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Understanding the behavior of a conical cabinet.

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  • Steve Lee
    commented on 's reply
    I'm trying to figure out just how thick the cone material needs to be. If it is rigid and stuffed with fiberfill I suspect it doesn't need to be thick - just stiff/rigid?

  • Steve Lee
    replied


    Possible source -->


    https://www.workoutz.com/agility-cones.html

    Height Weight Base Dimensions Bottom Hole Dia.
    4 in 1 oz 3.5 x 3.5 in 2.4 in
    6 in 2 oz 5.25 x 5.25 in 5 in
    9 in 3 oz 5.75 x 5.75 in 4.7 in
    12 in 6 oz 7 x 7 in 6 in
    15 in 10 oz 8.75 x 8.75 in 6.5 in
    18 in 1 lb 2 oz 9.5 x 9.5 in 6 in
    *Approximate dimensions


    Leave a comment:


  • LIDAR
    commented on 's reply
    You're on to something there Dukk. However you might not want all that weight, so maybe a much thinner spacer and some pourable epoxy.

  • Dukk
    replied
    Originally posted by Steve Lee View Post
    Would these be suitable for a mid driver in a traditional box enclosure?

    https://www.amazon.com/REEHUT-Plasti...152606&sr=8-13
    Cover that cone in a couple of layers of fibreglass and you may have something. Or do the layup internally and remove the cone after to reveal a smooth paintable surface if it is going to be exposed.

    Stack one cone inside another with something like a 3/4" spacer at the flanges, fill the resultant gap between them with a mortar mix and you have something very intriguing..

    Leave a comment:


  • Steve Lee
    replied
    Good perspective.

    I'll look into stiffer cones in my future searches - I just know that there is something suitable out there with far less cabinet cabinet volume robbing mass than making pyramids from wood.

    Leave a comment:


  • zx82net
    replied
    Originally posted by Steve Lee View Post
    Would these be suitable for a mid driver in a traditional box enclosure?

    https://www.amazon.com/REEHUT-Plasti...152606&sr=8-13
    In my experience, those kind of cones, are made of something very tough, but with low rigidity, like low-density polyethylene, or polypropylene. I think there is a chance they could transmit significant pressure from the woofer. It you are looking for pre-made enclosures, you might be better looking for something in ABS, polycarbonate, or melamine. Perhaps some kitchenware. Melamine it really pretty stiff but has quite a dead sound to it, a bit like wood, might be worth looking into.

    Leave a comment:


  • Steve Lee
    replied
    Would these be suitable for a mid driver in a traditional box enclosure?

    https://www.amazon.com/REEHUT-Plasti...152606&sr=8-13

    Leave a comment:


  • billfitzmaurice
    replied
    Originally posted by zx82net View Post
    So in conclusion: Cone length does not need to be tuned to driver parameters. Instead, for a given volume of cone, it is probably best to determine the diameter-to-length aspect ratio based on baffle constraints. Sound reasonable?
    Yep. You'd chose a baffle dimension and the cone length would be whatever was required for the desired box volume. The difference between a rounded cone or a segmented cone would be minimal other than rounded be the most resistant to vibration.

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  • zx82net
    replied
    Originally posted by LOUT View Post
    The modelled BaffleStep effect from a flat/circular face looks very similar to a square baffle with edge-to-edge dimensions the same as the circle's diameter....so I'm not sure the flat circular shape is worth the trouble compared to a square-base pyramid on its side.

    If you're thinking about a circular front (like a full radius roundover), then it smooths out the ~2db bump that comes after/above the BaffleStep, but that's about it, so likewise probably not worth the trouble if you're mostly interesting in BSC if you can deal with it in the XO instead....Unless you're doing it for asthetic purpose.
    I'll be printing it or printing and casting it, so the circular and spherical shapes come at no cost. In fact, they are probably cheaper since they'll be more material efficient!

    Leave a comment:


  • LOUT
    replied
    The modelled BaffleStep effect from a flat/circular face looks very similar to a square baffle with edge-to-edge dimensions the same as the circle's diameter....so I'm not sure the flat circular shape is worth the trouble compared to a square-base pyramid on its side.

    If you're thinking about a circular front (like a full radius roundover), then it smooths out the ~2db bump that comes after/above the BaffleStep, but that's about it, so likewise probably not worth the trouble if you're mostly interesting in BSC if you can deal with it in the XO instead....Unless you're doing it for asthetic purpose.

    Leave a comment:


  • zx82net
    replied
    Originally posted by billfitzmaurice View Post
    The advantage to a conical cabinet in the B&W fashion is reduction of internal reflection sourced response zits, because there are no parallel walls and no constant cross section. Being conical doesn't make it a transmission line, although a transmission line may be conical.
    Yep, that was what I was thinking,
    So in conclusion: Cone length does not need to be tuned to driver parameters. Instead, for a given volume of cone, it is probably best to determine the diameter-to-length aspect ratio based on baffle constraints. Sound reasonable?

    Follow on question: when it comes to minimizing baffle diffraction, any thoughts on what the ideal end profile is. I've called two options a toroidal-cap and a spherical cap, crude sketch of the cross-sections:
    Click image for larger version

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    Attached Files

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  • Steve Lee
    commented on 's reply
    Yup - a cone for a mid inside a cabinet would be about perfect and help with internal box reflections for the woofer in the same box . . .

  • zx82net
    commented on 's reply
    Thanks, I'll review

  • LIDAR
    replied
    IIRC someone at diyaudio.com did something like this but added variable rates of stuffing down the length of the cone. It seems to work well based on his findings. Again IIRC he used such a structure inside a conventional cabinet, so there's no disagreement with Olsen ;-)

    Leave a comment:


  • tvrgeek
    replied
    And as Olson showed, a driver in the end of a cylinder is the worst possible configuration. Like all baffles, radius the edge does wonders.

    The advantage for the B&W is sales bling and support to their profit margin. . The rest of us get buy with a well stuffed chamber.

    Leave a comment:

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