P. 1

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Loudspeakers ???

• Transducers??? that convert electrical signals
  into sound waves
• The current flow in
• the coil causes the diaphragm to move, thus
  causing changes in sound pressure

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Loudspeakers ??

• Loudspeakers usually consist of multiple speakers
  (drivers) to cover the full frequency range

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Woofer ?????

• Produces Low Frequen-cies

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Woofer Frequency Response
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Tweeter ?????

• Produces high frequencies
• Uses only one suspension medium.

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Tweeter Frequency Response
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Crossover ????

• Divides and routes the appropriate portions of
  the signal to each of the speakers in the system

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Crossover High-Pass
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Crossover Low-Pass
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Crossover Band-Pass
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Passive Crossover

• A passive filter is placed after the amplifier
• It cannot raise the gain on the signal

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Active Filter

• In active filtering the signal splitting occurs
  before it is amplified

• An active filter is so called because it requires
  electric power for its operation and can raise
  the gain of the signal
• enables adjustment of the frequency ranges

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Passive Speakers

• These do not contain an in-built amplifier and so
  must be powered by an external amp
• Used in most home Hi-Fi systems
• Do not require power leads
• May require fairly thick cables to carry the
  signal

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Active Speakers

• Have a built in amplifier and so can be used with
  small output signals
• Most PC speakers are active to boost the weak
  output (4W) from most sound cards
• Require only thin signal cables
• Increased weight
• Overall performance my be restricted by a poor
  amplifier

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Enclosures ??

• The loudspeaker enclosure serves as a passive
  processor of the sound, collecting and directing
  it to the desired location
• Without a baffle or enclosure low frequency sound
  from the front and back of the speaker will
  cancel each other out

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Infinite Baffle

• By completely enclosing the back of the speaker
  we get an infinite degree of blocking
• Stops low frequency cancellation
• Wastes energy produced by rear of speaker

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Vented Enclosure (Bass-reflex)

• The rear wave from the loudspeaker is delayed so
  that it emerges from the port in phase with the
  wave motion from the front
• Relies on strict relationship
• Enclosure size
• Size of opening (port)
• Resonance?? of loudspeaker

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QUESTION AND ANSWER
End