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Homework Help: Sub woofers and tweeters wavelength

  1. Sep 27, 2010 #1
    1. question



    2.hello Dear ,

    I have a question for you please ,
    When you buy a home cinema system, you can place the subwoofer almost anywhere, even behind your couch.
    But the tweeters (speaker for high frequencies) must be placed very accurately. Explain why!
    Hint: use wavelengths for explanation (yes, with numbers). Give a strong argument.It is all about the size of wavelengthes. Think again back to the camera obscura.





    3. The attempt at a solution
    my answer is :

    speed of sound at sea level Cs = 340.29 m / s
    is a constant

    Cs = λ / T

    Cs = λ (wavelength) . v (frequency)

    With high frequencies like tweeters , we will get lower λ (wavelength)

    For example of Frequency of 150 HZ sound wave (for sub woofers 20-200 Hz) .
    The λ (wavelength) = 340.29 / 150= 2.2686 m

    With 5000 Hz (tweeters have frequency between 2000-20000 Hz)

    The λ (wavelength) = 340.29 / 10000 = 0.034029 m =3.4029 cm

    The long wavelength sounds (lower frequencies) of the Subwoofer will diffract around the corners of the room more efficiently than the more directional, short wavelength sounds of the tweeters. So that we can put the subwoofer anywhere but the tweeters are directional . Since the bass frequencies have longer wavelengths, they will spread out more than the high frequencies. The high frequency sound spreads out less than the low frequency sound.

    And for the Bass of Subwoofer it is called low-frequency, high-amplitude sound waves. So
    lower-frequency = higher- λ (wavelength)

    Higher λ (wavelength) = Higher T(Time duration needed)

    Co (speed) = distance / Time

    So ..
    Higher T = higher distance

    So , subwoofer can be put anywhere as its sound is omni-directional. The very long wavelength of the very low frequency bass sounds reproduced by the subwoofer usually makes it impossible for the listener to localize the source of these sounds . Because of long wavelength there is little difference between the information reaching a listener's left and right ears, and so they cannot be readily localized , so location does not matter .

    But tweeters with high-frequencies have lower wavelength .

    Lower-wavelength need lower time to move the distance

    So lower time = lower distance

    Than tweeters can be readly localized with short wavelengths and no difference between information reached to ears.
    So we should put the tweeters accurately in place inline with ear level so all the room will be of wavelengths !

    IS IT RIGHT ? :)
     
  2. jcsd
  3. Sep 27, 2010 #2
    a correction .. or addition :

    The long wavelength sounds (lower frequencies) of the Subwoofer will diffract around the corners of the room more efficiently than the more directional, short wavelength sounds of the tweeters. So that we can put the subwoofer anywhere but the tweeters are directional . Since the bass frequencies have longer wavelengths, they will spread out more than the high frequencies because wavelength are long enough to bend around posts and corners. The high frequency sound spreads out less than the low frequency sound because short wavelength are not able to bend around corners and posts so they are more directional.
     
  4. Oct 6, 2010 #3
    Anybody is here ?>???
     
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