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Speaker Cabinet Materials: Beyond MDF

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  • Speaker Cabinet Materials: Beyond MDF

    I have been toying around with what a cabinet could be constructed from, something besides old faithful MDF and was curious if anyone had tried them.

    First up, HDPE (Same stuff as most plastic cutting boards). It seems to be relatively inexpensive at least compared to Aluminum, and is proposed to be easy to machine. I have a cutting board made of it at home which is only 5/8 thick and it is very stiff and quiet inert. I have seen it on Ebay in 3/4 and 1" thicknesses, seems like it could be an option, and the molded-in color and high resistance to damage are nice positives. Any thoughts?

    Next up Aluminum, probably not ideal for an entire cabinet but for a baffle and perhaps top and bottom panels? Could use HDPE sides and aluminum for the other panels perhaps...lots of high-dollar speakers are going to it and I have knuckle wrapped a few of them and been very impressed by its inert nature. Anyone experimented with using it? Machining is an issue as is of course cost, and I would think you would need some dampening to keep resonances from popping up, perhaps with bracing made from MDF or another dissimilar material would help as well...

    How about Baltic Birch? I know this isn't a very new idea, but the translam method with this product seems to have good results. Negative is difficulty in assembly of the layers as well as extreme waste of material when cutting out the slices. I like the Magico Aluminum baffle/Baltic cabinet method though this would be a pretty expensive cabinet to build as well.

    Lastly- composites, specifically carbon fiber/fiberglass. I know many car audio boxes use this but it is more out of necessity than performance in many cases. Issues would include sufficient thickness to get adequate stiffness and dampening as well as again cost. In addition it doesn't give much material for joining a baffle to, and I would think you would need to be somewhat creative with the design to make it easier to lay-up. Anyone messed with this stuff?

    Cheers,
    Sam

  • #2
    Re: Speaker Cabinet Materials: Beyond MDF

    A friend of a friend made molds and poured concrete :eek:

    Never saw them, but apparently they were amazing.
    Form does not follow function
    Form is simultaneous to function

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    • #3
      Re: Speaker Cabinet Materials: Beyond MDF

      my question would be if there is a specific reason why you would want to deviate form mdf or ply. Both i think are fine for speaker building. I like mdf for painting for veneer and ply for pro boxes, or carpeted ect.
      Anyway to answer your question about composites: I have worked with it quite a bit as it pertains to the aviation world. Best strength to weight is fiber core fiber. And each kind of fiber has it's advantages and disadvantages. I would think for a speaker that regular e-glass would be fine. How to build one?? I would make a foam core of the inside volume, then glass, core glass. Cut your holes for the speakers, then dig out the inside core you made. Some cores will desolv with solvents. Be pretty light and stong... i see no downside. You would want to vacuum bag that though. Do some reading on that topic.
      As for the car boxes like that.... the show ones are a fiberglass trim panel, and usually not a box. JL stealth boxes are glass, but they use chop mat and are THICK!
      You could do a combination of glass and wood.
      Isn't that what's so great about DIY?! Sky's the limit!

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      • #4
        Re: Speaker Cabinet Materials: Beyond MDF

        Well to answer the question about why, first would be to find a higher performance material, second would be aesthetics. Anodized aluminum, carbon fiber, these are gorgeous to look at, even better than a nice veneer in some cases though I know everyone has their own tastes....

        I have found also that making an MDF cabinet that is well damped requires it to be almost ridiculously heavy (especially in the case of subs, mine weighs in at 80lbs without an amp). Using other materials could perhaps provide similar stiffness and density without the weight.

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        • #5
          Re: Speaker Cabinet Materials: Beyond MDF

          Forgot, also you could be more creative with the shape and design potentially as well...

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          • #6
            Re: Speaker Cabinet Materials: Beyond MDF

            I've been intrigued by Vance Dickason's designs using 1/2 of a large sono-tube to form a 1/2 cylinder behind the drivers. He then fills the voids behind the sono-tube and the sides and back of the cabinet with dry sand.

            I think he lines the driver side with an acoustic damping material or stuffs the driver side with Acousti-Stuff as needed.

            I realize it isn't light, but it's probably one of the deadest construction methods I've seen. I'd think you could back off on the back & side panel thickness quite a bit...

            Jay T
            Jay T
            http://sites.google.com/site/lhwidgetssite/home

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            • #7
              Re: Speaker Cabinet Materials: Beyond MDF

              If the overall goal is stiffness, do some research and find an economically viable material with the highest modulus of elasticity (red oak is a good candidate.) Carbon fiber is near the top, and you might have a hard time finding boron. That being said, even common old glass fiber has a significantly larger longitudinal modulus than most woods I've encountered.

              However, it seems there might be something to be said for sheer mass. I have a little sub I built out of 0.5" ply, adequately braced, that vibrates. I think it is stiff enough, but I don't think it has enough mass. Vibrational dynamics is something I've been meaning to look into for a while.

              Another caveat; just because you are using a high quality material doesn't mean you should neglect good engineering bracing techniques. Just as an example, if I recall right, Linkwitz recommends keeping the distance between bracing less than ~4" to push the resonant frequency of the panel up past the passband of the woofer.

              I think an MDF box braced with red oak and veneered with faux carbon fiber (a black glass fiber in a twill weave) using a simple polyester resin is about as good as you need to get.

              I'll post pictures when I'm finished. :D

              Greg

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              • #8
                Re: Speaker Cabinet Materials: Beyond MDF

                Sonic aspects aside there are three main qualities desirable of a material for speaker building: reasonable cost, ease of machining/cutting and ease of joinery. MDF and plywood have all three. Exotic materials tend not to have any of these qualities, let alone all of them.
                www.billfitzmaurice.com
                www.billfitzmaurice.info/forum

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                • #9
                  Re: Speaker Cabinet Materials: Beyond MDF

                  Originally posted by gregrueff View Post
                  and you might have a hard time finding boron. Greg
                  Ya' think? And there I was planning to melt down all those Denon phono cartridge cantilevers I had laying around. :rolleyes:
                  Building it big and playing it loud! Because we all know size really does matter, and a little over compensation never hurt anyone. :eek:

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                  • #10
                    Re: Speaker Cabinet Materials: Beyond MDF

                    It's a fun thought exercise, but lets face it: if a good old well braced MDF speaker enclosure is the limiting factor in your audio system, you have all of us beat by a long shot!

                    -David

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                    • #11
                      Re: Speaker Cabinet Materials: Beyond MDF

                      I prefer baltic birch to MDF in almost everuy situation - much easier to work with and you can leave it plain finish if need be so lot less work in the end. Usually even cheaper than MDF if you plan on veneering the MDF. With birch you have an already-veneered surface so no extra cost there. Using a hybrid box of MDF and birch ply is also a good idea. Use 3/4" MDF as an internal liner, then build a 1/2" baltic birch ply shell over it. Saves some money on the thinner sheet of birch and you get a lot of added mass from the MDF.

                      One of my other favorite materials is clear acrylic plexiglas. REALLY dense stuff and quite stiff, plus it's clear so it's a different look. You can also get it in various colors including black. Downside is you need a special set of blades to use with it or it can crack or chip. Just a reference for the mechanical strength, 1-1/8" acrylic will stop a .45 slug dead, and is what they use in banks for the teller windows Reasonably priced considering the strength, but I can't consider it cheap, and I wouldn't build an entire box from it unless you want to spend a few hundred bucks - it's better suited for baffles.

                      I have also thought about doing a hybrid trans-lam style construction, where you cut a few of the ribs and make a "skeleton" of the box. Put a layer of glass cloth on the inside of the enclosure. Then in between the ribs you put a dense material like clay or something similar with good damping properties. Then put a layer of glass cloth over the outside, sand, then paint/polish. A guy made a clone of the B&W nautilus speakers this way:
                      http://www.frequencyblog.com/?p=101

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                      • #12
                        Re: Speaker Cabinet Materials: Beyond MDF

                        I did a mini version of the Magico mini with a corian baffle. i think that the cabinet was a positive contributor to the sound, that is, it did not contribute.
                        Attached Files

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                        • #13
                          Re: Speaker Cabinet Materials: Beyond MDF

                          Thick marble or granite... maybe just for the baffle though.

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                          • #14
                            Re: Speaker Cabinet Materials: Beyond MDF

                            Originally posted by lhwidget View Post
                            I've been intrigued by Vance Dickason's designs using 1/2 of a large sono-tube to form a 1/2 cylinder behind the drivers. He then fills the voids behind the sono-tube and the sides and back of the cabinet with dry sand.
                            Alternately, just use a half-sono and add a couple rib braces, as well as a top-bottom brace. I commissioned some cabinets from Nathan Funk along those lines to replace the big, ugly cabinets of my LCR Tannoy System 12 DMT II's, and they came out pretty well.



                            (Subwoofer in that picture is an M-Design Eleganza Bella 1200, which uses the Aura NS12-794-4A driver powered by a 500W plate amp.)



                            (Nathan's finish work is impeccable. The marks are dust and fingerprints.)

                            Tannoy's strategy with their DMT line cabinets was to use a hardwood "spaceframe" with MDF flat panels connected by flexible adhesive, and MDF bracing, including a brace that connects to the back of the drive unit with a piece of Poster-Tak like stuff between the brace and the back of the Dual Concentric's tweeter magnet. Those cabinets are the most dead commercial speakers I've seen, including Avalons, B&W Matrix and Nautilus lines, and even Tannoy's current TD-series home speakers. Something like that with flat panels of plastic or bamboo would likely look really cool. Use of solid pieces of hardwood for the spaceframe would allow really big roundovers, too. You could probably even buy large quarter-round pieces to make the job easier.

                            That said, cabinets seem no worse from the knuckle-test than the Tannoy ones did, and I can't hear any cabinet-related resonances that I know of. If anything, they're a little cleaner in the treble because of the huge roundovers on the baffle and lack of anything to cause diffraction.

                            Dr. Earl Geddes recommends constrained-layer baffles, MDF sides, and cross-linked oak dowels for bracing. I prefer birch, because it's prettier, but if one's concerned with sonics over the aesthetic possibilities that other materials may provide, that's probably the smartest way to go. For sound quality improvements, look to things like the largest possible radius roundovers you can do and other such improvements.
                            Last edited by DS-21; 12-06-2008, 04:17 PM.

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                            • #15
                              Re: Speaker Cabinet Materials: Beyond MDF

                              Originally posted by lunchmoney View Post
                              A friend of a friend made molds and poured concrete :eek:

                              Never saw them, but apparently they were amazing.
                              Nobody responded to this - I'm surprised. I have thought about this many times - in college, I was part of a team that would design, construct, and ultimately race a concrete canoe (Hey Ryan - you out there? :D). With the various additives that are available, it's pretty amazing what you can do with concrete.

                              ASCE Site here:
                              http://content.asce.org/conferences/nccc2008/index.html

                              Pics here: http://content.asce.org/conferences/...09/photos.html

                              I was thinking about this again in the past week. With a well designed mold, you could have virtually any shape - and very easily. Moreover, the effort goes into the mold - so if you wanted to make, say, 10 pair of speakers, the effort is GREATLY reduced.

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