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  • Jim's new CBT Arrays

    Mr. Griffin contacted me recently and inquired about cutting/assembling some Array cabinets for him. He desired something similar to the "Epiques" but wanted to utilize a different driver (SB65WBAC25-4) along with make a few minor changes to the cabinets (1" wider, braces, roundovers). After a few emails back and forth, I presented him with a CAD model for approval and we started the project.


    I didn't take a lot of pictures during the build process, sorry guys. Jim did give me permission to post what I have for you to see. If you have questions about the cabs, I'll gladly try to answer. If it's about the details of the design and the "why's", Jim will chime in to answer those.

    Here are the CAD screenshots (in greyscale), not sure what color Jim will be painting the cabs. Believe he has a local painter in mind.

    Click image for larger version

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    One of the first hurdles would be coming up with a way to secure the removable baseplates to the towers. Jim was prepared to use bolts and nuts which would require him to be able to get his hands in through the back of the tower to start the nuts and tighten them. I suggested we look at incorporating a plate with nuts welded to them so he wouldn't have to do that. He liked the idea and after giving this some more thought, I suggested the plate be changed to a bracket with legs that could also be secured to the sidewalls. This would increase the overall strength of the assembly and spread out the work load. Had some 1/4" thick 3"x3" angle iron on hand and decided to use that. Overkill, yep. 1/8" steel would probably have sufficed but the extra weight at the bottom of the array isn't gonna hurt us.

    After cutting 1.5" off of two pieces of the angle iron, they were welded together and then milled flat on the bottoms. This was followed by drilling holes for 5/16" bolts, tapping the holes and then welding nuts for even more threads to engage with the bolts. Sandblasted them next and then applied a Rustoleum paint and primer in one.

    Click image for larger version

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    More in the next post.
    My "No-Name" CC Speaker
    Kerry's "Silverbacks"
    Ben's Synchaeta's for Mom
    The Archers
    Rick's "db" Desktop CBT Arrays
    The Gandalf's

  • #2
    This was one of the first pics I sent Jim as these were moving along. It showed the sidewalls, tops, braces, and bottoms all put together dry. The dado's worked well for aligning everything.

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    As I glued these together, I also applied an industrial epoxy to the brackets. The screws were more for alignment in the brackets, the glue will be doing all the work.

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    These taxed my clamp collection pretty good. I was surprised by how many it took to get the rear panel to conform.

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    More to come.
    My "No-Name" CC Speaker
    Kerry's "Silverbacks"
    Ben's Synchaeta's for Mom
    The Archers
    Rick's "db" Desktop CBT Arrays
    The Gandalf's

    Comment


    • #3
      After everything was glued together (minus the baffles), I mounted a base to the tower just to get a feel for how the plates worked. Everything felt really solid.

      Click image for larger version

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      Next up would be the baffles. I shared this photo of some test cuts with Jim and explained how a typical chamfer bit (cut on the right) would overcut the material left between the drivers. This had me nervous about breaking/cracking the baffles as I tried to conform them to the towers. The sample on the left is what I ended up going with. It was done on the CNC and is a 19 degree chamfer. Here's a link to the machine making those cuts. https://www.youtube.com/watch?v=wKRJoz_-WcU

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      After cutting the baffles, more glue and clamps.
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      Once those were dry, I turned the towers over and cut access holes for the shading boards. Jim is using the black anodized binding post plate from PE which has a nice thick gasket that will help in sealing it to the curved tower.
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      My "No-Name" CC Speaker
      Kerry's "Silverbacks"
      Ben's Synchaeta's for Mom
      The Archers
      Rick's "db" Desktop CBT Arrays
      The Gandalf's

      Comment


      • #4
        This was the last picture I got of the Arrays before starting on the packaging. They don't have the roundovers applied to the towers and bases in this pic but that was done right before shipping them out.
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        I spent a considerable amount of time on the packaging. Boxes had to be custom made, foam board cut to line the boxes and than polyethylene planks cut and placed for protection. They should arrive safe and sound but I know better than to guarantee it when UPS is involved. Wish us luck, they should be there by the end of the week!
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        Last edited by Kevin K.; 10-12-2017, 08:46 AM. Reason: typo
        My "No-Name" CC Speaker
        Kerry's "Silverbacks"
        Ben's Synchaeta's for Mom
        The Archers
        Rick's "db" Desktop CBT Arrays
        The Gandalf's

        Comment


        • #5
          Nice build! I have found making a .4x.4 "step" in place of the woofer hole chamfer works well and much easier to write the tool path.
          Are you using 3D software? I have been using Vcarve and I really like it.

          Comment


          • #6
            Great work and photos!

            I have started a parallel thread on the modified CBT24 design on the DIYaudio Full range forum at:


            http://www.diyaudio.com/forums/full-...ml#post5209947

            Comment


            • #7
              SB drivers never disappoint, in my opinion!

              Comment


              • #8
                Originally posted by xmax View Post
                Nice build! I have found making a .4x.4 "step" in place of the woofer hole chamfer works well and much easier to write the tool path.
                Are you using 3D software? I have been using Vcarve and I really like it.
                Thanks xmax. Yes, I'm using Think 3 for the modeling and Mastercam for the CNC toolpaths. Do you have a picture of what you are calling .4x.4 "step", not sure I follow, thanks.
                My "No-Name" CC Speaker
                Kerry's "Silverbacks"
                Ben's Synchaeta's for Mom
                The Archers
                Rick's "db" Desktop CBT Arrays
                The Gandalf's

                Comment


                • #9

                  Comment


                  • #10
                    I gotcha now, thanks for the pic. Yes, it would be considerably faster to cut the reliefs with that method. Not sure how well that would have worked out though in this situation with the drivers being as close to each other as they were.
                    My "No-Name" CC Speaker
                    Kerry's "Silverbacks"
                    Ben's Synchaeta's for Mom
                    The Archers
                    Rick's "db" Desktop CBT Arrays
                    The Gandalf's

                    Comment


                    • #11
                      Proper way to pack!
                      http://www.diy-ny.com/

                      Comment


                      • #12
                        Jim certainly knows his way around line arrays, so those should be awesome.
                        We're long overdue for an Atlanta DIY meeting.....hmm...

                        I think I hear a difference - wow, it's amazing!" Ethan Winer: audio myths
                        "As God is my witness I'll never be without a good pair of speakers!" Scarlett O'Hara

                        High value, high quality RS150/TB28-537SH bookshelf - TARGAS NLA!
                        SB13/Vifa BC25SC06 MTM DCR Galeons-SB13-MTM
                        My Voxel min sub Yet-another-Voxel-build

                        Tangband W6-sub

                        Comment


                        • #13
                          I'm no expert on line arrays and with all due respect, seemingly with all that Sd one could be designed with ample low end,
                          is there something with a line array that makes that not practical? I see subs are often recommend with them.

                          Comment


                          • #14
                            Xmax,

                            How many 2.5" drivers have you heard can produce impressive bass? Even 24 of them per side can not overcome physics. You can use EQ and
                            DSP tricks and do a half way job but a good pair of 12" or !5" woofers is an easy solution.

                            Jim

                            Comment


                            • #15
                              Don,

                              Have boxes. Will travel.

                              Jim

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