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    Senior Member davidpou's Avatar
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    Box tuning question

    Hi,
    I am still exploring box tuning with some 2214H.
    The first box of 52 liters has been built with the JBL TS parameters, and calculated with a french software. The Vb has been decided by the soft, which prescribe aswell a port length of an astoninshing 51 cm long (for 8.5 cm in diameter). In fact the Fb with this port in this volume gave a measured Fb at 20 Hz ! below Fs!, and only with a 36 cm long port I could measure the predicted Fb at 29.5 Hz…..
    So I started to doubt the french soft, and thanks to precious advice and with the help of this soft http://www.mh-audio.nl/reflexboxcalculator.asp I decide to buit a new box in the 70-75 liters range. I also thought that may be there was some issues with the woofer being 30 years old. So I measured its TS parameters. Over 8 caculated parameters, only 3 were at +/- 20 %, the others were in the 10 % range as compared to stock values from JBL. These are: Q(ms), Le and M(ms). I refoamed one of the woofer with mister Rick Cobb foam, but the tree parameters stayed almost unchanged.
    Anyhow my new boxes calculated with the new soft were done with the mesured TS parameters. Here is a picture of the results. In fact in order to obtain a 33 Hz Fb, I had to divide the port length by 2 !
    Here is my question : the second pic shows in red the 75 liters box with a 10 cm port length (diameter: 9.5cm) and the green curve is the 52 liters box with a 25 cm port length (diameter 8.5 cm). The response curve are almost the same and I could make the almost identical by a little port length tuning….
    What is the advantage of a bigger box ? (apart from inserting other drivers in the same box ?) ? how can one say that this woofer is “happier” in this volume rather than another ?

    Name:  CALCULS ENCEINTE TEST.jpg
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    Name:  BOXES COMPARISON.jpg
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    Last edited by davidpou; 06-04-2017 at 11:26 PM. Reason: presentation orthographe

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