Ultimate Studio Home Theatre

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Acoustic treatment of the room (added)

Acoustic Sound proof rooms or acoustically dead rooms must have the largest possible dimension and large cones on its walls. Such, literally, fantastic constructions, only a big company or scientific research centers and institutes can afford. For the required first-class reproduction of sound material such conditions are not necessary and the price and size of such a project is huge. Listening to music itself in a condition of sound proof room has no meaning, because the task of such premises is strictly fulfilling the conditions, needed for precise measurement of amplitude-frequency acoustic characteristics at frequencies lower than 300 Hz. In case of quality sound reproduction it is necessary to exclude the possibility of the room characteristics influence under 500 Hz and secure additional satisfactory standing waves low frequency level of absorption. An ideal linear amplitude-frequency characteristic at low frequency level is not necessary, because in the case of acoustic treatment of rooms deviation will be very low and the remaining resonance is possible to correct with equalizer.

Dimensions of rooms, necessary for quality sound reproduction, it is easy to determine. The main factor is the screen. Suppose that there is a maximum Cinema configuration class Ultimate Studio with projector and main monitors. If width of the screen is 4 m on that size we should add one meter more on each side because of acoustic systems. Speakers should be placed on the principle of one-sided triangle. Distance between acoustic centers of the acoustic system to the listener should be equal the distance from each speaker separately. In other words, acoustics should be placed at an angle of 30 degrees. However, if there is a big screen, the distance to the listener can be larger than the distance between speakers. Using a projector and large screen opens the possibilities of cinema with smaller dimensions. For this reason it is not logical to use such a system for the individual cinema projection, but for the group of 9-16 people. According to this, the one-side triangle should coincide with 25-30% of length of cinema seats. Furthermore it is necessary to determine the zone of sound wave freewheeling. Its width equals the sum of the screen width and sound box dimension, the length – from speaker to the last row, while the height is measured by the vertical dimension of the screen or acoustic system, if the height of the acoustic system is bigger. At picture below that zone is marked with inner red rectangle. It is forbidden to place an object that reflects sound (tables, shelves, bare floor, technique ...). Even the armchairs are objects that reflect sound but they are necessary.

Then it is necessary to apply the basic rule of acoustic system configuration, which is based on alienation of the surfaces that reflects sound from the zone of sound waves freewheeling at the distance of 2 meters on each side. Thus, acoustic systems will be at the same distance from all surfaces in the room. Bigger distance is not necessary, because in the case of quality sound absorption it will have no effect. Equal distance is simply not needed. The most important thing is that the walls, floor and ceiling, in a relation to the acoustic system and the listener, are in a distance no less than 2 m. In the end, real dimensions of the listening rooms, which are shown in red rectangle, derived by summing the length, width and height of previously determined zones of sound waves freewheeling and that is four meters (two on each side). We should not forget that the acoustic system, screen and the audience will be on two meters height in relation to floor.

I mentioned earlier, that the quality sound reproduction requires minimum area of 100 square meters. We can get those dimensions just analyzing the above stated terms. The exact look of the optimal space intended for listening to music and watching movies is shown below.

Dimensions of the room marked with red triangle are in fact, free space, which does not include room filled with material that absorbs sound and supporting structures. In that case it is necessary to count standing sound waves that are not present in the normal listening rooms. Although it may sound strange, the zone of the sound wave freewheeling equals the proportion of standard living room.

A more detailed calculation dimension of the space of the cases above is described below:

Length: 2 m is the distance from the wall to the speaker, 1 m is the width of the loudspeaker; 4-5 m is the distance to the audience (center or the first row), 3-4 m length of the rows, 2 m distance from the backrest to the wall. 12-14 m, total.

Width: 2 m from the wall to the left speaker, width of the left speaker-1 m, 4 m wide screen, right speaker -1 m, distance from the right speaker to the wall-2 m. Total, 10 m.

Height: 2 m from the floor to the lower end of the screen, screen height 2.25m, 2 m distance from the top of the screen to the ceiling. Total: 6.25 m.

Real space capacity is 750 cubic meters. Surface for acoustic treatment is 515 square meters.

Now it is necessary to apply materials that absorb sound. The first are the cones which are made of sponge of medium hardness, after that follows a thick layer of porous absorbent wool type. The main problem, which is odd, is the cones. Most of them have height of 10 cm and therefore their application at the huge space with a powerful acoustic system is meaningless. For effective low frequency sound dispersion it takes cones with a minimum taper length of 20-30 cm (ideal 1 m), which can increase the cost of meter of such material up to 40-80 Euros. Considering that it is necessary to treat the area of 500-600 square meters, the value of such acoustic treatment can range from 20,000 to 50,000 Euros. The way out from that situation will be the use of ordinary black soft sponge, low density, in the form of sheets. That type of sponges is usually used for making the soft sponges for dish washing. Black color is required in order to avoid light reflection from the surface of the room during the projection. This sponge has a very low coefficient of sound absorption, so it partially passes through its structure the whole specter of sound waves, to a next basic level of sound absorbent. Such a soft wall will absorb High and medium frequencies and low frequencies will pass through the next layer.

After a cone or a layer of sponge, it is necessary to apply high-quality sound absorbing material. It must have maximum sound absorption coefficient in the whole range of human sense of hearing, but at the same time it cannot have high price. For this purpose it can be used any building thermal insulator like glass, mineral, basalt or some other wool. These materials have almost the same sound absorption coefficient in range 0.7 - 0.95. The best material is basalt super thin fiber that has few characteristics: it is a bit expensive, it has no decay process, it’s a bit sticky, it has no phenol basis and most important that is environmentally safe. I must emphasize that that material cannot be creased, because in that case a large part of low frequency particles is reflecting back into the room. Usually material like sheet can be creased and Rulon have an appropriate level of required pressure. Building thermal insulators fully absorb medium and high frequencies. The main problem is the low-frequencies, which have no direction but have a large amount of energy and they reflect form he surface of the material or the wall behind them. Because of that they have to be of porous materials instead of creased materials because they enable leak of low frequency energy to its deepest layer. The thickness of such material should be 50-100 cm. A layer of sponge, in this case, has a role of a specific filter, which prevents the process of decoying and inhalation of insulating material particles to the human respiratory system. In that case Additional layer can be fabric which density is between the cotton and the sponge.

But that is trifle. The most important thing is the parcel where you can build all of that, because if you don’t have it you can question yourself where will you put your Ultimate Studio audio system? This is a common problem of people who live in a big city it where the parcels with all necessary communications are very expensive. Their price overflows not only the price of audio and video equipment, but also the construction of the facility and that's the only obstacle.

But the situation isn’t so bad, as it may looks. In the text above a maximal version of room for listening has been described, but it can be more compact. If you don’t have a need for a large number of seats, you can limit the space with a single row of seats or sofa and In that case the premises will be more rectangular than square. Even the distance from the speaker to the wall behind can be shortened to 1m and the dimensions of cinema screen can also be reduced. In that case the huge room can be reduced to the dimensions of the garage or maybe a wooden cottage with dimension of 6x6 m.

If you are unable to overcome the size of your apartment the home cinema should be placed in the largest room. But you will be satisfied if the size of the room is 20 square meters. That enables the use of acoustic systems with 12“lowtones and more or less decent panorama of sound and low frequencies. Acoustics of the Ultimate Studio class can merely but still be adequately installed in those conditions. Into the room you can put a Stage Accompany or handmade TAD sound boxes with small low tone speakers. We can also take into the consideration JBL Everest surround set of speakers which has three-way system structure and beryllium membrane. The criteria and principles of acoustic treatment are the same, as in the maximal version, but it is most likely that you can’t apply on a wall a layer of material thickness of 10-20 cm, because the increase of thickness reduces the already small room space. If you are using regular 8 "low frequency speakers on 80Db for peaceful listening to music in a standard room, the thickness of the layer of material in the region of 10-20 cm is quite enough. But if you use a compact version of the Ultimate Studio acoustics with 12 " low tone speakers as cinema sound system, where the dynamic is 10 dB higher , the layer of the material thickness 10-20 cm is not enough. In a small space is the preferred to use of cone height to 5 cm. Such a limitation is related to the fact that the cone is partially spreading the sound and it has a smaller sound absorption coefficient than quality sound absorbing materials. It is also possible to remove the cone completely. In that case sound absorbing material must be of better quality, like basalt super thin fiber. Keep in mind that one and the same material can have different characteristics depending on the specific delivery series.

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