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My 2 cents on Enclosure Joinery

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  • My 2 cents on Enclosure Joinery

    I really enjoy looking at speaker projects on this forum but I need to say that one thing that bugs me is the usage of b u t t joints. For example, when I see a speaker manufacture say "air tight cabinet sealed with silicone", what they are really saying is "our cabinets are built so poorly that we need to use silicone to fill all the gaps in the joinery".

    Not saying that you can't get a air tight cabinet with just b u t t joints and glue but *it is* more prone to being assembled poorly.

    At the very minimum I think you need to go with a rabbet/dado joint. This is a very simple joint made easily with dado blades on a table saw or even a bit on a router. Just glued and clamped, this joint will be air tight and strong and also assembles much neater. I built enclosures with this type of joinery for many years before graduating to lock-rabbet joints.

    Another thing is the usage of screws or nails. In my opinion this is entirely bad practice with proper joinery. A b u t t joint I do understand using screws as that is the only way it's ever going to stay together.

    I do realize that most of the projects here are home-audio and durability isn't a high priority but these are my feelings.

    I'm not recommending box joints or dovetails as I feel those on the other hand are overkill for speaker enclosures, also easy to mess up.

    Rabbet Joint:



    Lock-Rabbet Joint



    The lock-rabbet joint in my opinion is the best joinery for a speaker cabinet. Scary to cut sometimes as you have to cut a groove into the end of a panel. With a proper axillary fence though no problem.

    Just my opinions. Waiting to hear some of you fire back.

  • #2
    Re: My 2 cents on Enclosure Joinery

    For solid wood a but-t joint may not be so good - don't know, but for mdf it is more that good. Have you ever busted up an mdf cabinet? The mdf fails and not the glue joint.
    Brad
    piano black sealing mdf irregular recesses grill technique

    Comment


    • #3
      Re: My 2 cents on Enclosure Joinery

      Originally posted by killersoundz View Post
      I really enjoy looking at speaker projects on this forum but I need to say that one thing that bugs me is the usage of b u t t joints. For example, when I see a speaker manufacture say "air tight cabinet sealed with silicone", what they are really saying is "our cabinets are built so poorly that we need to use silicone to fill all the gaps in the joinery".

      Not saying that you can't get a air tight cabinet with just b u t t joints and glue but *it is* more prone to being assembled poorly.

      At the very minimum I think you need to go with a rabbet/dado joint. This is a very simple joint made easily with dado blades on a table saw or even a bit on a router. Just glued and clamped, this joint will be air tight and strong and also assembles much neater. I built enclosures with this type of joinery for many years before graduating to lock-rabbet joints.

      Another thing is the usage of screws or nails. In my opinion this is entirely bad practice with proper joinery. A b u t t joint I do understand using screws as that is the only way it's ever going to stay together.

      I do realize that most of the projects here are home-audio and durability isn't a high priority but these are my feelings.

      I'm not recommending box joints or dovetails as I feel those on the other hand are overkill for speaker enclosures, also easy to mess up.

      Rabbet Joint:



      Lock-Rabbet Joint



      The lock-rabbet joint in my opinion is the best joinery for a speaker cabinet. Scary to cut sometimes as you have to cut a groove into the end of a panel. With a proper axillary fence though no problem.

      Just my opinions. Waiting to hear some of you fire back.
      I think that the lock rabbet that you showed above is better for joining drawer faces to sides, where it hides the joint when looking at the face. ...a cheaper alternative to using half blind dovetails. I think it is overly complex for loudspeaker cabinets, and by that I mean the added complexity increases possibility for error in trade for little benefit.

      I think a rabbet shown below is good for MDF, dimensioned to half-thickness. Then break the edge with a radius or chamfer equal to that same half thickness dimension, placing the MDF edge material in that radius or chamfer (behaves differently than faces in finishing).



      Not sure what its called, but the joint below is very good for joining plywood box corners. It provides mechanical alignment, provides a lot of glued surface in the joint, and moves some of the stress away from the outside edge, less likely to crack/delaminate.
      "Our Nation’s interests are best served by fostering a peaceful global system comprised
      of interdependent networks of trade, finance, information, law, people and governance."
      - from the October 2007 U.S. Naval capstone doctrine
      A Cooperative Strategy for 21st Century Seapower
      (a lofty notion since removed in the March 2015 revision)

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      • #4
        Re: My 2 cents on Enclosure Joinery

        From my experience, rabbetts are good with mdf.
        The others not so much.

        Thin sections are not recommended with mdf and actually weaken the joint and are very vulnerable to damage during processing.
        Rule of thumb is do nothing for material under 5/8". Limit any section to 1/2 thickness of the stock or less.
        Avoid protrusions more than 1/3 the thickness of the stock.

        The plywood joint JRT shows (tongue and groove) is good for alignment purposes in MDF. Notice the tongue is rather stubby and set back from the edge more than 1/2 the thickness of the material. It would be better to reduce these dimensions even more for mdf.
        In ply this is a good joint and necessary for effective strength on something with a small glue surface like a drawer or small box.
        ~99%
        Make me an angel that flies from Montgomery
        Make me a poster of an old rodeo
        Just give me one thing that I can hold on to
        To believe in this livin' is just a hard way to go

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        • #5
          Re: My 2 cents on Enclosure Joinery

          I have built dozens of speaker cabs over the past few years from mdf, ply, and yes, even particle board. Almost all b*tt joint construction, some with biscuits. None have failed. The life of a speaker cabinet is pretty easy. It just sits there.

          Comment


          • #6
            Re: My 2 cents on Enclosure Joinery

            From the "strength" point of view, they are both good and better then bu.tt joints. From the "paint me" or "veneer me" point they both present the same set of problems unfortunately.
            http://www.diy-ny.com/

            Comment


            • #7
              Re: My 2 cents on Enclosure Joinery

              I appreciate your perspective, and I think it is worth the investigation. I have a few comments and questions.

              First, I agree with a previous poster that rabbet joints would seem to take away some of the inherent strength of MDF, which is near the surface. Below the surface, MDF is kind of like a flaky pastry.

              Second, I have to give some credit to but joints. I recently shipped a sub to a customer. The driver was damaged in shipping (the weight of the magnet sheared the basket apart), however the cabinet remained perfectly intact. The only joinery I used was but joints, glue, and brad nails.

              Third, what kind of joinery do they use to build pro audio cabinets? Those things take the most abuse by far--so whatever works for them is good enough for the rest fo the audio world. I used to be a professional stagehand and people do not handle that kind of gear gently.
              Isn't it about time we started answering rhetorical questions?

              Paul Carmody's DIY Audio Projects
              Twitter: @undefinition1

              Comment


              • #8
                Re: My 2 cents on Enclosure Joinery

                Butjoints all the way, baby. If you are capable of cutting a straight line and are not afraid of using a lot of glue, the joint (as noted above) is stronger than the material itself.

                Easy, quick, strong and no more difficult to finish than more exotic joining techniques. Does not require any tools besides a saw that will cut straight. I, for one, do not see the point is using anything "but" this type of joint. YMMV.
                Don't listen to me - I have not sold any $150,000 speakers.

                Comment


                • #9
                  Re: My 2 cents on Enclosure Joinery

                  MDF absorbs so much of the glue, you are actually bonding deeper than the surface. Plywood and solid wood needs better joinery.
                  .

                  Comment


                  • #10
                    Re: My 2 cents on Enclosure Joinery

                    Johnny has pretty much hit it. The but joint is a lot easier to get right. It takes much less time for measuring and setup. The rabbet requires significantly more operations and precision to accomplish, the lock rabbet even more.

                    The one thing I add to but joints for increased strength is biscuits. Easy to do, relatively immune to measurement precision, and much stronger than the surrounding material.

                    Having been a woodworker for many years, I can also understand that a but joint offends the cabinetmaker's sensibilities. However, as Paul points out, the but joint is more than strong enough for the intended purpose.



                    Originally posted by johnnyrichards View Post
                    Butjoints all the way, baby. If you are capable of cutting a straight line and are not afraid of using a lot of glue, the joint (as noted above) is stronger than the material itself.

                    Easy, quick, strong and no more difficult to finish than more exotic joining techniques. Does not require any tools besides a saw that will cut straight. I, for one, do not see the point is using anything "but" this type of joint. YMMV.
                    I was so much older then, I'm younger than that now.
                    OS MTMs http://techtalk.parts-express.com/sh...d.php?t=220388
                    Swope TM http://techtalk.parts-express.com/sh...d.php?t=221818
                    Econowave and Audio Nirvana AN10 fullrange http://techtalk.parts-express.com/sh...d.php?t=216841
                    Imperial Russian Stouts http://techtalk.parts-express.com/sh...=1#post1840444
                    LECBOS. http://techtalk.parts-express.com/sh...ghlight=lecbos

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                    • #11
                      Re: My 2 cents on Enclosure Joinery

                      As far as an air tight joint the **** joint superior. If you cut a straight line and apply glue to the entire joint it has to be air tight. As for any type of lap or tounge and groove joint there has to be some space in the joint to allow it to be assembled. Even thought the air would have to travel around the joint it is more likely to find a path. A **** joint with, properly applied glue, and properly clamped through the cureing process will always be stronger than any wood product even without mechanical fasteners.
                      Dovetail, tounge and groove and lap joints are all designed to use the mechanical friction of expanding wood to secure the joint and are superior where a joint is in danger of flexing, like an open top drawer. Glue will hold as long as it never moves and since a speaker cabinet needs to be air tight and rigid glue joints are perfect.

                      Comment


                      • #12
                        Re: My 2 cents on Enclosure Joinery

                        I use but*t joints with a continuous glue block along the length of the joint. I pin nail the glue block and then attach the adjoining face. That increases the surface area of the glue faces by 200% over a but*t joint.

                        It's all straight line rips and cross cuts. Clamps optional.
                        Mongo only pawn in game of life
                        ____
                        Ed

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                        • #13
                          Re: My 2 cents on Enclosure Joinery

                          What about miters? Seems like this would be at least as strong as a **** joint (even slightly more area) while solving the seam issue. I am surprised not to see more of this... Am I missing something? Are they that hard to get right? I've only used but t joints, but am strongly considering miters for my next project.

                          Comment


                          • #14
                            Re: My 2 cents on Enclosure Joinery

                            I made a set of speakers which were full mitered...one time. The machines must be dead-on accurate lest any variance get multiplied around the case.

                            In this case clamps were NOT optional...Filler was necessary.
                            Mongo only pawn in game of life
                            ____
                            Ed

                            Comment


                            • #15
                              Re: My 2 cents on Enclosure Joinery

                              I agree w/ Ed. Miter joints really are hard to get right. Once cut correctly, you would still want to use a spline or biscuit for additional strength.

                              For speaker use, your saw will have to be dead-on (unusual to the precision you need), blade flex can be enough to throw the joint off.

                              I have recently gotten a 45 degree chamfer bit for my router and am hopeful that will simplify the process.

                              Also, the miter joint will not be as good in mdf because you open up much more of the core. Mdf strength is mostly in the face, one of the reasons it doesn't hold screws as well as plywood.
                              I was so much older then, I'm younger than that now.
                              OS MTMs http://techtalk.parts-express.com/sh...d.php?t=220388
                              Swope TM http://techtalk.parts-express.com/sh...d.php?t=221818
                              Econowave and Audio Nirvana AN10 fullrange http://techtalk.parts-express.com/sh...d.php?t=216841
                              Imperial Russian Stouts http://techtalk.parts-express.com/sh...=1#post1840444
                              LECBOS. http://techtalk.parts-express.com/sh...ghlight=lecbos

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