【 Weak current College 】 broadcast speaker selection and configuration

1. the selection of the radio speakers

In principle, should be considered as environmental selection of different varieties and specifications of the radio speakers. For example, in a ceiling, ceiling-mounted indoor, use embedded, not the back cover of the ceiling speakers. The speakers structure simple, relatively cheap and easy construction. The main disadvantage is that there is no back cover, susceptible to insects and rodents bite. The only frame ceiling without ceiling Interior (such as the u.s. market), expressing the hoisting-and-tube-type speaker or rear cover of the ceiling speakers. Since the ceiling is equivalent to an infinity of baffle, so there is a ceiling conditions the use of the back cover of the speakers also does not cause sound short circuit. But when there is no ceiling is very different if you continue to use no speakers back cover of smallpox, the effect is very poor. This principle should use hoisting speakers. However, if such investment is large, you can also use the back cover of the ceiling speakers. Have the back cover of the back cover of ceiling speakers not only general mechanical protection and, to a certain extent, to prevent the role of sound circuit.

In ceiling-mounted indoor (such as the underground car park), to choose wall-mounted speakers or indoor sound columns.

Outdoors, use outdoor sound columns or horn. This type of code string and Horn is not only waterproof function, but the volume is large. Due to the spacious outdoor environment, no reverberation effect, select the volume for a large variety is necessary.

In the garden, lawn, use grass speakers. This type of speaker waterproof, beautiful, and the volume and audio quality are very high.

The decoration is fastidious, ceiling high wide Hall, use elegant, tonal harmony of hoisting-and-speakers. In the fire safety requirements are relatively high, the use of fire-speakers. These speakers are sealed type, its outlet port matching withflame retardant casing.

2. configuration of the radio speakers

Radio speakers, in principle, to the principle of uniform, dispersed in broadcasting service area. Its decentralized level should ensure that the service area of signal to noise ratio is not less than 15dB.

Typically, advanced Office noise floor of the corridor is about 48 ~ 52dB, Super shopping centre about the noise floor, 58-63dB downtown section of background noise about 70 ~ 75dB. Considering that in the event of an accident, the site may be confusing, so the need for emergency broadcasting, even if the broadcast service area is Office, nor should the background noise estimation too low. Made sure of this, as a general consideration, in addition to the bustling lively places, it may be more or less the background noise as 65 ~ 70dB (except for special circumstances). According to this projection, radio coverage of the sound pressure level to more than 80 ~ 85dB.

In view of the radio speakers are usually distributed configuration, the broadcast coverage of the sound pressure level can be approximated as a single radio speakers. According to the theory of electro-acoustics, speaker covering area of the sound pressure level of sensitivity SPL with speakers-LM, fed to speakers power P, listening points and speaker distance r, the following relationship:

SPL=LM＋10lgP－20lgrdB（1）

Ceiling speaker sensitivity level in 88-93dB; rated input power: 3 ~ 10W. To 90dB/8W calculations, close to the speaker of the sound pressure level at 8m about 81dB. The above calculations are not considered early reflections group contributions. Indoors, the early reflections and the adjacent speakers contribution will enable the sound pressure level increase of around 2-3dB.

The approximate calculation based on the above, the ceiling is not higher than 3 m venue, ceiling speakers generally can mutual distance 5 ~ 8m uniform configuration. If you only consider background music regardless of the emergency broadcast, you can increase the distance to 8 ~ 12m. In addition, applicable to the Chinese mainland's fire radio design installation specification (hereinafter referred to as "specifications") there are some mandatory: "corridors, halls, restaurants and public places, speaker configuration number, should be able to guarantee that any part of this layer to the last speaker walking distance not exceeding 15m.

The intersection in the aisle, the corner should set speakers. Aisle at the end of the last speaker distance from wall is not greater than 8m ".

There was virtually no outdoor places early reflections group, a single radio speakers effective coverage can only take the floor above calculations. Due to the lower bound of the corresponding distance is short, so in principle should be used by multiple speakers consisting of allweather. Fed to speakers groups (for example allweather) signal power each doubled (provided that the group could accept), sound pressure level can enhance 3dB. Please note that the "times" has the meaning assigned to it. From 1 to 2 is doubled; and 2 shall be increased to 4 is doubled. In addition, the distance each doubles, sound pressure level decreases 6dB. According to the above-mentioned rules is not difficult to project the outdoor sound column configuration. For example, to CS-540 outdoor sound columns, for example, its rated power 40W, is a single ceiling speakers of more than 4 times. Therefore, the effective distance covered is greater than a single ceiling speakers 2 x. In fact, this distance can also be larger. Because the sound column of sensitivity than individual ceiling speakers to high (about 3 ~ 6dB), while each additional 6dB, distance can be doubled. That is the 540 allweather can amounting to 20m distance covered. But the sound column of a narrow radiation angle, only its right in front of about 60 ~ 90 ° (horizontal) or so. The specific calculation is still available-(1).


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