Course LV-1: Speakers

Speaker Components : fig (1)
Most of the Speakers consists of a lightweight diaphragm, or cone, connected to a rigid basket, or frame, via a flexible suspension that constrains a coil of fine tinsel wire to move axially through a cylindrical magnetic gap.


fig (1)

Speaker Method of Operation :

When an electrical signal is applied to the voice coil, a magnetic field is created by the electric current in the voice coil, making it a variable electromagnet. The coil and the driver's magnetic system interact, generating a mechanical force that causes the coil (and thus, the attached cone) to move back and forth, thereby reproducing sound under the control of the applied electrical signal coming from the amplifier.


Speaker Types:

the speakers generally can be classified to different categories from different point of views like type, usage , installation ,.... but the important classification is the one according to sound propagation which determine the possibility to use the speaker in a a certain place or not .

the speakers will be classified according to sound propagation to the following:
  1. Unidirectional speakers.
  2. Omnidirectional speakers.


1- Unidirectional speakers: fig (2)

Uni-directional speakers only send sound in one direction - forward. This is normal for most PA speakers

Unidirectional speaker's types are:
  • round reflex horn loudspeaker.
  • Square reflex horn loudspeaker.
  • Cylindrical dynamic loudspeaker.
  • Spherical dynamic loudspeaker.
  • wall mount loudspeaker.
  • Ceiling mount loudspeaker.


fig (2)

2-Omnidirectional speakers: fig (3)

Omni-directional speakers usually send sound in all directions, front and back. They are not standard, and are usually found in outdoor.


Omnidirectional speaker's types are:
  • two-ways box speakers.
  • three-ways box speakers.
  • four-ways box speakers
  • Sound column.


fig (3) 


Speaker specifications:


speaker specifications generally include basically:

  • Speaker type
  • Size
  • Rated power maximum: input power before destroying the loudspeaker; it is never the sound output the loudspeaker produces.
  • Impedance :typically 4 Ω (ohms), 8 Ω, etc.
  • Baffle or enclosure type.
  • Number of drivers : two-way, three-way, etc.


and optionally:

  • Crossover frequency: for multi-driver systems only– The nominal frequency boundaries of the division between drivers. 
  • Frequency response.
  • Sensitivity.
  • Maximum SPL : The highest output the loudspeaker can manage.


SPEAKER ENCLOSURES

Speaker enclosures, usually referred to as baffles, are designed for two types of mounting:
  1. flush.
  2. surface.


1- Flush-mount:

Baffles are typically used in new construction projects or in applications where the ceiling is removable acoustic tile. Both of these applications permit the back box to extend behind the ceiling surface and the speaker grill to be flush-mounted.

2- Surface-mount:

 Baffles are used in existing buildings where it would be extremely costly to channel and resurface the walls to accept concealed conduit and back boxes. Although surface-mount baffles are designed to look as attractive as economically possible, flush-mount baffles are recommended to avoid the highly visible enclosure and wiring.


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