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  • Box Construction Idea: What's your opinion?

    Dan N.

  • #2
    Re: Box Construction Idea: What's your opinion?

    If you were having problems with panel resonance then this might be a possible solution. If you varied the spacing and size of the fins and were able to bond them incredibly well.

    I don't see how it would make the box more rigid...
    I would expect a bit less rigidity with all those slots in the walls interrupting an otherwise homogeneous panel. Fitting and bonding the fins well enough is the issue.

    If you were able to mold a homogeneous panel with all those fins then, yes, it would be more rigid.

    The fins would probably occupy more volume than a more traditional approach to bracing, which means no weight or volume savings if material density is the same.
    But with the right material and fin shape and wall thickness you could make a more rigid, greater volume, lighter weight box.
    ~99%
    Make me an angel that flies from Montgomery
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    • #3
      Rib bracing and other musings

      Yes, this would make the box more rigid, and would be even better if you tied the "rib" bracing that you have drawn on each side to the same rib on the opposite side across the back and front (where you can) with another rib. You might consider using 1/8" hardboard for the ribs since it is stiff in-plane, cheap and you could easily rip lots of little strips on a table saw.

      I always had the idea that bracing the corners of the cabinet was not useful because the corner is self-bracing and it is more the free middle of the panel that is available to resonate. Don't quote me on that one however! Another idea I almost tried (but it was too expensive for me at the time) was to purchase some single-sided honeycomb panels and use these for the sides of a loudspeaker with damping material sprayed into each comb.

      I seem to recall reading a relevant note about bracing versus damping on this page of Art Ludwig's excellent web site. The general conclusion was that bracing only helped at the lowest frequencies and that panel internal damping was more important above 100Hz. Its a highly recommended read!

      -Charlie
      Charlie's Audio Pages: http://audio.claub.net

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      • #4
        Re: Box Construction Idea: What's your opinion?

        Make the vanes deeper, with varied spacing between them, and you have the original acoustic labyrinth of the 1950s, not to be confused with Stromberg-Carlson's 1/4 wave pipe of the same name.
        There's very little you can do with respect to enclosure design or construction that hasn't been done already. A few hours spent perusing the US Patent Office site is a real eye opener. You won't believe how far this art had come by 1930.
        www.billfitzmaurice.com
        www.billfitzmaurice.info/forum

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        • #5
          Re: Box Construction Idea: What's your opinion?

          Hi Dan,

          I agree that a ribbed panel will be much stiffer than one without.
          But wouldn't adding all that mass, in the form of ribs, without tying them to other panels often, decrease the resonant frequency of the panel, possibly back into the passband?

          I guess the question would be- does the panel with ribs act as one resonating panel, or do the individual vanes act as multiple resonating panels within the larger panel.

          I'm just thinking out loud.

          Greg

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          • #6
            Re: Box Construction Idea: What's your opinion?

            There are some good thoughts from everyone so far. I like the idea of trying 1/8" hardboard, since it would take a single kerf cut from a table saw to make a slot for it. It is denser than mdf, so that might be an improvement. I'm not sure if it is lighter than 1/4" plywood. I agree, you would certainly want to tie one side of the box to the other side with perhaps 1"x2" braces, but the fins have a side benefit of giving you some surfaces, other than just the end of the brace to glue to. My thinking is that the fins, combined with a couple cross braces side to side and front to back could be quite effective, yet lightweight and perhaps a little less volume used. The side to side tie is needed to keep the wall panels from flexing both in and out under pressure. As long as the fins were glued in with liberal amounts of glue, I wouldn't think the side panels would be weakened by the kerf cuts.

            I agree Charlie that the corners are already adequately braced naturally, so the need is greatest at the center of the panels. Maybe the fins would be most effective is spaced closer together in the center and then increasing further apart as you get to the corners. I just may have to experiment with this on my next project.

            I wonder if the fins would have any effect on reflections bouncing around inside of the cabinet in a ported system, good or bad? I wonder which direction woujld be most effective for running the fins? I guess if it is ported, you might want them running in the direction of the air flow from the driver to the port. On the other hand, you might want the fins position such that sound off the back of the driver is hitting the ends of the fins not the sides. In a typical box that might mean side fins are horizontal and back and front fins are vertical. I guess it would not matter in a seaed system.

            What do you guys think?
            Dan N.

            Comment


            • #7
              Re: Box Construction Idea: What's your opinion?

              Originally posted by dlneubec View Post
              There are some good thoughts from everyone so far. I like the idea of trying 1/8" hardboard, since it would take a single kerf cut from a table saw to make a slot for it. It is denser than mdf, so that might be an improvement. I'm not sure if it is lighter than 1/4" plywood. I agree, you would certainly want to tie one side of the box to the other side with perhaps 1"x2" braces, but the fins have a side benefit of giving you some surfaces, other than just the end of the brace to glue to. My thinking is that the fins, combined with a couple cross braces side to side and front to back could be quite effective, yet lightweight and perhaps a little less volume used. The side to side tie is needed to keep the wall panels from flexing both in and out under pressure. As long as the fins were glued in with liberal amounts of glue, I wouldn't think the side panels would be weakened by the kerf cuts.

              I agree Charlie that the corners are already adequately braced naturally, so the need is greatest at the center of the panels. Maybe the fins would be most effective is spaced closer together in the center and then increasing further apart as you get to the corners. I just may have to experiment with this on my next project.

              I wonder if the fins would have any effect on reflections bouncing around inside of the cabinet in a ported system, good or bad? I wonder which direction woujld be most effective for running the fins? I guess if it is ported, you might want them running in the direction of the air flow from the driver to the port. On the other hand, you might want the fins position such that sound off the back of the driver is hitting the ends of the fins not the sides. In a typical box that might mean side fins are horizontal and back and front fins are vertical. I guess it would not matter in a seaed system.

              What do you guys think?
              I will add that the 1/8" hardboard I've used is *actually* 3/16" thick. This may put a hindrance on the single-kerf application.
              Later,
              Wolf
              "Wolf, you shall now be known as "King of the Zip ties." -Pete00t
              "Wolf and speakers equivalent to Picasso and 'Blue'" -dantheman
              "He is a true ambassador for this forum and speaker DIY in general." -Ed Froste
              "We're all in this together, so keep your stick on the ice!" - Red Green aka Steve Smith

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              • #8
                Re: Box Construction Idea: What's your opinion?

                I have some out in the garage, so I'll check it out as compared to a saw cut. Thanks for the heads up.
                Dan N.

                Comment


                • #9
                  Re: Box Construction Idea: What's your opinion?

                  Dan,
                  A few years back I actually did some quick Finite Element Models of what your showing and compared it to double thickness of the sides. My models showed that the braces were more effective than double thickness at reducing panel deflection. But, there are a ton of variables, so YMMV.

                  What I see when I see something like that is the same structural concepts of a steel wide flange section or an angle. The talk about using 1/8 hardboard instantly brought to mind those cheep floor joists that you can buy with a 2x4 top and bottom plate with usually 3/8 web. They are incredible strong for their weight.

                  If you think about a simple plate it bends pretty easily. If you add a leg to form an angle, it gets a lot more difficult to bend. The longer the leg, the more difficult to bend. You're increasing the moment of inertia of the panel, which is directly related to the deflection. I'm going to stop before I bore you all with engineering garbage...

                  But, the longer you make your fins (I=1/12bh^3), the more effective they will be. If you make them Tees they would be even more effective.

                  How much of this is needed??? No clue.
                  - Ryan

                  CJD Ochocinco ND140/BC25SC06 MTM & TM
                  CJD Khanspires - A Dayton RS28/RS150/RS225 WMTMW
                  CJD Khancenter - A Dayton RS28/RS150/RS180 WTMW Center
                  CJD In-Khan-Neatos - A Dayton RS180/RS150/RS28 In/On Wall MTW

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                  • #10
                    Re: Box Construction Idea: What's your opinion?

                    Dan,

                    I'll admit to start this is entirely a S.W.A.G., so here goes:

                    The fins don't need to be rectilinear. The edge out in the box could (maybe should) be curved. The need for stiffening, and from that the need for the greatest section of the fin occurs at its mid-point.

                    Choose the 1st "fin" to be located by the golden ratio...divide the side dimension by 1.618 and place it that far away from the baffle on the side panel.
                    Choose the 2nd "fin", slightly less in section (height), and locate it in the largest portion of the 1st divided panel. That would be back towards the driver, closest to the baffle.

                    Choose the 3rd "fin", slightly less in section from the second and use it to subdivide the other portion of the 1st subdivided panel.

                    You now have 3 "fins" of different heights which divide the side into 4 unequal segments. This greatly reduces the chance for resonances. This process could be repeated indefinitely. You will get to a point of diminishing returns....can't say where that is...
                    Mongo only pawn in game of life
                    ____
                    Ed

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                    • #11
                      Re: Well, Bill, while we have your attention...

                      Originally posted by billfitzmaurice View Post
                      Make the vanes deeper, with varied spacing between them, and you have the original acoustic labyrinth of the 1950s, not to be confused with Stromberg-Carlson's 1/4 wave pipe of the same name.
                      There's very little you can do with respect to enclosure design or construction that hasn't been done already. A few hours spent perusing the US Patent Office site is a real eye opener. You won't believe how far this art had come by 1930.
                      I do find it interesting how you know so much history about cabinet design. So if I could tap your brain for a few minutes here... do you have have any info (or links) to interesting bracing or damping methods used over the years.

                      In your honest opinion, at what point did cabinet designers "get it right," and what method was that?

                      Thanks.
                      Isn't it about time we started answering rhetorical questions?

                      Paul Carmody's DIY Audio Projects
                      Twitter: @undefinition1

                      Comment


                      • #12
                        Re: Well, Bill, while we have your attention...

                        Originally posted by undefinition View Post

                        In your honest opinion, at what point did cabinet designers "get it right,"
                        Between Harry Olson, Paul Klipsch, James Novak, Ed Villchur, Henry Kloss and Roy Allison all the bases were pretty much covered by 1960. Most of what has happened since then is directly attributed to improvements in drivers. The cabinets that those guys didn't build wasn't for lack of knowledge but for lack of drivers that would work in them.
                        Harry Olson alone accomplished as much as all the rest combined and served as their mentor.
                        www.billfitzmaurice.com
                        www.billfitzmaurice.info/forum

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                        • #13
                          Re: Box Construction Idea: What's your opinion?

                          Ed,

                          What you and othere have suggested makes sense. Make the fins the deepest in the middle, vary the size and place them at the golden ratio with regards to one another and the box sides. I would think the number of fins would naturally need to increase as box size increases.

                          I may just try this in my BaSSlines project.
                          Dan N.

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                          • #14
                            Check out my ribbed box layout

                            Ok, I've taken a shot a drawing up a ribbed box design for my BaSSlines project. It uses 1/8" hardboard ribs. They vary in depth from 1" toward the outside of the box and increase in 1/4" increments up to 2" at the center, not including the 1/4" they are dado'd into the box. There are 5 ribs on each side. the ribs are tapered so that they are full depth at the center, but narrow to 1" deep at the box edges. Here is how I arranged them.

                            Since the center of the box is where the support is most needed, I started with a rib there. Then I determined the distance to the side of the box from this central rib. I divided that by 1.618 and established the second rib at the golden mean distance toward the side from the center rib. The third rib was then located that same GM distance, only it was measured from the side, not the center rib. I applied the same pattern for establishing the next two ribs. I'm sure this description is impossible to follow, but it might be clearer when compared to the drawing below. This was done to the sides, top, back and partially on the front baffle. Nothing was applied to the bottom because I thought the slot port construction offered enough rigidity.

                            After establishing the rib locations, I added hardwood bracing to tie the opposite sides together. There are 2 side to side, 2 front to back and 1 from a side-side cross-brace tieing to the top.

                            What do you all think?

                            Dan N.

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                            • #15
                              Re: Box Construction Idea: What's your opinion?

                              Looks good...I think you'll (we'll) like it. The taper of the bass bin walls is a benefit to killing resonances as well.
                              Mongo only pawn in game of life
                              ____
                              Ed

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