Speakers

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Speakers

• Read Yamaha manual pgs 209-221.
• The cone, usually made of paper, plastic or
  metal, is attached on the wide end to the
  suspension.
• The suspension, or surround, is a rim of flexible
  material that allows the cone to move, and is
  attached to the driver's metal frame, called the
  basket.
• The narrow end of the cone is connected to the
  voice coil.
• The coil is attached to the basket by the spider,
  a ring of flexible material. The spider holds the
  coil in position, but allows it to move freely
  back and forth.

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Speakers cont

• The voice coil is a coil of wire, usually wrapped
  around a piece of magnetic metal, such as iron.
• Running electrical current through the wire
  creates a magnetic field around the coil,
  magnetizing the metal it is wrapped around.
• The field acts just like the magnetic field
  around a permanent magnet It has a polar
  orientation -- a "north" end and and a "south"
  end -- and it is attracted to iron objects.
• With an electromagnet you can alter the
  orientation of the poles. If you reverse the flow
  of the current, the north and south ends of the
  electromagnet switch.

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Speakers cont

• Essentially, the amplifier is constantly
  switching the electrical signal, fluctuating
  between a positive charge and a negative charge
• The current going through the speaker moves one
  way and then reverses and flows the other way
  causing the voice coil to move in and out.

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Check this out

• Howstuffworks "How Speakers Work"

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Speakers cont

• When the coil moves, it pushes and pulls on the
  speaker cone. This vibrates the air in front of
  the speaker, creating sound waves.
• The electrical audio signal from the amplifier
  dictates the rate and distance that the voice
  coil moves.
• This, in turn, determines the frequency and
  amplitude of the sound waves produced by the
  diaphragm. That is how a speaker works.

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Speaker Impedance

• Speaker impedance is the load or resistance that
  the amplifier sees when it is driving the
  speaker.
• Speakers come built in various impedances.
  Usually 16, 8 or 4 ohms.
• Generally the lower the impedance the more
  efficient the speaker is.
• A speakers efficiency is measured in db/watt _at_ 1
  meter.
• Every time you hook up another speaker in
  parallel the impedance gets dropped by ½
• The lower the impedance the harder the amp has to
  work to drive the load of the speakers.

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Speaker Impedance

• Some amplifiers are rated to safely run at a 2
  ohm load. Generally try to avoid this as it makes
  the amplifiers work very hard to drive the
  speakers. Harder work more heat greater
  chance of failure. Try to keep your speakers set
  up to not make the amp drive a greater load than
  4 ohms.

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Speaker Power Ratings

• Continuous eg. 120 watts Refers to the level of
  long term average power that the loudspeaker will
  handle.
• It is usually measured using a sine wave or
  weighted noise input
• Program Power Handling eg. 240 watts
• Is measured using a test signal that approximates
  a real world program signal. Actual program
  signals have less long term heating effect for a
  given power level.

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Speaker Power Ratings

• Peak Power Handling eg. 480 watts
• Refers to the maximum instantaneous, short term
  power that loud speaker will handle, short term
  refers to intervals under a second, generally no
  more than 1/10th of a second.
• Manufacturers tend to rate their speakers for
  more power handling than they can actually handle
• You should underestimate the amount of PROGRAM
  power that a speaker is rated at and use that as
  the actual power that the speaker will handle in
  real life environments.

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Compression Drivers and Horns

• A compression driver is used to reproduce High
  Frequency sound.
• They come in different sizes measured by their
  throat diameter. 1, 1.5, and 2 are the most
  common sizes.
• These tiny speakers are attached to a horn to
  direct their energy at the audience in a
  controlled beam or pattern.
• Dispersion of a horn is the angle that it covers
  measured in degrees. Typical dispersion patterns
  for horns are 70-120 degrees horizontally and 60
  or 40 degrees vertically. The wider the
  dispersion pattern the shorter the throw or
  distance the driver can send high frequency
  waveforms.

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Speaker Enclosure Types

• SEALED ENCLOSURES
• In a sealed speaker setup, the driver diaphragm
  compresses air in the enclosure when it moves in
  and rarefies air when it moves out.
• These enclosures are less efficient than other
  designs because the amplifier has to boost the
  electrical signal to overcome the force of air
  pressure. The force serves a valuable function,
  however -- it acts like a spring to keep the
  driver in the right position. This makes for
  tighter, more precise sound reproduction.

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Speaker Enclosure Types

• BASS_REFLEX
• Other enclosure designs redirect the inward
  pressure outward, using it to supplement the
  forward sound wave. The most common way to do
  this is to build a small port into the speaker.
  In these bass reflex speakers, the backward
  motion of the diaphragm pushes sound waves out of
  the port, boosting the overall sound level. The
  main advantage of bass reflex enclosures is
  efficiency. The power moving the driver is used
  to emit two sound waves rather than one. The
  disadvantage is that there is no air pressure
  difference to spring the driver back into place,
  so the sound production is not as precise.
• More efficient, boomier sound, not as precise
  sound quality compared to sealed enclosure

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Speaker Enclosure Types

• A passive radiator speaker uses a second
  "passive" driver, or drone, to produce similar
  low frequency extension or efficiency increase or
  enclosure size reduction as do ported enclosures.
  In theory, such enclosures are variations of the
  bass reflex type, but with the advantage of
  avoiding a relatively small port or tube through
  which air moves, sometimes noisily. As well,
  tuning adjustments for a passive radiator are
  usually much easier. And with the disadvantage
  that a passive radiator requires precision
  construction quite like driver design, thus
  increasing costs

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Line Arrays

• A line array is a group of radiating elements
  arrayed in a straight line, closely spaced and
  operating with equal amplitude and in phase
• line arrays are useful in applications where
  sound must be projected over long distances. This
  is because line arrays afford very directional
  vertical coverage and thus project sound very
  effectively.

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