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  • baby boomer build blog

    Hi all,

    I haven't posted in a while. Not sure if build logs belong more in techtalk or the speaker gallery forum these days.
    If I should move it, please let me know.


    Anyway, I've decided to build a subwoofer and after much deliberation settled on Jeff B's Baby Boomer. I figure i would document the process here. This is my first project in a while, so I'll also ask some questions along the way.

    Interesting side note: because my home does not allow for much shop space, I joined a local "maker space" which has a well appointed communal wood-shop. It was pretty awesome using a sawstop with a huge outfeed table, commercial grade dust collection, etc. I'll try to fit in some picture of the space as I go along.


    Day #1:

    Yesterday I got the mdf cut to size and made the cut-outs for the passive radiators and the subwoofer driver.
    Pictures of the progress attached (will work on making future images higher quality).

    Pile of cab sides (a few extras in case I mess up)
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    Woofer cut-out
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    Passive radiator cut-out
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    A few questions for the group:

    1. I hate t-nuts and swore them off after my last build. I'm not the type to uninstall drivers frequently. My hope is that this will be a sub that I build, put in a corner of my media room, and let it do its thing for years. The passives are light and I think the #8PE black oxide screws will be fine. The sub driver is heavier but not a monster (Dayton Classic DCS-255). Because of the deep rabbet required there is about 3/8" of MDF to mount into. What do you think? Will #10 black oxide screws be enough or should I consider #10 bolts with nuts and washers?

    2. Do people think that the gasket material on the back of the driver is adequate, or do you supplement with additional gasket for air-tightness?

    3. Anyone have a strong preference for sealant around the inside corners of the cabs and the amp? I've just used whatever silicone I pickup at the hardware store in the past.


    Thanks,
    Mike

  • #2
    Re: baby boomer build blog

    Originally posted by mtmpenn View Post
    A few questions for the group:

    1. I hate t-nuts and swore them off after my last build. I'm not the type to uninstall drivers frequently. My hope is that this will be a sub that I build, put in a corner of my media room, and let it do its thing for years. The passives are light and I think the #8PE black oxide screws will be fine. The sub driver is heavier but not a monster (Dayton Classic DCS-255). Because of the deep rabbet required there is about 3/8" of MDF to mount into. What do you think? Will #10 black oxide screws be enough or should I consider #10 bolts with nuts and washers?

    2. Do people think that the gasket material on the back of the driver is adequate, or do you supplement with additional gasket for air-tightness?

    3. Anyone have a strong preference for sealant around the inside corners of the cabs and the amp? I've just used whatever silicone I pickup at the hardware store in the past.

    Thanks,
    Mike
    1. I would back the MDF with plywood cleats, just a glued in square 1"x1" would be fine, it will give the screws more to grab into. I have used this process and taken a sub out 4-5 times without any issue. I would use at least a 1-1/2" coarse thread screw though.

    2. Try it without and if it whistles at you, add some window gasket from HD. I use 3/8" wide and one that compresses to 1/16" or less.

    3. I personally use silicone across all the seams in a subwoofer because of the pressure the box will see. Again, you could try without and if you notice any leaks, seal it up. With two cutouts it would be easy.

    You're going to love the sub, I have a similar design with the 8" woofer and it's nice, so it's big brother should be very competent. Keep the pics coming!
    Paul

    The "SB's" build page
    http://techtalk.parts-express.com/sh...-4-(pic-heavy)

    Comment


    • #3
      Re: baby boomer build blog

      Originally posted by bullittstang View Post
      1. I would back the MDF with plywood cleats, just a glued in square 1"x1" would be fine, it will give the screws more to grab into. I have used this process and taken a sub out 4-5 times without any issue. I would use at least a 1-1/2" coarse thread screw though.

      2. Try it without and if it whistles at you, add some window gasket from HD. I use 3/8" wide and one that compresses to 1/16" or less.

      3. I personally use silicone across all the seams in a subwoofer because of the pressure the box will see. Again, you could try without and if you notice any leaks, seal it up. With two cutouts it would be easy.

      You're going to love the sub, I have a similar design with the 8" woofer and it's nice, so it's big brother should be very competent. Keep the pics coming!
      +1 to the above. I normally use wood glue to seal the the seams during assembly and haven't had an issue, and I'm sure caulk or silicone will also be fine.

      Comment


      • #4
        Re: baby boomer build blog

        Originally posted by mtmpenn View Post
        Hi all,
        ...

        Interesting side note: because my home does not allow for much shop space, I joined a local "maker space" which has a well appointed communal wood-shop. It was pretty awesome using a sawstop with a huge outfeed table, commercial grade dust collection, etc. I'll try to fit in some picture of the space as I go along.
        ...
        Thanks,
        Mike
        I think I'm more interested in this local makerspace workshop. Since I moved last April, my tools have been moved into an outdoor shed. And even before the move, my garage was dis-organized and only had a small contractor saw. A big stop saw with roll out table would be nice.
        Where are you located? And is there a good website to find places like this?
        - 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

        Comment


        • #5
          Re: baby boomer build blog

          Ive always just used an extra bead of wood glue on all the seams and havent had a failure yet. I always use a 3/4 inch and 1/2 sandwich mdf for 1-1/4" baffle because of the recess.

          The screws are fine however the woofer frame is kinda thick so you dont have much thickness to grab on too. If you have atleast a 1/4" thick left i would consider trying it. You could also use dowel rod and cut pieces off and wood glue/hot glue them on the inside of the baffle screw holes. Size the dowel accordingly so you have some wiggle room if its not perfect. You can use super glue on the screw to make them "maintain the threads better" and if you blow one out insert a few toothpicks with wood glue in the screw hole then drill a pilot hole back in it!
          My Build Thread's
          Carrera's / Finalist TL's / Speedster TMM's / Speedster MTM Center / Overnight Sensation Surrounds

          Comment


          • #6
            Re: baby boomer build blog

            Thanks guys. I appreciate the suggestions.

            I really like the idea of gluing some plywood or hardwood cleats to the back of the woofer cut-out to give the screws a little something extra to bite into.
            I'll see what I can find in the scrap pile and probably proceed in that direction.


            ---K---

            I'm in downtown Philadelphia. I found the place that I joined (NextFab Studio) because it is located near my home. In addition to NextFab, Philly also has a membership based wood shop (Philadelphia Woodworks), but that is a good bit further from my place. I don't know how to search for places in other cities, but so far my experience has been very positive. Membership at NextFab is not cheap, but it opens up a range of work that is otherwise completely impossible given that I live in a very small city home with minimal space to work or store equipment. Also, if I am feeling adventurous in the future there is a full metal shop, 2 shop bot CNCs, and multiple 3D printers available and classed where I can learn how to use all of those tools. Pretty cool... Now I just have to see if I can carve out enough time to actually go there and enjoy it.

            Mike

            Comment


            • #7
              Re: baby boomer build blog

              Originally posted by ---k--- View Post
              I think I'm more interested in this local makerspace workshop. Since I moved last April, my tools have been moved into an outdoor shed. And even before the move, my garage was dis-organized and only had a small contractor saw. A big stop saw with roll out table would be nice.
              Where are you located? And is there a good website to find places like this?

              Comment


              • #8
                Re: baby boomer build blog

                Today I made a little bit of progress.

                1. Based on advice above, I glued some plywood pieces to the inside of the carcass walls. This way I can mount the drivers using screws and have a little extra meat for the screws to adhere to.


                2. Glued up the panels into a cube. I considered using my domino or a biscuit joiner to help with panel alignemnt, but ultimately decided on **** joints. The shop only has two 90 deg clamps and I was in a hurry though so decided to do it free hand. I think it turned out just fine. One of the panels is a little bit out of position, but nothing that a little sanding won't take care of.

                Also, I left two of the sides oversized. This was done on purpose. I'll use a flush trim bit to take of the excess later.

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                • #9
                  Re: baby boomer build blog

                  Also, some expressed interest in the idea of a maker-space, so a few shop images.

                  Sorry they are not the best, but I wanted to be respectful of other people who were working.

                  Table saw (1 of 2)
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                  Band Saws and Drill Press
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                  Sanders
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                  Shot Bots
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                  • #10
                    Re: baby boomer build blog

                    Some more progress pics.

                    Used some silicone caulk on the interior corners to make sure it was air tight.

                    Then used a flush trim bit to flush up the 2 oversized panels.

                    I am planning for magnetic grills so I also measured, marked and drilled some holes for those.
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                    I epoxied the magnets in place, then used some wood filler over top.
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                    I am working on matching grills. I'm hoping to use 1/4" plywood for the grills. I'm not sure if it will be solid enough once the woofer holes are cut in them, but I am cautiously optimistic. I wanted the magnets to be proud of the grills so that there would be some space between the baffle and the grill. Because I didn't have an appropriately sized forstner bit I used a brad point bit to make the holes. As a result they are not totally flat on the bottem and so the magnets are a little askew. I am hopeful this won't be a problem in the end. The plywood is flexible so will probably just bend a little to account for this, which I think will be okay.

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                    Things are starting to take shape. Next steps:
                    - Amp cut-out
                    - Drill pilot holes for rubber feet
                    - A little work cleaning up the grills, then cut holes in them
                    - More surface prep (have sure filler looks good, then sand up to 180)
                    - Painting

                    I'm dreading the painting part. Current plan is shellac based primer, then rustoleum filler/primer, then white, then clear.

                    Comment


                    • #11
                      Re: baby boomer build blog

                      A question for those with more experience:

                      How do you sand your round-overs? I have just used my hand wrapped around the sandpaper in the past, but sometimes this can makes small, slightly noticeable flat spots. I also notice that sanding the faces of the cabinets flattens out the round-overs a little bit, so I end up having to try to sand this out.

                      Any tips/tricks to make this smoother (pun intended)?

                      Comment


                      • #12
                        Re: baby boomer build blog

                        Originally posted by mtmpenn View Post
                        A question for those with more experience:

                        How do you sand your round-overs? I have just used my hand wrapped around the sandpaper in the past, but sometimes this can makes small, slightly noticeable flat spots. I also notice that sanding the faces of the cabinets flattens out the round-overs a little bit, so I end up having to try to sand this out.

                        Any tips/tricks to make this smoother (pun intended)?
                        I also just hand-sand roundovers. If you're getting flat spots, maybe try less pressure, a finer grit, and also not repetitively sanding with the same direction stroke. There is still some "blending" needed between the flat and the roundover to get a smooth transition, because any sanding is going to remove material.

                        Comment


                        • #13
                          Re: baby boomer build blog

                          There are sanding blocks available with various profiles for sanding curves and such. Check with some of the wood specialty suppliers like Rockler.

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