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Boom box build (another one, but first for me)

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  • Boom box build (another one, but first for me)

    Two converging events... I won a pair of ND105-PR at MWAF 2018, and my daughter (11) wants her own speaker.

    This is the plan.. a Sprite style box using the PRs instead of ports, all 4 cones up front will look awesome. Powered by the KAB 50W board and a battery pack. It will run at 12V so not too much power for the ND90-4 (bought on flash sale!).

    Construction will be from 1/4" stock and braced for lighter weight. I anticipate a lot of bondo since I'm not tooled for small cuts. Finish in white Duratex, tinted for some pink.

    Clever name TBD. My wife suggested Shia LeBoom LOL.
    Electronics engineer, woofer enthusiast, and musician.
    Wogg Music
    Published projects: PPA100 Bass Guitar Amp, ISO El-Cheapo Sub, Indy 8 2.1 powered sub, MicroSat, SuperNova Minimus

  • #2
    3"ers are (marginally) okay w/out a tweeter, but not the 4"ers. (Maybe your daughter won't mind, though.)

    Comment


    • #3
      Originally posted by Chris Roemer View Post
      3"ers are (marginally) okay w/out a tweeter, but not the 4"ers. (Maybe your daughter won't mind, though.)
      Agreed, and she won't ;) I plan on doing measurements and using a compensation filter for some baffle step and keeping the highs up as much as reasonable. The drivers are pointing about 16 degrees out either side for some spread. As long as it fills a room she'll be thrilled.
      Electronics engineer, woofer enthusiast, and musician.
      Wogg Music
      Published projects: PPA100 Bass Guitar Amp, ISO El-Cheapo Sub, Indy 8 2.1 powered sub, MicroSat, SuperNova Minimus

      Comment


      • #4
        Personally, ... mount the NDs behind the baffle. And if you have a router contour the cutouts. I think that looks sharp compared to the ND series mounted up front. For a more practical reason, the drivers will have a little more protection being recessed. Add some black, flat-head, Allen socket screws to mount them and you have a "manufactured" look.

        Below, see where I "doctored" the pic to show the recessed, flat-head screws. Better looking IMHO - very important to young women


        Click image for larger version

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        • #5
          Looks like a cool project. If you mount small drivers from the back, I would suggest #8 x 1/2" wood screws from the back, not visible from the front at all. Use flat washers if needed.

          I think you are on the right track with a simple contour filter, it shouldn't take much to get these drivers to cooperate. I expect the highs will be just fine also.

          Comment


          • #6
            Originally posted by Billet View Post
            I would suggest #8 x 1/2" wood screws from the back, not visible from the front at all.
            A very good idea as well.

            Comment


            • #7
              Originally posted by Billet View Post
              Looks like a cool project. If you mount small drivers from the back, I would suggest #8 x 1/2" wood screws from the back, not visible from the front at all. Use flat washers if needed.

              I think you are on the right track with a simple contour filter, it shouldn't take much to get these drivers to cooperate. I expect the highs will be just fine also.
              Yes, the half inch #8 screws from PE work great for rear mounting. I didn't have any go through, without using washers too.
              Click image for larger version

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              • #8
                Originally posted by amzounslide95
                I would look into two bookshelf sized high sensitivity speakers and integrate it into the box. Add a sub and a 2.1 plate amp.
                You must be a strong guy to be able to carry all that around with you
                Francis

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                • #9
                  Lesson (Mr. AmzoBOT), "bookshelf sized" and "high sensitivity" aren't often compatible.

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                  • #10
                    Originally posted by amzounslide95
                    I would look into two bookshelf sized high sensitivity speakers and integrate it into the box. Add a sub and a 2.1 plate amp.
                    Nope... missing the main point. I had the PR's on hand and have the rest of the materials ready to go. I like the idea of self powered bookshelves, but they're way less practical for a kid who wants music flexibility.
                    Electronics engineer, woofer enthusiast, and musician.
                    Wogg Music
                    Published projects: PPA100 Bass Guitar Amp, ISO El-Cheapo Sub, Indy 8 2.1 powered sub, MicroSat, SuperNova Minimus

                    Comment


                    • #11
                      Work area updated... time to actually move on these things. I re-did my Sketchup model to make the build practical. The electronics will be mounted vertically in the center with a 1/4" vent slot cut in the bottom front and rear top for a little air channel. Power, aux, and switches on the back, LED's and volume knob on the front. Volume looks like 0.12 cu ft for the drivers, just a tiny notch less than the Sprite design but really close. The PR's tune it high out of the box and should have no problem bringing the tuning down toward 60Hz. I'll mount the drivers from the back and use a small chamfer to make it pretty. I'll do a small chamfer around the top and bottom edges as well.

                      This drawing shows rabbet joints at the back, but I'm considering a 45 degree miter there as well.

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                      Here's what I'm thinking for my build process:
                      • Use a 1/2" x 6" appearance board from a big box store for the front / sides / back. Pondering oak or poplar. That lets me use my little miter saw for all cuts and utilize the already square edges of the board (5.5" actual dimension).
                      • Run a 1/4" rabbet around the top and bottom edges to mate with a MDF top and bottom panel
                      • Miter cut carefully, and glue up the outside edges first. Very important - this has to be SOLID for the next step to work
                      • Rough over cut the top and bottom panels and clamp them to the outside edge assembly
                      • Flush trim bit the MDF to match the edges exactly, easiest way to follow that 15 degree panel.
                      • Add the 1/4" rabbet to the MDF to drop it right in.
                      • Simple glue in separators
                      The top panel will be glued permanently, while I'll add threaded inserts to mount the bottom panel. I'm hoping #8 inserts will fit in the side of 1/2" material separators, haven't seen them to measure yet. I'll glue little slugs in where the panels meet for more material to grab since I can't put it in the 1/4" rabbeted area.

                      Once the cabinet is together I can tune the PR's and take measurements to plan the contour filter.

                      For finish I'm thinking keeping the solid wood visible with a light stain and seal around the outside with white Duratex on the MDF top and bottom. Sounds classy.
                      Electronics engineer, woofer enthusiast, and musician.
                      Wogg Music
                      Published projects: PPA100 Bass Guitar Amp, ISO El-Cheapo Sub, Indy 8 2.1 powered sub, MicroSat, SuperNova Minimus

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                      • #12
                        Nice idea wogg, can't wait to see this one. I'm.a huge fan of small enclosures and 0.12 per side is similar to one of mine

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                        • #13
                          Outside miters done. Used this little bugger to calibrate the angle on the saw, which was about 1/2" too small to make it all the way through the 5.5" board.

                          Click image for larger version

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                          Definitely need some sanding block action to get the edges lined up as tight as possible. I just wanted to tape it upright real quick to make sure my angle calculations were OK. Up next is routing the speaker and panel holes.

                          Click image for larger version

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                          Electronics engineer, woofer enthusiast, and musician.
                          Wogg Music
                          Published projects: PPA100 Bass Guitar Amp, ISO El-Cheapo Sub, Indy 8 2.1 powered sub, MicroSat, SuperNova Minimus

                          Comment


                          • #14
                            Lookin' good so far, you've got a nice shape there, it's pleasing to the eye.
                            This is one of those sketches that deserves to become a reality. You should make two though while you're at it, you may want one for yourself.
                            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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                            • #15
                              So no progress... and I'm a bit stymied on how to make the router cuts for the front panel. Also, last weekend was an impromptu trip to Cedar Point for a fun but disappointingly low coaster ride count. Looking for a little input on how best to do this.

                              The trouble is the 2 square cuts and the straight vent lines I've got planned for the front and rear panels.

                              Click image for larger version

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                              The plan is to use the router with a 1/4" bit, but I'm lacking the jig to capture the router and keep it in line. Options I can think of:
                              • Use a sacrificial board and cut the template with a jig saw, smooth it out and use a trim bit to match. Downside: I'll just be copying flaws from my jig saw to the finished product via flush trim.
                              • Fashion an outside the router template to guide around the squares. Downside: work to create the jig correctly, need some 1x2 stock or something to make it but could miter it together easy enough. I'll have to make 2 templates for the different size panel holes but could use just 1 side for the straight vent hole
                              • Clamp carpenter square down and use that for 1/2 of the hole at a time. Downside, super easy to overshoot the end without a stopper.
                              What am I missing... other options? I'm not very fancily equipped, so whatever I can do with hand held power tools, a basic miter and clamps will have to do.

                              The routing will generally be done up on a set of sawhorses with a sacrificial board and carpet tape to keep everything in place. I'll set it up as my make shift router table to do the rabbets and chamfers.
                              Electronics engineer, woofer enthusiast, and musician.
                              Wogg Music
                              Published projects: PPA100 Bass Guitar Amp, ISO El-Cheapo Sub, Indy 8 2.1 powered sub, MicroSat, SuperNova Minimus

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