【 Weak current College 】 school athletic field broadcast sound reinforcement system design

School outdoor track and field-field sound reinforcement, mainly to meet the meeting, the games, broadcasting gymnastics, language and music sound reinforcement, it is different from normal room sound reinforcement, and from outdoor concerts, sound reinforcement, but instead has its own characteristics. Here to talk about this issue.
To design an outdoor athletic field of broadcasting sound reinforcement system, we must first understand its venue size and choose a viable sound field layout scheme, to a lesser extent, depending on the sound field layout scheme to choose the right speaker, to the extent possible, select low attenuation of long-range sound kinds. Because as the school athletic field sound reinforcement systems, investment limited, technical standards will not be too high, we are here not to discuss the network audio system also does not discuss using line array speaker sound reinforcement systems.
An amplification system, namely by sources, sound mixer, peripherals, power amplifier and speakers, school athletic field broadcast sound reinforcement system is no exception. In the system, the preceding sources, sound mixer, peripheral equipment, etc., can be matching (the more technical articles, you are free to access). This article is primarily on the amplifier and speaker selection, a theory of inference, then the speaker layout and matching discussions.
Because it is outside, its acoustic properties comply with the conditions of a free sound field and the law, it and venues, such as indoor acoustics are quite different. Accordingly, we are considering options for sound reinforcement sound field mostly consider two aspects, one is the sound field characteristics of the layout; the second is based on usage requirements and price/performance ratio, etc.
The following explains:
A sound field characteristics:
General track as lumbar circle, and is standard comparison site, surrounded by spacious and larger. Consider a uniform distribution of the acoustic field should be based on distributed speaker layout, single account General site is not doing speaker rack and pipeline embedded, not have distributed sound reinforcement of conditions, the use of the rostrum on the side of the centralized form of the more common sound reinforcement. This form is in place on both sides of the rostrum, the full-frequency sound box 4-8, speaker arrays, the various speakers separately adjust the radiation angle and does not do stereo sound reinforcement, to ensure that the entire track and field uniform distribution of the sound field.
Under the freedom of acoustic characteristics of sound field, regardless of the speaker repeat coverage be somewhere from the rostrum of the sound pressure level: LP = Ls + 10lgW + 10lg (Q/4 l r 2)
-Ls: speaker sound sensitivity W: drive power
R: the distance from the speaker: speaker volume n
Assuming that, select a fine speaker, its technical parameters are as follows, using the formula to calculate the distance of 100 metres at the rostrum of the sound pressure level: Q = 180 °/arcsin (sin45 ° * sin25 °) = 10.34 out Ls = 99dBW = 500Wn = 4
LP=99+10lg500+10lg(10.34/(4*3.14*1002))
=99+27-41=85dB
As the rostrum on both sides of the layout of a set of speaker arrays, and not as a stereo mode sound reinforcement, do not coincide and even covers the entire athletic field, the sound pressure level to meet the language and General music sound reinforcement.
Second, the speaker configuration
Speaker selection, it is first necessary to consider its radiation angle. General speaker of the specification will provide its horizontal and vertical radiation angle, such as 60 ° x 40 °, 90 ° x 60 °, where the first number represents the level of radiation angle, the second number represents the vertical radiation angle. According to the foregoing requirements, as the track field in the centralized sound reinforcement programme, you must use the small radiation angle of thespeaker, on the one hand, as far as possible reduce multiple speaker sound interference between, on the other hand, can make the sound radiation distance increases, the so-called remote speakers.
In actual use, the author recommended 60 ° x 40 ° or smaller radiation angle. Shall consult the speaker information, there are a number of tube amps, for example, the United States C brand speakers R series box.
In addition, the speaker set-up, to take full advantage of geometric acoustic mapping methods, on the speaker's voice and radiation angle for simulation, by adjusting, final speakers of hanging height, angle and so on.
Select the speaker has a metric is the input power. This indicator reflects the speaker units affordable electric power input driver. It is assumed that the conversion efficiency of certain circumstances, of course, the greater the power, radiation sound energy is also bigger, meet sound pressure value can be reduced by the number of speakers, which reduces multiple speaker stack of acoustic interference phenomena, to improve the sound quality is good.
Also, with regard to the determination of the sound pressure value. Meet to hear clearly the conditions, sound pressure value at 70-80dB, as system margin to 85dB meets most schools athletic field broadcast sound reinforcement requirements. There is no need to set a high standard, this can significantly reduce the system cost.
3. Select power amplifier
The power amplifier and speaker of the match, not necessarily to the conclusion that the author is not prepared to discuss in the article. Here only the amplifier and speaker of the connection mode. As we all know, the power amplifier and speaker of the connection mode stereo (Stero), monaural (mono) parallel and bridge (Bridge) method. As mentioned above, in order to meet the sound field in full uniform coverage, the system will work in mono mode, the same reason, the power amplifier and speaker also works in the latter two connection methods. As for the amplifier is working to bridge the output mode, it is first necessary to consider the reliability of the power amplifier, a second to consider load (speakers with an impedance of series-parallel) size. The general principle is that the amplifier's reliability, load impedance in 4-8 Ω, select the type of output mode, it can also reduce the cost of some power amplifier, the other may in his discretion select Mono parallel output mode.