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The real world importance of cabinet bracing is?

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  • Originally posted by andy19191 View Post
    We want the layer that moves least to be on the outside to radiate sound and this is normally the constraining layer.
    Interesting.
    But unless we are operating outside the bounds of plate theory, this should not be possible.
    You may recall that classic plate theory states that during deformation normal to the plane of the three layers, the thickness of those layers cannot change. It is for exactly this reason that high shear strains are induced in the damping layer. Your inference that one of the three layers moves normal to the plane (radiates sound) less than the others implies the damping layer deforms axially where it is least effective.

    I think you knew this though, because you correctly pointed out earlier and noted that the KEF braces were placed strategically to counter resonant cabinet modes where cabinet deformation was greatest. One would be maximizing damping by placing the damping layers here due to maximum deflection.

    Originally posted by andy19191 View Post
    Yes but their damping material will be relatively stiff and not soft or else it wouldn't create the results shown.
    I might correct you to say "operating within the transition range between glassy and rubbery."

    I found another doctoral paper on CLD (attached) that discusses much of this and I think is very insightful and easy to follow.

    https://www.researchgate.net/publica...al_Application

    Others may note that in it, 50A silicone rubber is shown experimentally to have modest damping properties.... Porsches not Bugattis


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    • I found the EAR white papers easy to understand. https://earglobal.com/en/aircraft/

      The last two on the lower left

      Also there are some videos but I've not watched them.
      Last edited by jhollander; 01-11-2019, 12:25 AM. Reason: added content
      John H

      Synergy Horn, SLS-85, BMR-3L, Mini-TL, BR-2, Titan OB, B452, Udique, Vultus, Latus1, Seriatim, Aperivox,Pencil Tower

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      • Funny that Kef mentions the Ls3/5a in their design process, a monitor designed
        to "breath". The designers tried to take advantage of the cabinet resonance
        and tune it so it is complimentary. 1976-29 LS3:5.pdf
        Guess xmax's age.

        My guess: 15. His grammar is passable. His trolling is good.

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        • Originally posted by gregrueff View Post
          But unless we are operating outside the bounds of plate theory, this should not be possible.
          Plate theory involves some large assumptions that are reasonable for plates in order to make the sums easier. These assumptions don't hold over significant areas of a speaker cabinet and the boundary conditions for the areas where they do hold are going to be largely unknown in practise.

          The driver/s hammer on the structural layer putting work into it with no work being directly injected into the damping or constraining layers. The structural layer performs work on the damping layer (which needs to push back hard enough to transfer enough work to be worthwhile hence the stiff not soft business). Some work is dissipated in the damping layer and some work is done by it moving the constraining layer. This work is less than that injected into structural layer and so the constraining layer would be expected to move less than the structural layer (one or two caveats).

          Originally posted by gregrueff View Post
          I might correct you to say "operating within the transition range between glassy and rubbery."
          This is irrelevant to why the damping layer needs to be reasonably stiff and not soft for effective constrained layer damping. Repeating again what I said earlier is probably not useful and perhaps it may be wisest to accept I haven't got it across and let it drop until I have sorted the FEM damping models and can show some pictures.

          Originally posted by xmax
          Funny that Kef mentions the Ls3/5a in their design process, a monitor designed
          to "breath". The designers tried to take advantage of the cabinet resonance
          and tune it so it is complimentary.
          Not sure I understand. If you are referring to the beech vs pine battens this seems to have been to avoid having two resonances reinforcing at the same frequency (if anyone can access the Harwood AES paper we would know more). The KEF B110 driver has a modest pressed steel frame which resonates in the passband (recall seeing a plot of this on the web but cannot find it - anyone?) and, from the paper you linked to, it would seem that with pine battens the frequency of the "driver bouncing on the baffle" cabinet mode shown earlier and in the KEF paper coincided with it whereas with beech battens the frequencies were sufficiently different.

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