【 Weak current College 】 room decoration ([ninth article] on the establishment of domestic audio-visual room)---Power By 【 China power house network 】

A complete home theater is composed of audio-visual equipment and audio-visual room, room audio response characteristics and equipment of the frequency response metrics are equally important. United States Audio magazine once said, the formation of a high-quality home theater must not be such as the DOLBY, THX certified a/v equipment to buy to get connected. In introducing the THX home theater, it often use a lot of space to describe the construction home theater at the time how to retrofit room 3D dimensions and processing audio-visual room wall, floor, ceiling, Windows and doors, etc., as well as how to properly place the loudspeaker, screen, etc., and audio-visual equipment inventories, indexes, etc. are just a few Liu Liu. In fact, many friends also spent a lot of human, material and financial resources in audio-visual equipment in the frequency response, distortion, and other indicators, but ignore the room's 3D dimensions, interior decoration, forms and materials, home furnishings, etc. to listen effect of great impact, the expense to the construction of the effects of unsatisfactory home theater. Hi-Fi enthusiasts often speak of "master playing room, low hand play equipment".
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As an audio-visual room, must have a good acoustic properties, such as the reverberation time, resonant mode, sound Contracting State, the acoustic field uniformity, etc. These indicators and three dimensional dimensions and room wall, floor, ceiling, and other material and texture interface speaker set-up are closely related. First, an audio-visual room acoustic requirements
This is also known as hardware requirements. One room has length, width and height 3 sizes, in each direction has a minimum resonance frequency. Room actual minimum resonance frequency is determined by the length of the room, its wavelength is equal to two times the length of the room. As a long as 6m room, when the speed of sound as 344m/s (at room temperature 20 ° c), the lowest resonance frequency in the room is approximately 29Hz, which is in the room have the lowest effective sound frequency. Even audio equipment cannot be given below the lowest resonance frequency of the sound, but in the room, could not form a half-wavelength, not meet the conditions of the resonance of cannot produce a resonant, nor sufficiently effective sound pressure, therefore, to best effect. The room of three-dimensional decided there are three basic intrinsic resonance frequency and with three basic intrinsic resonance frequency into integer multiplication rate of harmonic exist, these acoustic wave propagation in the room, when mutual interference produce complex assemblages resonant frequency. From the acoustics, the room can be seen as a resonator frequency when the sound source and the decision by the room three-dimensional natural resonant frequency (normal rate) will form a standing wave resonances produced, this is the acoustic resonance phenomena. Audiovisual room sound field uniformity, acoustic colouring and frequency of irregularities are concerned with the acoustic resonance. This kind of resonance will give the original signal with the room acoustic resonance of color, resulting in the sound. General performance in low frequency a segment or a few paragraphs frequencies loudness excessive strengthening, "humming", resulting in the frequency band signal replay loudness imbalance, serious will significantly affect listening. As for the high frequencies of resonance is more evenly distributed, sound less dyeing, sufficient to affect the overall listening effect, so the focus should consider the effects of low frequency resonance. In order to avoid or reduce the unwanted sound dyeing, the resonance frequency of the uniform distribution, avoid prominent isolated a segment or a few paragraphs frequency resonant mode, one approach is reasonable change room 3D dimensions. You can consider the adoption of appropriate internal decoration, production of partition wall and ceiling or even removed certain non-load-bearing walls and other methods to change the 3-d dimension (such a reasonable modification to take into account the structural safety factors, such as intention to remove a section of wall, it is best to ask building professionals). Simply speaking, this is when you select the internal loudspeaker design three-dimensional principle is consistent, that is, length, width and height cannot be as integer times or too close. Specific acoustic resonance mode, the calculation formula and the data no longer lay down, if necessary, refer to the acoustic books. This provides an organized by the International Electrotechnical Commission (IEC) reference European family room by IEC29-B family room standard for reference, as table 1 and Figure 1. Another method is more reluctantly, that is, you can keep the original 3D dimensions unchanged reasonably layout, use the appropriate sound-absorbing materials to enhance the walls, floors, making the interface damping of a frequency resonance reduction of strength, the resonance wave flattening, wide, thereby reducing harmful resonances to the overall sound. But this method effectiveness is limited, only applies to less harmful resonances strength. Because if you want to reduce the strong resonance and keeps strengthening the harmful sound absorbing materials, but also makes the reverberation time is greatly shortened, the same will be listening to interested worsening replay sound effects become sleepy, lack of color and angry. 2. audio-visual room reverberation time this is an audio-visual room, another important parameter. Reverb is determined by the room sound multiple reflection characteristics, which make the Interior of the sound pressure in sound source stop voice still continue for a period of time. Reverberation time refers to sound sources stop play indoor sound attenuation 60dB sound pressure, i.e. down to the original sound pressure stability values of the millionth time. Audio-visual room reverberation time if too long, the sound source in front of the sound has not disappeared behind the sound appeared, easy to make bass, language on the roaring, etc. are concentrated in the high frequency band signal clarity decline, even a sense of direction to disappear (because sound like positioning is on the left and right main speaker in the high frequency of direct sound and reflection of sound mixing too much lag from multiple directions, direct interference effects of sound, direct access to sound like the correct location). If reverberation time is too short, you will make the sound becomes thin, dry, dull, lack of color and angry. Just the reverberation time is moderate, the overall sound will appear full, lively, and wealth to the appeal and expressiveness. The best reverb time strictly speaking is not a fixed value, even if it is specific to a room. It is based on the individual's subjective experience and experiences, and enjoy a variety of program types desired reverberation time is different. Enjoy television programme the reverberation time requirements are slightly shorter, and sound effects will be more vivid, character dialogue, or sound like positioning. And enjoy the program you need a little chunyinle long reverberation time, this sounds can feel "more comfortable", in which classical music program requirementsReverberation time than pop music a little longer. This is because different types of programmes produced its late mix various demands differ, replay also need corresponding moderate reverberation time in order to make sound effects to get high definition restored. As a family room, generally take a compromise to deal with the reverberation time, and then open or the surface of the walls of the curtain, or adjustments as part of the tapestry. A very large number of trials and information points, usually the family audio-visual room reverberation time normally take around 0.4 ~ 0.6s (500Hz) more appropriate. Calculation of the reverberation time is typically use the following formula: t = 0.16 V/α, where t is the reverberation time, seconds; V is the volume of the audio-visual indoor units of cubic meters; α is the total absorption coefficient. Table 2 is commonly used for sound absorption coefficient of sound-absorbing materials. For example, an audio-visual room long 6.2m, width, height 2.8m 4.4m. Ceiling and floor are flat, plastering, the ground floor there is a middle 4m×3m's chemical fiber rug, the hanging on the wall on both sides of a piece of velvet curtain 6m×3m (off the wall 1cm), opposite the screen wall has the chemical fiber rug 4.4m×2.8m. Try to estimate the audition room reverberation time (500Hz Department). Discerned from table 2, bare walls, floors of sound absorption coefficient α 1 0.02, curtain wall 1cm hoisted α 2 0.44, carpets of sound absorption coefficient α 3 0.28, the total absorption coefficient:
Α total = 1 × 4.4 × 2.8 × α 1 + (2 × 6.2 × 4.4-4 × 3) × 2 × 1 + α 6.2 × 2.8 × α 2 + 4 × 3
×α3＋4.4×2.8×α3＝23.184
Audio-visual room net volume: V = 6.2 × 4.4 × 2.8 = 76.384m3 then
Reverberation time: t = 0.16 V/α total = 0.16 × 76.384/23.184 = 0.53s can tell, this audio-visual room reverberation time is appropriate, if you consider the audience and the furniture is sound-absorbing elements of reverberation time will be slightly shorter. 3. speaker set-up when you spend a lot of effort and a lot of money to audio-visual room as some requirements mentioned above, if decoration sound set-up is not appropriate, then the result is only 4 words: "wasted". The purpose of establishing an audio-visual room is in order to better appreciate the authentic sound effects, and Hi-Fi appreciation has a lot in common. About the speaker set-up here only briefly some of the more principled considerations. First of all requires audio-visual room left space acoustic characteristics should be symmetric (not necessarily the Visual symmetry), that is, left and right sides of the space of sound reflection or absorption capacity equal to as much as possible. Two main speaker distance typically require more than around the main 2.5m or sound box and the angle between the audio-visual are greater than at least 30 ° (chunyinle enjoy best angle is 60 degrees, and home theater sound like to consider coordination, General requirements in 45 ° left-right), to get the better of three-dimensional sound field, but the distance or angle can not be too large, otherwise it may cause the image and sound like positioning. If the screen left or right orientation of the Department of acoustics, as far back as the screen is beyond the scope of the approximate reasonable cause hearing and vision. Audio-visual room acoustics to a certain extent and location of the sound in the room there is a direct relationship. The main speakers in the room the location of the main feeling to decide according to audition. The main speakers in a corner, leaving the wall of a distance or away from the side wall, and many other locations audition, select one to get a homogeneous sound field place the main resonance box. In addition, then appropriately main speaker backwards a few angles as well as the main speaker pad the high number of listen look effect is better (sometimes this change would, obviously, can get pretty good results). For surround sound box directivity characteristics of less, their specific placement is not very strict, generally on the left and right side behind the audiovisual ', but not too close to the audio-visual, speaker height should be higher than the human ear. Two surround speakers between is slightly smaller than the main general speaker of spacing. When the surround sound box put in place, the General need for AV amplifier surround delay adjustment so that the front and rear speaker sound seamless, perfectly, the satisfactory overall effect. Central speaker set-up some relatively fixed, and the screen Center in the same vertical line, it is best to make the main speaker, high-pitched sound of the speakers and audiovisual ' ear in the same horizontal level. If the conditions are not met, in treble and master speaker treble speakers the best high and low gap does not exceed 30cm. If the difference is too great, the main speaker and sound in speaker like height will obviously not consistent, causes the screen like a moving body of sound becomes cluttered, very natural, audio and video effects. Also worth noting is that when you select one of the speakers, the treble speakers use the same primary speaker. This will enable the Central speaker and main speaker in the frequency response curve, directional, phase on better match, this is also consistent with Dolby AC-3 and THX for basic technical requirements. Subwoofer is commonly known as "subwoofer", because it is responsible for the frequency is generally concentrated in 120 ~ 150Hz following, so it's in the placement of the audiovisual room will pay special attention to choose, be sure to put indoor multiple locations to audition, select one can minimize the distortion sound with and where to place it. Generally speaking, the subwoofer is not placed in the corner, close to the wall or audio-visual room Centre, because these locations are easily aroused strong resonance. In fact, this article pointed out that several aspects of the above is a more "popular" principle. But everyone has different tastes, there are enjoying various practical furniture, room layout, or even different structure of speakers also have different placement requirements, so that home theater building, decorating is a personalized, "and" the system should be done.