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دایره المعارف تاسیسات برق (اطلاعات عمومی برق)

CEILING SPEAKERS

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When sound is needed in rooms that have low ceilings such as many classrooms, fellowship halls, and lobbies, ceiling speakers are often the best choice to deliver even sound coverage.

Sound spreads as it travels away from its source, and as it spreads it also reduces in level. This is known as the “Inverse Square Law” which states that each time the distance from the source doubles, the level is reduced 6 dB. In rooms with high ceilings it is often possible to cover the room evenly with sound using just a single loudspeaker (see image 1).

By aiming the loudspeaker at the furthest listener and selecting a loudspeaker with the correct coverage to match the room and the mounting height it is possible to get even coverage. However, if the ceiling height is low even using a very directional loudspeaker it might not be possible to achieve even coverage.

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In such cases the preferred solution is often the use of ceiling mounted loudspeakers facing straight down.

Within limits the use of ceiling speakers with wider coverage angles is preferred since it allows you to cover the space with fewer loudspeakers (see image 2). However, extremely wide coverage angle speakers (say over 90 degrees) do not provide as much advantage as you might think since the inverse square law still applies and listeners more distant from the loudspeaker will still get less level even though they are within the coverage angle of the speaker.

Layout of the speakers is usually done in a hex or square pattern.

The hex pattern will provide the most even coverage for a given number of loudspeakers, but is not always practical because of ceiling tile grids, lighting fixtures, HVAC registers, and other objects on the ceiling. An edge to edge layout will provide the least even coverage because of the gaps between the coverage of the speakers. A minimum overlap layout is better, and for the most even coverage the center to center coverage is ideal(see Image 3).

PictureProviding even coverage in a room with a low ceiling can require a large number of loudspeakers, but fortunately there are relatively inexpensive ceiling loudspeaker choices available (please refer to the SoundPress section in this newsletter for more information).

When ceiling loudspeakers are installed in a drop ceiling, the weight of the loudspeaker should never be resting on the tiles as they will bend and sag. Instead the weight should be distributed onto the ceiling support grid using a tile bridge. A safety support line to building structure overhead is always suggested and may be required by building codes.

Wiring to the ceiling speakers is typically done using a so called “constant voltage” distribution system. The most common of these systems are the 70 volt or 25 volt systems. The voltage specified is the level the amplifier puts out at maximum output. Each loudspeaker has an associated transformer that connects the speaker to the line from the amplifier, and allows the relative level of each speaker to be selected by the installer.


Most churches have at least some locations where ceiling loudspeakers are the preferred choice. Now you have some background to understand where such speakers are best used, and how they should be applied.

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