earlier, my home theater audio-visual room is opened by a small bedroom with a storage room adjacent to it. The place is extremely narrow. I closed the outdoor-facing window in the small bedroom, and I added a plasterboard to the concrete wall of the storage room. Because it is connected to another bedroom, in order not to affect the rest of the family, I simply made a sound insulation treatment. It is a cavity distance between two layers of gypsum board with a staggered keel structure, which is added to the home theater of the keel. With a double-layered gypsum board, the treatment basically does not penetrate the cement wall to affect the rest of the family next door. This method is suitable for the sound insulation of cinemas in general home theaters (decibels no larger than 90). The cost is cheap and the professional sound insulation materials can not be used.
The small space that is prepared as a theater is actually very unfavorable for acoustic processing in terms of size ratio, and his length and width are almost multiples.
In this way, the standing wave resonance of the long and wide parallel faces is caused. In order to solve this problem, I designed two sets of storage cabinets that can occupy the entire width and are respectively placed on the front and rear walls. This can effectively serve the standing wave of the parallel wall. The wooden cabinet made of high-quality wood will have a good effect on the standing wave, but the cabinet has a certain thickness, and the opening size and depth are also very particular. There are times when you don't need to use professional acoustic treatment products. General furniture can also play a role in diffusion. But if you use those furniture to adjust the sound field, you must have an expert to guide you if you have a few necessary situations.
Although it was a small room, I also used a double door to increase the width of the room, which made it easy to move some furniture and equipment into the room. In order to maintain the aesthetic effect of the overall home furnishing, the double door is made of glass. I used a thick curtain made of French chenille in the inside of the audio-visual room and added a blackout cloth. This kind of curtain not only effectively shields the light, but also eliminates the direct reflection of the sound waves brought by the glass on the door.
The room was painted in a more natural medium-gray with a little blue, and the ceiling was a darker color. The color scheme was progressive. In fact, the color used in a home theater does not need to be strict. Sometimes, in order to pursue the contrast of color, it is necessary to make the color of the room darker. The one I don't object to, but I have to grasp it myself, because that color After all, people staying inside are not comfortable. The two walls are curved with sound-absorbing columns for sound absorption, and the ceiling is also equipped with sound-absorbing blocks around the projector.
The concrete floor is covered with a thicker carpet, and a thicker floor mat is added under the carpet.
Acoustics <br> I have seen many home theater renovations, and I have experienced the effects of several of them. There are many home theater designs that are eager to absorb sound and make too soft bags. This room sounds dead and makes people Very uncomfortable. The effect is not very good to absorb too much low frequency. For the acoustic treatment of small rooms, the sound absorption area should not exceed 40%, and the position of sound absorption needs to be strictly controlled. The area of ​​the first reflection sound needs to absorb sound energy.
There are three typical acoustic problems in a typical small room for use as a home theater. They need to deal with the resonance of the room, that is, the standing wave, as well as the oscillating echo of the parallel wall, the reverberation time, and a certain degree of echo.
Bass Resonance - standing waves that can result from parallel walls and parallel floor/ceiling. Bass resonance - continuous sound waves can be caused from parallel walls and parallel ground/roof.
Reverb Time - the time required for any sound to decay in the room. Response time – the time required for any sound to decay in the room.
Reflections - direct reflections off of walls arriving at the listening position within 10ms of the original sound. Reflection - the original sound that is reflected directly to the wall and then to the auditory position between 10 meters.
Sometimes people are overly convinced of the effects of acoustic processing. In fact, acoustic processing is just an adjustment to eliminate bad acoustic effects, but those bad effects are mainly from poor room proportions, so if you choose one from the beginning A good proportion of rooms are used as home theaters, which saves a lot of input costs while getting good sound quality.
Our current rooms are all reinforced concrete walls and the area is not large. Because of the hard reflection of the sound, the reverberation and echo in the room are very serious. At the same time, the proportion of the room is relatively regular, and it is basically square. The standing wave of the room is generated, so the sound will be "rumbling" without any level, and the dialogue of life is not clear. If you use karaoke equipment, there will be a lot of howling. Our goal is to adjust the sound absorption and diffusion treatment of the room to reduce the reverberation of the room to the reverberation required by the theater, that is, the reverberation is 0.3-0.4 milliseconds (at 500 Hz). In this way, no matter what kind of sound pressure level sound does not sound, it is very dense, and has a good sense of layering. At the same time, we set the low-frequency trap and the diffuser according to the measured room standing wave frequency band, which is the sound field effect of the sound is more natural.
Bass Resonance <br> Bass resonance is the toughest problem that home theaters must deal with. We have just said that many rooms in a typical house are rectangular and have a flat roof (parallel to the ground). This will result in an amplification of the acoustic energy or an increase in a certain bass frequency (the wavelength is a multiple of the room dimension), with the result that one of the bass bands is particularly prominent than the other bands causing the tone to be dyed. The worst case is that such low-frequency features appear a lot, and resonances appear on many axes, when standing waves appear.
In the initial construction, my room had a very serious bass resonance problem. The length of the room is almost twice the height and is close to the width. I was able to reduce the problem of bass resonance by reducing the length of the room by adding cabinets behind the room (from the ground to the roof, from the wall to the wall) and behind the screen.
The front cabinet is actually a low frequency trap. Used to absorb the resonance of a specific frequency of bass energy in the room.
The end result is a smoother bass energy, especially in the seat position that sounds smoother.
Reverberation time <br> Reverberation time is the rate of sound attenuation. There are a large set of professional definitions that are not detailed here. For us, a room with too short reverberation time will be very dry and inanimate. The room has too long a response time that will make the sound turbid and unclear.
Many people ask what is the best reverberation in the room, this is not necessarily the case. If it is purely used for theaters and the power of the equipment is also large, the reverberation time is small, but the power of the equipment is relatively small, and there is a certain reverberation to amplify the sound.
The basic test for reverberation can be experienced using the method of high-five, and the high-figure test provides a lot of acoustic information for an experienced acoustic engineer.
Reflections, images <br> Sound reflections on walls and other objects in the room can reduce the characteristics of details and images. There are two types of sound reflections – those that can be distinguished from the original sound and those that cannot be distinguished. This is the first reflected sound and the second reflected sound.
The first reflected sound cannot be distinguished as the most harmful sound quality. This is because these reflections confuse the human auditory function causing the positioning to be blurred. The closer the time is, the closer the reflection will be to the original sound, causing a worse effect.
The longer delay reflection energy actually helps the air to feel the sound as long as the reflected wave energy is not too high compared to the original. Those reflections in the room will spread into your ears. But if your seat is 5-6 feet from the back wall and the back wall is smooth, you might want to consider adding some diffusing devices (or even some bookshelves) to help reduce the intensity of direct reflection for this wall.
I didn't worry about the side of the short reflection or the wall behind it. The absorption control panel reduces the energy of short reflections on those walls, but at the cost of reducing reflection time and making the room silent too dead. But although the speakers are closer to those walls, I meet the image and the superior sound in other ways.
I decided to use a diffuser (RPG BAD control board) on the side wall just below the rear speaker. This reduces the reflection directly from the opposite wall horn.
Applications:
The Grounding Transformer is a kind of auxiliary transformer that used to offer an earth point for the Delta-Star system. They are typically used for providing a path to ground for unbalanced load current and for fault currents on system where a suitable ground is otherwise not available.
Design:
The grounding transformers are generally designed with one of the two configurations: Zig-Zag (Zn) with or without an auxiliary winding or a Wye (Ynd) with a delta connected secondary. The Zig-Zag connection is preferred as it is more cost effective and have smaller size than the Delta-Wye unit. For more safety, neutral earthing resistors (NER) are often used in conjunction with the grounding transformer to limit neutral ground fault current magnitude. The rated voltage of the NER should be equal to the line to ground voltage of the grounding transformer. The current rating and duration should match the grounding transformer
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