Announcement

Collapse
No announcement yet.

Speaker Cabinet Materials: Beyond MDF

Collapse
X
 
  • Filter
  • Time
  • Show
Clear All
new posts

  • #31
    Re: Speaker Cabinet Materials: Beyond MDF

    Originally posted by audionut71 View Post
    Bob or Max,
    I came across a deal on CL last year to get 2 sheets of 1-1/4" ex-gas station attendant protector, but I have no idea what material it is. Is there an easy way to find out? I have heard that the two differing materials (polycarbonate or acrylic) require differing methods of cutting or machining, is this correct?

    I'd love to make a sub enclosure out of this stuff! Except that the box would weigh a TON!!!
    If I recall correctly, from the edge view, Lexan looks almost black while acrylic will be basically clear.

    Or you can just whack a corner with a hammer and see if it chips. No chip, it's likely Polycarbonate.

    On the machining question, You have to take it a little easier with with PC it is more difficult to cut and is rougher on the tools. You really don't want either one to heat up as you are cutting, that is important. Acrylic is really brittle so take it easy and get a feel for it. Sometimes it will just shatter and toss chunks at you. WEAR GLASSES!!! If you're Routing that thick stuff, make sure you secure it first. I realize it's heavy but things can get ugly very quickly. You will also want to cut it in 3-4 gradually deeper passes. If you divide it equally it should act the same each time. If you need to, afterward you can do a light full depth cut to clean up any stepping left in the edge. I like a bit with plenty of relief for the chips to escape. The Onsrud O-flute in 1-flute or 2-flute is excellent, available, and not obscenely expensive. Sawblades that are intended for cutting veneer work nicely on brittle plastics. Carbide tools are pretty much a must.

    bb
    Last edited by bobblickle; 12-08-2008, 12:24 PM. Reason: added machining content

    Since we cannot know all that there is to be known about anything, we ought to know a little about everything.
    - Blaise Pascal (1623 - 1662)

    Comment


    • #32
      Re: Speaker Cabinet Materials: Beyond MDF

      I know from my old job selling construction supplies that I will need a tablesaw blade with a high tooth count and "triple chip" teeth, but how in the world do I keep the cut cool? I understand the multiple passes w/ the router, i guess the same may have to be done w/ the saw. I am dreading starting this project, because I am sure that I will make some mistake and destroy the material.
      Proud creator of the Frojo, and many other ridiculously named speakers.

      Comment


      • #33
        Re: Speaker Cabinet Materials: Beyond MDF

        On the saw you just want to procede slowly and steadily but don't stop. It's really not much different than cutting Rock Maple or Hard Oak. Yes, of course you can take multiple depth passes with the saw too. You need to load the tool because the chip ejection is what cools it. Basically, cut as heavily and rapidly as you safely and comfortably can and do not stop.

        Do test cuts. Sacrifice an Inch out at the end to get a feel for it. Measure twice cut once :D You'll do fine. If you make a mistake, build a smaller project! Don't be surprised when it stinks, keep cutting!

        Do let us know how it goes

        bb

        Since we cannot know all that there is to be known about anything, we ought to know a little about everything.
        - Blaise Pascal (1623 - 1662)

        Comment


        • #34
          Re: Speaker Cabinet Materials: Beyond MDF

          Originally posted by daveh View Post
          Hey Phil. Where did you find those bamboo cylinders. I have been looking for something like that.

          DaveH
          Try kohls or home store. Target had the cut off pyramids. Both kohls and home store had the bamboo cylinders

          Comment


          • #35
            Re: Speaker Cabinet Materials: Beyond MDF

            There are two disadvantages to boxes. The first is the resonance of the box. Enough mass and/or bracing can reduce or eliminate that, but then there's the second problem, which is reflection back through the cone. You can stuff the box to reduce that, but you can't eliminate it completely at the low frequencies that would excite the box resonances. So you need to decide if going to all that effort to make the box ultra-stiff is worth it to only treat half the problem.
            "We’ve heard that a million monkeys at a million keyboards could produce the complete works of Shakespeare; now, thanks to the Internet, we know that is not true."
            –Robert Wilensky

            Comment


            • #36
              Re: Speaker Cabinet Materials: Beyond MDF

              Originally posted by audionut71 View Post
              I am dreading starting this project, because I am sure that I will make some mistake and destroy the material.
              No guts, no glory! Like Bob said, do a few tests on an edge to see if your method is going to work. If you can pull it off, you'll have a ridiculously dead sub box! Just make sure to put a driver in there that is worthy

              Comment


              • #37
                Re: Speaker Cabinet Materials: Beyond MDF

                May I ask, then, if plywood and MDF are preferred materials, any ideas for making them "better." I'm making a pair of 70l NatPs with three horizontal braces at 1/2, 1/3 and 1/5 points and I see a need for more, if only to connect the centers of the flat areas inbetween, plus top and bottom.

                Bracing addresses cabinet effects by damping low order modes but it seems to me that added panel mass will reduce cabinet contributions further by driving down resonant frequencies to those damped by the bracing.

                Any thoughts?

                I do have access to large quantities of ferrite beads and epoxy ....

                Have fun,
                Frank

                Comment


                • #38
                  Re: Speaker Cabinet Materials: Beyond MDF

                  at the risk of thread-jacking...

                  If i do get this 1-1/4" mystery bullet proof material cut and machined properly, what is the proper adhesive to assemble it with?

                  Just make sure to put a driver in there that is worthy
                  I think I have that covered... Stay tuned for a write up on my current sub. It uses a custom built 15" driver that I happen to have 2 of...bwahhhaaahhhh (evil laugh)
                  Proud creator of the Frojo, and many other ridiculously named speakers.

                  Comment


                  • #39
                    Re: Speaker Cabinet Materials: Beyond MDF

                    Well the great thing about acrylic/lexan/polycarbonate is that the glue to use is the same for all of them: http://www.eplastics.com/Plastic/Lex...carbonate_Glue

                    It's a solvent glue, so it actually chemically joins the two pieces together creating a very airtight and strong bond. You want the #40 "epoxy" type or the #16 "syrup" type and not the #3 thin liquid type because it's likely your edges will not be perfect and the thin glue will not be sufficient to bridge the gaps. The #40 is stronger but takes a lot longer to set and I think the #16 will be sufficient.

                    The #16 glue sets VERY fast, within five minutes.
                    The #40 glue sets in about an hour.

                    When you glue, use corner clamps, but don't over tighten them. You want to keep the glue inside the joint and not force it out, which will leave you with a big mess. Also don't use too much glue. It should be brushed on thin and just enough to cover the surface, not a thick bead like it's OK to do with wood glue. You have to remember that with plastic glue it's actually melting the plastic to itself, and the glue itself has no structural properties and almost completely evaporates during drying. I'd also run a bead along the interior edges to ensure an airtight seal.

                    Comment


                    • #40
                      Re: Speaker Cabinet Materials: Beyond MDF

                      Max, you rock!

                      Now I have to get off my a** and figure out how i'm going to do this.:eek:

                      I'll keep everyone updated!!

                      Stan, get over here NOW!!!!! I can't carry this stuff downstairs by myself!:D
                      Proud creator of the Frojo, and many other ridiculously named speakers.

                      Comment


                      • #41
                        Re: Speaker Cabinet Materials: Beyond MDF

                        pvc. See Calipso's below, using PVC pipes for the midranges.
                        The Calipso Line Array System: http://techtalk.parts-express.com/album.php?albumid=9

                        Comment


                        • #42
                          Re: Speaker Cabinet Materials: Beyond MDF

                          Having built quite a few boxes out of HDPE for the fabs at Motorola I can tell you that HDPE is not actually glued together, it's welded using a thermoplastic welder. The industry standard welder is made by a company called Seelye.http://www.seelyeinc-orl.com/index.html. Harbor Freight also sells a cheapie but it only comes with a tip for plastics like pvc.

                          http://www.harborfreight.com/cpi/cta...emnumber=41592

                          In addition to a set of several different expensive welding tips you of course need a good router or two and a fairly large air compressor that can keep up since your essentially have a large leak going when using the welder.

                          And the obligatory bottle of isopropyl alcohol to preclean your joints.

                          It takes alot of practice to gain the skill to weld plastic properly but using HDPE would make a great speaker box or even using translucent PVC. I've considered selling small 0.75 - 1.0 cf cabinets but they would be expensive to build with 3/4" to 1" material. They would however be water proof though.

                          Comment


                          • #43
                            http://www.woodcraft.com/family.aspx?familyid=3958

                            is very consistent but try gluing veneer to a phenolic face... So why go through the trouble when MDF works so well. "if it aint broke, don't fix it"
                            Mark


                            http://www.diy-ny.com

                            Comment


                            • #44
                              Re: Speaker Cabinet Materials: Beyond MDF

                              Has anyone ever considered concree backerboard or any of the similar heavy dense materials to back tile installations? I'd figure a couple of layers of that with a layer of damping in between would be quite effective.

                              Comment


                              • #45
                                Re: Speaker Cabinet Materials: Beyond MDF

                                concrete backerboard would work.

                                from the inside to the outside.

                                mdf/glue/rubber pond frabric/mastic/backer board/mastic/tiles

                                nice look. any tile you want even marble. just hard to cut a circle in the marble.

                                Comment

                                Working...
                                X