Home cinema

20120704-ACERN-26

  • Idealy, for home cinema have to be a special room. Special connoisseurs of cinema often build a room specially for home cinema. Room geometry in that case pays off specially under a certain audiosystem, which will be established indoors. And acoustic optimization of a room is carried out very serious. But in this case a room area often exceeds one hundred square meters. But first of all it is necessary to tell about a starting point. That is about, how speaker systems of home theater should settle down in a room if to observe all rules. There is a large quantity of possible combinations, describe even a part simply impossible. And on this, we can offer two methods of solution of this subwoofer installation problem:

    1. Play any musical composition with an accurate and expressive bass (for example, which has acoustic contrabass) and start to experiment: put a subwoofer in any place of a room, sit down on in advance defined place of listening and listen. If a bass accurate, pure and not hooting, if you hear not “porridge” and “roar”, namely a contrabass, then you can leave a subwoofer on that place and rejoice that experiment successfully and quickly ended. If a bass does not suit you – continue to try to put a subwoofer in other points of a room and to listen to result. It is not excluded that it is necessary to make small shift of furniture in a room….

    2. Second option is called “by contradiction”. It is simpler, more effectively also takes away less time. But remember that bass in test musical composition should be as much as possible enduring and monotonous on sounding, after all you should mix up on a room at height about 30-40 sm from a floor. So, put a subwoofer on that place where you assume to sit during cinema viewing. Include a test track and begin without hurrying to mix up on a room. The purpose of this action – to find that place in a room, where bass of working subwoofer will be the most comfortable and correct. Then put there a subwoofer.

     

    Further we provide information only about main channel installation – full-band speaker systems of face-to-face channels, rear channels and central channel.

     

    If imagine that all speaker systems are absolutely identical, acoustics of a room is also ideal and there is an empty seat, placing of speakers should be done, looking at this scheme. In this case a model of arrangement of system for work of a complex on the scheme 5.1 (five channels, one subwoofer) is described. At such arrangement of audio systems are made multichannel soundtracks correction to films in modern studios:

     

    Center and front pair are located on lines of the virtual circle, which radius is the distance from listener to central audio system, and circle center – head of the listener. Distance from listener to each front audio systems and central to audio system are equal. Distance between front audio systems equally to distance from listener to each of audio systems. Rear channels are located on the same removal from listener (also on a virtual circle) at angle about 110 ° to axis «listener – screen».
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    In this case all possible discrepancies of artificial delay are minimized. In theory all channels are absolutely equivalent both on loudness, and on sound reproduction that is necessary for us in real home cinema.

    In practice all discrepancies at selection and placement of audio systems can be compensated by AV receiver or AV processor electronics.

    On following scheme is shown an ideal placement of audio system in home theater, working with 7.1 sound.

    In this case rear audio systems not 2, but 4 – two of them are located strictly on each side of listener, and two others – behind.

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    So, if possibilities and situation allow, at arrangement of audio systems in home cinemas is necessary to be guided by these two schemes of placement (for 5.1 systems and for 7.1 systems) , because they are referenced. Only do not forget about acoustic treatment of the room- it is very important detail at home cinema construction. And treat it very seriously as bad acoustics of room with ease will spoil a sound even competently picked up complex.

  • If try to construct 5.1 home theater according to reference scheme, it will look approximately here so:

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    If you have a desire to construct a cinema not only for two-three people, and arrange viewing by all family or with friends, that logical solution will be simple to put some more chairs. However, there are some nuances. For example, place all sitting persons thus is not recomended.

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    Main reason is that sitting listeners along the edges will be out of zone of balanced sound field (green zone in drawing), because will feel an obvious imbalance of cinema channels: next rear audio system literally will “beat” in ear, and most distanced from sitting in an side chair of front speaker practically will not be audible. In view of that, the effect of presence in thick of things completely will be gone, and there will be no pleasure from viewing.

    Place everyone correctly is possible, having put a sofa and chairs as follows:

     

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    If room, where the home cinema is established, has an area about 25-30 m², one pair of rear audio cannot capture all sitting (place in such room more than 5-6 people does not recomended) – in this case it is extremely desirable to establish second pair of rear speakers (as on scheme). Each pair of rear audio systems will work for a certain zone (in this case, for one row of sitting people) – just like that happens in big cinemas: in a hall is set a big number of rear audio system channels so that each sitting did not feel an imbalance of channels in system.

    But if your room of listening has an area of 40 m² and more, create a correct sound field for all sitting (up to 10 people according to scheme «3 rows on 3 chairs») can be done with one pair of powerful audio systems, after all speakers will settle down on decent removal from sitting, so their sound will manage to extend more widely.

    If try to construct home cinema 7.1 according to reference scheme, the system will look approximately so:

     

    room-1-71

    Besides, in case of desire to equip theater for 5-6 people, it is possible to use additional pair of lateral audio systems of surrounding sound (will be one pair of rear speakers). If a room rather big, it is possible to use reference scheme of placement for 7.1 systems (drawing is higher). As in case of creation 7.1 systems according to scheme with two pairs side audio systems of surrounding sounding (as in drawing below) it is necessary to displace slightly first pair of lateral audio systems of surrounding sounding back, concerning the first row sitting, and coordinate loudspeakers of this lateral audio systems on the first row (as on scheme below), differently the audience of the second row will hear a sound of first row lateral audio systems, so that rear speakers of the first row will appear for sitting in the second row ahead, and, therefore, will cease to be rear – it will turn out not so well as many effects will be reproduced not absolutely correctly.

  • In absolutely small rooms the most widespread scheme with a TV arrangement at one wall, and a sofa – strictly opposite. It is the most logical scheme from reference point of view. However, many people try to squeeze in a zone of effective scoring more pair of chairs, as, for example, in drawing:

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    It is not recommended to do like that.

    Same reason: sitting in outer chairs will not be in «green zone» (therefore there will be no pleasure from viewing), moreover, rear audio system will block themselves. So the most correct scheme of placement is a considered if a room has an area of 10-20 m².

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  • Very often meet a situation when home cinema try to put according to diagonal scheme. We want to note that it is very unsuccessful idea.

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    At such arrangement of listeners create a correct sound field is possible only for one person sitting in angular chair. Simply in attempt to hang up rear audio system widely to capture all sitting, situation when for sitting in angular chair rear audio of system will appear ahead will turn out, and sitting on a sofa all the same will hear an appreciable imbalance of channels. So there will be «a theater for one person»

     

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    Thus, it is extremely desirable to carry face-to-face audio of system a little in the parties to observe a principle of an equipotential triangle (see reference scheme )

    At desire, instead of chair can put a sofa – in this case two or three can take pleasure watching a film, but then rear audio system should be hung up a little more widely. Remember: it is desirable to observe a 110 ° corner for rear audio systems (see reference scheme ).

    Here examples of absolutely incorrect placement of audio system complex.

     

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