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Next Project: Arc 40 CBT Array

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  • Next Project: Arc 40 CBT Array

    Per the title, next project in the works is an Active 40 degree Arc Array. Due to the cost of the arrays and equipment needed (stuff I still need to buy), am predicting this will take a few months to finance and complete.

    Was fortunate enough to meet Rick Craig at 2015 MWAF and then worked with him on a desktop CBT array for 2016's MWAF. While carrying in the speakers and equipment for the competition Friday night, low and behold Don Keele was cranking up his new CBT24's. To say I was floored would be an understatement. It's about all I could think about after MWAF and so I started pondering the idea of building some. After asking several forum members their thoughts on different drivers and driver combinations, Rick generously offered to help guide me along on the project. Lots to learn in between now and it's completion, and I'm not one to shy away from help when offered.

    Watched all of the videos Don has up on youtube about his CBT technology and briefed the links to his presentation papers. Still a whole lot of stuff in there I don't understand and hope to become more knowledgeable during this build. So, without further ado, let's get into some of the details for the project.

    Equipment Needed:
    MiniDSP 2x4
    A good Pre-Amp and 4-channel amplifier. Decided on Outlaw's Pre-amp & 5-channel Amp Combo. Currently on special for $999.00. Here are the links:
    http://www.outlawaudio.com/products/975.html
    http://www.outlawaudio.com/products/5000.html

    Drivers: 10 woofers and 20 tweeters per cabinet
    Woofers will be the SB Acoustics SB13PFC25-08 5" Paper Cone's, the same ones used in the Uluwatu's if you are familiar with those. Sorry guys, cant post the link, but you can look em up if interested.
    Tweeters will be the new Peerless DX20BF00-08 3/4" Textile Dome Tweeter - 8 ohm. Since PE carries Peerless products, I suspect these will be available from them soon.

    Cabinet Design:
    Sealed, 50 liters gross, 45 liter net after driver and brace displacements. Cabinets will be constructed from 1/2" MDF with multiple braces, damping material TBD. Sides, top, back & bottom will be veneered, baffle will be painted black. A grill may be incorporated to keep curious fingers off the drivers. Here is the first model of the cabinet:


    And the next images show some of the dimensions:



    I was nervous about the front baffle and the bend required for it to conform to the enclosure. With all of the driver holes cut, it seemed to me that it would be fairly easy to snap. Decided to cut a pair of sidewalls and one front baffle to either confirm my fears or put them to rest. It took shape remarkably well but had it been any thicker, not sure that would have been the case. Also, not a fan of ghosting so 45 degree chamfers were used and that seemed to help with the bend. All of the photos below show the baffle just clamped at the top and bottom of the enclosure, no glue, just a dry fit.




    And here is a pic with the drivers sitting in their pockets. Only have two each of the woofers and tweeters on hand right now, will get the rest when closer to finishing the enclosures.



    Now that the bend is no longer a concern, will go back to modeling the final enclosures with appropriate bracing and perhaps start the cuts on them next weekend. Thanks for looking guys.



    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
    awesome !
    Paper Towers
    RS180P/28F surrounds
    Boombox

    Comment


    • #3
      Wow Kevin! You are fast!
      https://www.facebook.com/Mosaic-Audi...7373763888294/

      Comment


      • #4
        Awesome. I'll be watching closely. With some of the drivers I get rid of I would really be interested in building something like these!!!

        Dan

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        • #5
          You are superman... Audio wise.... Hopefully, we'll get some listening impressions.

          Comment


          • #6
            CNCed, right?
            A mains
            The Ventures
            Open Invit8tions
            RSR
            Sound Troopers
            Acorns
            442
            DGBG's
            The Monuments

            Comment


            • #7
              Thanks guys.

              As for being fast, updates may be few and far between guys. I will try to keep them moving along as quickly as I can afford to. Almost everything about this project will be a learning experience for me, but one I look forward to, should be fun!

              Listening impressions Ani. If these are anything like Don's, you may never hear from me again. Show up to next years MWAF, you can hear them for yourself, hope you can make it.

              Dan, you have enough stuff to get started on some "Out of this World" arrays with that score you made recently. I'm betting there's even a few guys on this forum that would love to collaborate with you just to hear them. Best of luck!

              Eric, I love building speakers, but if I had to cut all of these holes in the baffles with a hand router, that might change from love to hate real fast. It still seemed like it took forever even on the CNC. Can't imagine doing it by hand but know it can be. There are lots of shops where this kind of work could be sub'd out and the pricing gets more and more reasonable all the time.

              Take care,
              Kevin
              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


              • #8
                Did you account for the curvature in the driver recesses when the panel is bent over the sides? The thickness of the rebate will change from driver edge to driver edge.

                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

                *InDIYana event website*

                Photobucket pages:
                http://photobucket.com/Wolf-Speakers_and_more

                My blog/writeups/thoughts here at PE:
                http://techtalk.parts-express.com/blog.php?u=4102

                Comment


                • #9
                  I looked at it both ways Ben. Decided to cut the test baffle as if it was for a flat enclosure. After bending the baffle to the sidewalls, I proceeded to mount a couple of the drivers. There was a slight mismatch on the tweeters where the baffle was just a smidge taller in the middle but I don't feel like it's enough to sweat. Surprisingly, there didn't appear to be any sign of it on the woofer. Maybe the strange shape of the top of SB driver has something to do with that?

                  I'll try to post a close up pic of the tweeter mounted tomorrow night so I can get feedback on whether you think this will be enough to be an issue.

                  Have a good one,
                  Kevin
                  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


                  • #10
                    Looking good Kevin, gotta love that CNC work! So you gonna do a subwoofer off that 5th channel? ;)
                    --
                    Javad Shadzi
                    Bay Area, CA

                    2-Channel Stereo system in the works with Adcom components and 4-way towers

                    Comment


                    • #11
                      Very interesting project, I hope to learn something from this thread.

                      Comment


                      • #12
                        re: What they said.

                        Here I was thinking that you'd spent dozens of hours of router work when in fact you were prob kicking back w a tall frosty while the CNC did the work. <grin>
                        Still, pretty monumental. Love those SB13 drivers. Gonna be awesome.

                        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
                          Wow, that looks really cool. I don't think I would have ever thought about mitering the corners on something like that with all that curving going on, but it seems to line up pretty much perfectly. That's a nice touch.
                          I wonder how it will act when there's some slippery glue between the joints though... Could I request you take a video as you glue the cabinet up? Maybe set up a Pay-Per-View? You can get Cole to 'bleep' out the bad words.... I'm just kidding, I bet it goes fine.

                          Thinking about the tweeters... I guess you could always drill three additional holes like some folks used to do on the "silkie" to get it to 'pull in' and lay flatter... or rather, curvier in your case. The plastic frame probably wouldn't mind the 'tweak' too much. Of course, that is like 7,492 extra holes you'd have to drill.
                          Where would you say the curviest part of the front is? It looks to be the middle section... like three woofers in from the top and bottom, but it's hard to tell.

                          Man, you sure like to jump right in the deep end of the pool... But being this far ahead for next year's MWAF I know you'll have it dialed in to perfection by then. Most arrays use 'decent' drivers, but not high end stuff because of the cost of multiples... but it looks like you're using some super-quality stuff. Just a two-way with those drivers would be impressive sound-quality wise.
                          I'm really looking forward to hearing these. I may have to get to Ohio a day early so I can actually stay for the Friday night 'Open Unlimited' class.

                          Just try not to spend ALL of your sons college fund, okay?

                          TomZ
                          *Veneering curves, seams, using heat-lock iron on method *Trimming veneer & tips *Curved Sides glue-up video
                          *Part 2 *Gluing multiple curved laminations of HDF *Cello's Speaker Project Page

                          *Building the "Micro-B 2.1 Plate Amplifier -- Part 1 * Part 2 * Part 3 * Part 4 * * Part 5 'Review' * -- Assembly Instructions PDF

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                          • #14
                            Looked at the specs and FR graphs for those drivers...Will you be posting details of the signal treatment settings used with the DSP?
                            "Not a Speaker Designer - Not even on the Internet"
                            "If the freedom of speech is taken away, then dumb and silent we may be led, like sheep to the slaughter."

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                            • #15
                              Originally posted by philthien View Post
                              Very interesting project, I hope to learn something from this thread.
                              Me too!
                              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

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