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  • Light cabinet construction techniques?

    I fashioned a temporary 5^ft cabinet out of 3/4 MDF for a UM18 and it's really heavy. The original idea was to add raised panels to match the wainscoting in the room but I would have little chance to lift it, if I more than double the weight.

    I'm thinking about building a box out of 1/2", cover it with 1/2" foam, and then cover it with a weight reduced raised panel effect that is just glued on. The 5^ft box sounds good but I will back it down to 4.25^ft for additional weight saving. My goal is to get to 125#, including the speaker. This would be a stressed skin panel and it would be *really* strong.

    I'm also considering trying an outer box of 1/2" MDF, then build an inner box out of cardboard, and fill the gap between the box and cardboard using GreatStuff window and door foam. This isn't a joke. It might be an interesting experiment. My primary concern is rattling of the cardboard.

    Searching hasn't found any testing on light weight speaker enclosure construction. People seem to prefer heavy; the heavier the better. I did find a thread on cardboard enclosures on another forum, though.

    Any thoughts or advice? I'm just trolling for the kernel of an idea or to see if anyone has tried something to reduce weight which they might share, regardless of how successful the outcome was.




  • #2
    You can build with 1/2" plywood. That's what 90% of my speakers are made from. They're braced internally so that no other materials are needed. These aren't small boxes, either. They include pro-touring concert grade PA subs. The other 10% of my line up, which includes pro-touring PA mains, are made of a combination of 1/2", 1/4" and even 1/8" plywood. It's the bracing that makes it possible. Most people build cabs that resemble how an Abrams tank is constructed. Mine are more like an F-35, in no small part aided by all the balsa airplane models I made as a kid.
    www.billfitzmaurice.com
    www.billfitzmaurice.info/forum

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    • #3
      Whether 1/2" (as Bill recommends) or 3/4", you will reduce the weight significantly using plywood rather than MDF.

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      • #4
        My current subwoofer cabinet was built using 1/2inch plywood and it's been really sturdy feeling, so no regrets there.
        I was procrastinating moving the sub a while ago since just looking at it had me dreading the struggle. Finally went for it and was surpised to relearn how lightweight it is.

        The plywood is both lighter and stronger than MDF. Less...pungent when cutting it too. Costs nearly the same (sometimes cheaper since you can get away with thinner plywood without it being crumbly).
        My first 2way build

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        • #5
          I really appreciate the plywood idea, gentlemen. Thank you.

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          • #6
            My current speakers are made of ultra lightweight, foam filled, tile backer board. You can cut it with a craft knife, but getting a nice finish isn't easy. I just wrapped it in some vinyl flooring that I had left over.

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            • LOUT
              LOUT commented
              Editing a comment
              It looks kind of expensive and I imagine it'll flex and move more than wood when the subwoofer is booming away unless it's braced pretty thoroughly (also read that some brands are more flexible than others). How did you end up bracing it?

          • #7
            I built a beer cooler for brewing. Approximately 8 ft3. Large enough for two 6 gallon fermenting jugs. I built it out of home depot 2" white foam board. B u t t joints, titebond 3 glue. It's amazingly sturdy. I wrapped the edges with 1/8" masonite to prevent wear and tear.

            I needed a test box for a sub and built a 3/4" baffle for the cooler. Ugly but it works really well as a sub. I would have no hesitation in wrapping it with 1/8" veneered plywood for appearance.

            I don't need another sub now but am interested if anyone has had a similar experience. Downside of this material - Cutting the white board on a table saw was breeze but it produces a lot of tiny white beads that my dust vac system had real trouble collecting. This was 10 years ago and there is still evidence all over my shop.

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            • #8
              I could see using inch thick urethane foam with 1/8 inch facings on both sides, along with internal panel to panel bracing. The ultimate material is carbon fiber honeycomb, but it don't come cheap. A 24x36 inch piece of 3/4" carbon fiber faced Nomex core goes for $400. It only weighs four pounds.
              www.billfitzmaurice.com
              www.billfitzmaurice.info/forum

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              • #9
                Extruded polystyrene foam insulation comes in sheet sizes in thicknesses from 1/2" to 2". It is inexpensive and stiff. Like Bill said above, laminate it with 1/8 or 1/4" ply on each side, use reasonable internal bracing, and you could have some very rigid, very light speakers. I think the only reason we don't see this more is the effort involved in actually doing it.

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                • #10
                  Originally posted by billfitzmaurice View Post
                  I could see using inch thick urethane foam with 1/8 inch facings on both sides, along with internal panel to panel bracing. The ultimate material is carbon fiber honeycomb, but it don't come cheap. A 24x36 inch piece of 3/4" carbon fiber faced Nomex core goes for $400. It only weighs four pounds.
                  Well, aerogel would be lighter, but far more expensive. Like a couple of orders of magnitude more expensive.
                  It is estimated that one percent of the general population are psychopaths - New Criminologist: Understanding Psychopaths

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                  • #11
                    Originally posted by Dukk View Post
                    I think the only reason we don't see this more is the effort involved in actually doing it.
                    The flip side of that is why manufacturers use what seems like the heaviest possible materials with little to no bracing instead of lighter materials with bracing. As usual it comes down to cost. MDF is cheap, labor isn't.

                    www.billfitzmaurice.com
                    www.billfitzmaurice.info/forum

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                    • #12
                      Originally posted by billfitzmaurice View Post
                      The flip side of that is why manufacturers use what seems like the heaviest possible materials with little to no bracing instead of lighter materials with bracing. As usual it comes down to cost. MDF is cheap, labor isn't.
                      True that!

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                      • #13
                        I started testing these sorts of ideas recently: https://www.somasonus.net/box-construction-methods. Nothing definitive yet, but you might be interested in the results so far. So far I rather like results of joining simple 1/4" sheets of MDF with Weicon Flex 310M Classic construction adhesive.
                        ~Brandon 8O
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                        • #14
                          I was at the flower nursery today and saw a product made for making a pot of any size. It looks like corrugated plastic - kind of like egg crate but maybe 3/4" deep. In its intended use you wrap the sheet around and put a plastic disc at the bottom. The plastic was strong enough that I could stand on it without crushing it and it was very lightweight. I could see filling the "egg crate" with poly foam and sandwiching 1/8 plywood on each side. Would probably be very light and very strong.

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                          • #15
                            Thanks for the suggestions. I'm not trying to launch this thing into space, just keep it portable. I'm in my 50s and we plan to move cities in a couple of years. lol!

                            This plastic pot sounds interesting, for sure. It might make a terrific concrete form. If it could be corrugated on the inside, that might be a nice benefit. A little foam in the concrete will lighten it up somewhat.

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