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Frequency Response??

Discussion in 'Speakers' started by Jonny*D, May 22, 2005.

  1. Jonny*D

    Jonny*D Active Member

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    Can't someone please explain. What does 70Hz-20kHZ+- 3dB mean

    Would 60Hz-20kHZ+- 3dB be better?
     
  2. FeisalK

    FeisalK Well-Known Member

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    3dB is significant becasue it is the amount of volume/SPL that is noticeable. so, ±3dB at 70Hz means the bass starts noticeably getting softer at 70Hz.

    If you are not using a subwoofer 60Hz is better, in fact floorstanders go all the way down to 40Hz or lower before rolling off.

    If you have a sub, a higher rolloff might mean that it is easier to integrate the sub and mains. YMMV of course
     
  3. Dick Boneske

    Dick Boneske Well-Known Member

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    I believe the decibel scale was developed by Alexander Graham Bell. He picked 1 db as the minimum change in sound level that a human could detect. A +3 db change represents double the sound level.

    To illustrate this, if a sound is produced by a device at some level, and you add an identical sound source, the level change is 3 db. If you had four of these devices, the output would be 6 db louder.

    So, when a component is measured to be -3 db at some frequency, it is producing a change in sound level half of what it would be at 0 db. Humans can hear 20-20,000 Hz, so the closer to + and - 0 db a component is, the better.
     
  4. Mike^S

    Mike^S Well-Known Member

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    I think when you add another source with the same volume and location, the overall spl increases by 6dB. Increasing the volume of a single source by 3dB requires double the power.
     
  5. Wayne A. Pflughaupt

    Wayne A. Pflughaupt Well-Known Member

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    Jonny,

    Theoretically perfect response would be a flat line; for the sake of this situation let’s give the flat line a 0 dB reference. In the example you’ve given, it means response dips no more than 3 dB below the flat line, and rises no more than 3 dB above it, between 70 Hz-20 kHz. Make sense?

    Regards,
    Wayne A. Pflughaupt
     
  6. Chris Quinn

    Chris Quinn Well-Known Member

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    A 3dB increase does not double the loudness. It take doubling the power to achieve a 3dB increase in volume. Here is a link to a sound ramp that decrease at 6dB per tone and then at 3dB per tone.
     
  7. Jonny*D

    Jonny*D Active Member

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    Thanks everyone!
     

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