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Thread: Adding Bracing

  1. #1
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    Adding Bracing

    When adding more internal cabinet bracing, do you usually get back the lost internal volume by adding to the overall cabinet depth and inch or so (math to be determined)? Does it matter what dimension increases typically> Seems like adding on to the back would be the easiest for sure.

  2. #2
    Senior Member RMC's Avatar
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    Hi Drugolf,

    Ideally you should make up for it on the whole cabinet dimensions in order to keep your box proportions right. On a large box braced with 2X3" for example I doubt adding just an inch or so to depth would do the trick. You need to calculate all bracing volume and add that total number to box volume. Regards,

    Richard

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    Administrator Mr. Widget's Avatar
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    I think you'll be fine just adding to the depth. Most vintage JBLs were too shallow in my opinion and will only get better if they are a bit deeper. That said, as suggested by RMC, proportions do matter. You want the various dimensions to be odd multiples of each other. 1:1, 2:1, etc. ratios are not good as you'll likely get standing waves within the cabinet which will be audible.


    Widget

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    I think that Drugolf might be adding bracing to an existing cabinet ( perhaps those that house his twin Altec 414z's ).

    If that's the case he would first run some WinISD sims of before & after ( the bracing is added and the box volume shrinks a bit ).

    The overall effect to the box/driver alignment might not be anything to worry about ( especially when an extra batt or two of insulation can recover some of the lost Vb in the way of adding virtual volume ).


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    EarlK is correct. In this particular case we are building Altec model 19's and after reading various threads it sounds like adding a little more bracing might be a good thing so it won't be a radical increase in mass internally. Overall, yes I could see the need to add to all dimensions.

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    Quote Originally Posted by Drugolf View Post
    EarlK is correct. In this particular case we are building Altec model 19's and after reading various threads it sounds like adding a little more bracing might be a good thing so it won't be a radical increase in mass internally. Overall, yes I could see the need to add to all dimensions.
    The most important thing is to cross-connect panels. Many people try to add bracing by adding braces that only really add thickness- rib type "bracing". You want opposing panels (left and right sides, top and bottom, front and back) to have rigid connections to each other in the middle of the panels- so that the most flexible points are not able to "balloon" (the lowest frequency issues are solved by adding rigidity). Damped bracing is a whole 'nother ball of wax, worth looking into but takes some care. A few well-thought out braces shouldn't affect cab volume that much, but if you're going to do a serious bracing scheme, you'll want to add a little cabinet volume to accommodate.

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