What happens when woofers/drivers "pop" or "fart?"

Discussion in 'Archived Threads 2001-2004' started by Haris Ellahi, Jan 23, 2003.

  1. Haris Ellahi

    Haris Ellahi Second Unit

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    When woofers/drivers of main speakers (not subwoofers) "pop" or "fart," what does that mean?
     
  2. Edward J M

    Edward J M Cinematographer

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    You are overdriving them and they are showing audible signs of distress. Permanent damage is imminent at this point.
     
  3. Vince Maskeeper

    Vince Maskeeper Producer

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    Any magnet driven cone has a maximum throw (excursion)-- the max distance the woofer can be pusted outward. When it hits this point, it will often make an unpleasent noise (because it is trying to vibrate a full cycle to complete a wave- and insead it hits its max and clacks).

    So, it just means the full travel of the driver has been exploited, and you are overdriving it.

    -Vince
     
  4. Patrick Sun

    Patrick Sun Moderator
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    Maybe it had a big bowl of chili for dinner... [​IMG]
     
  5. Aaron Garman

    Aaron Garman Second Unit

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    Nice thread "fart" Patrick! [​IMG]

    Aaron James Garman
     
  6. Chu Gai

    Chu Gai Lead Actor

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    Treating your connections with "Beano" may prevent that though [​IMG]
     
  7. Brett DiMichele

    Brett DiMichele Producer

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    When my Woofer (A Female Doberman Pinsher) Farts we usually
    vacate the room! (Quickly!)

    If a Driver Bottoms out (the motor structure pulls the
    driver down past it's mechanical suspension travel) it will
    make a loud *CLACK* sound as the Voice Coil Former
    physicaly touches the T-Yoke (Magnet Backing Plate). This
    can cause the Voice Coil Former to bend or warp from the
    blunt force (The Former is usually Kapton or some sort of
    Pressed Paper Material) If the Voice Coil Former is bent
    then the voice coils will also be bent which can cause them
    to drag inside the Magnetic Gap and will ultimately lead to
    a short circuit as the Voice Coil repeatedly rubs against
    the Magnet and rubs the Shelacking off of the Voice Coil
    Wire and ultimately shorts out.

    When the driver is overextended the opposite way (outwards)
    the Surround will often make a very loud *POP* sound
    as it is traveling further than it was designed to do. Over
    Extending the driver this was is slightly "safer" because
    the surround usually won't let the driver go any further.
    But if the surround is not strong enough to stop the force
    of the moving cone it can cause the surround to tear, or
    seperate from the cone (it would most likely tear first as
    the glue they use to bond a surround to a cone is fairly
    strong stuff). And if the Motor Structure is strong enough
    it is also possible to dislocate the whole Voice Coil/Former
    assembly from the underside of the cone.

    Either way, Pushing a driver past it's linear suspension
    travel is BAD and if you hear that sound then it's time to
    quickly turn the volume down and figure out why it is that
    you care causing this to happen.
     
  8. Haris Ellahi

    Haris Ellahi Second Unit

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    Lets say that this is due to amplifier clipping. Will this cause more damage to the speaker or the amplifier?
     
  9. Brett DiMichele

    Brett DiMichele Producer

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    When an Amplifier clips it sends out square waves (imagine
    an ocean wave.. Nice and rounded crests.. Now lop off the
    top and you have a rounded slope with a flat top) Square
    waves will fry tweeters instantly if they do not have
    protection circuits (and still even with protection it could
    still fry it..)

    Clipping the Amp it's self can ultimately lead to failure
    from just driving them amp too hard but it doesn't happen
    as "instantly" as speaker damage will.

    If you are getting Popping sounds from a Mid Range or a
    Sub Woofer and the cone is moving a good deal, chances are
    you have too much power, rather than not enough.. When you
    tend to clip and amp is when the speaker can barely be driven
    with the amplifier at full gain (the speaker is hardly moving)
    but it's being sent a clipped signal because the amp is
    trying to work too hard.. The speaker tries to reproduce
    the square waves and will ultimately fail from heat damage
    to the voice coil..
     
  10. Haris Ellahi

    Haris Ellahi Second Unit

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    Thanks.

    For how long would I have to keep "playing" the speaker like that to damage the woofers/drivers?
     
  11. Chu Gai

    Chu Gai Lead Actor

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  12. Brett DiMichele

    Brett DiMichele Producer

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    Chu,

    Very GOOD read!

    The problem is as the article states, today even the cheapest
    of amplification units are far better dynamicaly then they
    were 10 20 years ago. Clipping is not easily heard by a
    novice or a pro when you have amps capeable of wide dynamic
    ranges from practicaly zero cycles clean up to 100 thousand
    cycles.

    I stick by the rule that too much power is never bad but
    not enough power is a very bad thing. It's better to have
    way more head room than you will ever need, and run the gains
    low.. Then to have too little power, run gain full and cause
    the amp to be overdriven and start sending out clipped
    signals...

    Some tweeters are a little more "stable" with square waves
    than others, Ribbons can handle somewhat square waves but
    Dome's can't do it they just give up the ghost in no time.

    When the day comes that a speaker can faithfully reproduce
    a Square Wave, that is the day that all of this clipping
    talk becomes a thing of the past.
     
  13. Chu Gai

    Chu Gai Lead Actor

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    never hurts to have more power...ask California [​IMG]
     

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