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Thread: 2214h and impedance response for vent length thuning

  1. #16
    Senior Member davidpou's Avatar
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    Quote Originally Posted by RMC View Post

    Bonjour Davidpou, and other members who replied here.

    You seem to be giving yourself a lot of trouble to confirm the calculated box tuning frequency (Fb). The method I use is probably the simpler one and requires no instruments nor a microphone as suggested by Widget.
    Thank you so much ! Indeed I felt like lost in the middle of the sea with just a tiny buoy thrown by Mr Widget...

    An other great advantage of this method is that one doesn't have to take the woofer off the box many times in order to tune the vent length: in my case provided it was radius I coudn't use paperboard or something to push forward or backward for thesting: I had to take off the 2214H and this is risky even done carrefully.... So yes excellent !
    Last edited by davidpou; 04-25-2017 at 02:57 AM. Reason: add something

  2. #17
    Senior Member davidpou's Avatar
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    Quote Originally Posted by Lee in Montreal View Post
    Room EQ Wizard is free and allows to sweep all day long with 0,1Hz increments. Plus dozens of other very useful functions. ;-)
    Thanks Lee I do use Rew for the measurements you see.
    Just did not want to make the small circuit they suggest to measure TS parameters: not shure to do i right , afraid to blow my drivers, coudn't be bothered....
    so I bought the Dayton thingy...

  3. #18
    Senior Member RMC's Avatar
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    Hi Davidpou,

    You're right about handling (install and remove) of large or heavy drivers is a risky business even when done carefully. Many years ago in removing a large and heavy driver (not my 2214H) the Philips screwdriver accidentally slipped off my hand... and went right through the surround

    It cost me a genuine recone job $$ so now I proceed differently and ALWAYS put the screwdriver away before even thinking about touching the driver...

    Richard

  4. #19
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    Quote Originally Posted by edgewound View Post
    An easier way is to download a free app to your smartphone called "Signal Gen". It does sweep tones from 20-20KHz in 0.1 increments while displaying the exact frequency.

    It's a great gizmo for such applications, as well as finding the resonant frequency of hanging pictures and other breakables.
    Yes. And, even better, do the freq vs voltage (impedance) plot - need a good voltmeter. However, truth be said, I doubt anyone could hear +/- 10% difference. It is a very broad null point. The technique for this is on site in the JBL Enclosure Information Manual.

  5. #20
    Senior Member jerv's Avatar
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    Quote Originally Posted by Earl K View Post
    Jervs impedance plots were created within his knock-off 4425 boxes and those might not have been ported ( his graphs stop at 20 hz so it's very hard to know from the graphs if he made a sealed or ported box ).

    That picture does show a very gentle rise starting at 35hz going down to 20hz ( meaning, there might actually be two peaks present ) .
    Hi.

    This is a long time ago - but this is definitely my measurement. And as Earl says: in my knock-off boxes, which is ported and at about 54 litres internal volume.
    And indeed there are two peaks present - you cannot see the other one - as I remember: it is quite damped, and is down at 16-18 Hz.

    Reflex tuning is at the impedance minimum between the two peaks: in this case about 35 Hz.

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