General Principles of DJ Sound Amplification in Concert Halls

I’m a wedding DJ in Western Mass and the following are some thoughts on principles of sound amplification. Enjoy!

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“Setting of small and medium-sized rooms”

Wedding DJ amplification systems must be designed to deliver clean, clear sound in the right dynamic and frequency range with sufficient volume to all Audience seats, listening to music and speech programs probably more comfortable, create a sense of presence.

According to their function room, which set PA system, differ from each other. For example, in discos focus on the dance floor. The most important thing to create a uniform sound field over the heads of the dancers play the entire dynamic and frequency range of musical programs, and restrictions on the power used in sound reinforcement systems are almost nonexistent.
In the restaurants and night clubs PA system must have some flexibility. They have to translate to the same as the background, chamber, symphonic, blues, rock, disco and other music, as well as “live” musical performances. The same flexibility should have PA system and in concert halls.

Each room, depending on the architectural features and functionality requires an individual approach to the design of sound reinforcement systems. In this paper we propose to consider the characteristics of building sound reinforcement systems, based on the size of the hall, and not on functionality, suggesting that the premises can be used as multi-purpose.

With increasing space problems, clear (legible) sound and the level of the sound pressure, and hence the volume of playback of music and speech programs are growing. This is due to the fact that the further away from the sound source (speaker loudspeaker system) is a listener, the lower the volume level playing program. In space, where there is no reverb, such as on the street, the sound pressure level is reduced by half (6 dB) with distance from the source to the double distance.

The second problem that arises in this reverb playback applications specific to each room. If the listener is located near the speaker, it is in “direct field”. This field is where the sound is coming from the speaker louder reflected sound. At a distance from the speaker sound reflected from the floor, ceiling and walls of the room, louder sound coming directly from her.

This is where the problems begin.
In reverberant space is always a point where the reflected sound is stronger than a straight line. To be sure, the sound pressure level tends to a constant value in reverberant (diffuse) field, no matter where the listener. The distance from the speaker system on which the level of direct and reflected sound are called “critical distance.” When the listener is in a reverberation field, the sound he hears, Japan is largely a reflection from the floor, ceiling and walls of the room and only a small portion of it goes directly from the speaker. All these reflections reach the listener’s ear in a slightly different time periods, with a few more sound pressure than the direct sound. As a result, the listener is in the field of reverb, lost intelligibility and clarity of sound.

Reverberant field problem can be solved in two ways.
First – this is to change the shape and decoration reflecting elements of the walls and ceiling of the room. But in practice, change the interior of the premises in this way is almost impossible.
The second way – it is right to design complex sound reinforcement for him to overcome the reverberation field in a room.

The main focus in the design of sound reinforcement system, designed to work in a particular area should be given the choice of speakers. Speakers with a narrow radiation pattern sometimes referred to “ranged” (not standardized technical terms and jargon). The terms “long-range combat,” “melee” characterize how far the speakers can deliver clean, clear sound. It depends on the variance. To describe the principle of such systems can take an example from everyday life. Imagine a normal hose for watering. The water in the hose is suitable for top on its end with a constant pressure, and nozzle itself determines how water flows. If the nozzle is wide, the water will not pour, but if you change the nozzle on a narrower or hold the hose, the water will pour much further.

The same thing happens with sound. For example, if the midrange driver to connect with a wide mouthpiece, the system will “near or mid fight.” If its connected to the mouthpiece of a narrow-angle, you get a system of “ranged”. Using horn system with a narrow radiation pattern can solve the problem of room reverberation medium and large sizes. By increasing the sound pressure level of the direct sound are making that material music and speech programs became more clear and legible. System “ranged” are used not only to increase the sound pressure level, but also to focus on the sound of distant sound Audience field, with the sound pressure level of the direct sound will be reflected above. And this is the problem reverberation fields.

Consider the specific sound different size rooms and describe the public address system, which could be used in them.

Conditionally divided premises considered, depending on their size into three types – small with a volume of 300 m3, with average volume of 900 m3 and a large volume of 2700 m3. It should be noted that with such a difference in the size of the premises power sound reinforcement needed to maintain a certain sound pressure level (SPL) in reverberant field will be significantly different.
Consider a simple example, where we assume for convenience that the same sound system will work in a room with a capacity of 300 and 3000 m3. If the sound reinforcement system with a capacity of 100 W can provide in a small room average sound pressure level of 100 dB, the need for a large area is 10 times more power (about 1000 watts) to produce the same sound pressure level of 100 dB.
As desired acoustic power system is highly dependent on what music and speech programs, and how loud to articulate in a particular area. In Fig. 1 shows the average sound pressure levels in some typical cases.
Sound pressure level at a normal conversation at a distance of 30 cm is about 70 dB. For most people, the level of 120 dB causes pain. Sometimes live rock band sound pressure level reaches 115-120 dB and above. In what follows we assume that a given parameter in the halls of a sound pressure in the Audience seats, and the calculation shall be necessary to ensure that the sound pressure sound power emitters. The electric power is determined with the efficiency and sensitivity of the speakers.


~ by onefortheshow on September 23, 2012.

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