JBL Sub Air Flow problem

Discussion in 'Speakers & Subwoofers' started by ClaytonMG, Oct 20, 2003.

  1. ClaytonMG

    ClaytonMG Stunt Coordinator

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    My sub has air flow problems. It's apart of this JBL speaker package. It's 100 watts and an 8" woofer. It sounds like there's too much air coming out of it. I thought it might be bottoming out, but that would mean it was bottoming out whenever there was a little bit of bass. Any suggestions?
     
  2. MichaelDDD

    MichaelDDD Supporting Actor

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    What do you mean by "too much air coming out of it?"

    A subwoofer HAS to move air to make bass. How much bass a speaker puts out is simply a function of it's suspension travel and how much power you feed it. [​IMG]

    Do you hear "chuffing" sounds? That's called "port noise" and is the sound the air makes as it passes over the sharp edge of the port's exit.

    Also, were you playing really low test tones or watching a movie w/the sub cranked way up? Possibly, you were playing the sub at frequencies below the tuning frequency of the cabinet.

    The port(s) in a ported enclosure tune the sub to a specific frequency, i.e. 30Hz. If you try to play the sub below it's tuning frequency, it becomes "uncoupled" from the enclosure and just starts flapping around as if it's not in an enclosure at all. You can blow the sub that way.

    So, please elaborate so we can help.
     
  3. ClaytonMG

    ClaytonMG Stunt Coordinator

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    Well I know air has to come out. [​IMG] It's chuffing sounds. The sub goes as low as 20hz (same as my reciever). It happens when watching movies and using the crossover tests. So I am guessing it's "port noise." How do I fix it?
     
  4. MichaelDDD

    MichaelDDD Supporting Actor

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    Hi Clayton,

    Well, honestly, you can't really expect an 8" sub to go down to 20Hz....30Hz is probably more realistic. [​IMG]

    There is no "fix" for port noise. The only thing you can do is not play the sub below it's tuning frequency.

    Is there a subsonic filter on that sub? Usually, it's selectable/defeatable. If it has one, turn it on. The designer of the amp/sub will typically set the frequencies on the subsonic filter to coincide with the tuning of the cabinet to ensure the sub isn't played below is tuning frequency, thus preventing damage.
     
  5. ClaytonMG

    ClaytonMG Stunt Coordinator

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    I don't think my sub has a subsonic filter. And the sub does it even when the bass isn't that low. It's mostly when something is pounding.

    Clayton
     
  6. Justin_T

    Justin_T Stunt Coordinator

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    Honestly, I recommend getting a new sub. Something your system won't be able to push fully. Depending on your price range you could go with a powerhouse Pioneer downfiring sub or a dual Yamaha. If you've really got cashflow coming in, check out the Sunfire subs. Beautiful sounding bass!
     

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