Announcement

Collapse
No announcement yet.

Light cabinet construction techniques?

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

  • #16
    Sonotube.

    You will NOT get any enclosure lighter than if you use a sonotube construction. The cylindrical shape is ridiculously stiff by itself (I did finite element analysis just to prove it before I built my monstrous 2' diameter x 7' tall sonosub). No bracing needed with a sonotube (you can brace the endplate opposite the speaker side if desired). Wrap it with fabric or wood veneer, or any other desirable material, and you will have a very light weight, nice looking speaker.
    Statements: "They usually kill the desire to build anything else."

    Comment


    • #17
      Thanks for starting this thread! It's ridiculously enlightening.

      Comment


      • #18
        Originally posted by LIDAR View Post
        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.
        Interesting - do you recall the name of that product?

        --
        "Based on my library and laboratory research, I have concluded, as have others, that the best measures of speaker quality are frequency response and dispersion pattern. I have not found any credible research showing that most of the differences we hear among loudspeakers cannot be explained by examining these two variables." -Alvin Foster, 22 BAS Speaker 2 (May, 1999)

        Comment


        • #19
          Here're some pics of my foam filled, tile backer board build:

          https://pinkfishmedia.net/forum/thre....237894/page-3

          Comment


          • #20
            Might not be quite what the OP is looking for but here is a project I am working on. Using 2 x Peerless 6.5" HDS in a T-Line. 1.5" Styrofoam glued together with PL Premium. Plywood front for mounting.
            Attached Files

            Comment


            • #21
              Originally posted by Pallas View Post

              Interesting - do you recall the name of that product?
              Sorry, but I didn't see a name. They just sold these sheets of corrugated plastic to make custom sized pots. IIRC they were about the same price as regular nursery pots (so <$1 per gallon). I'll bet if you go to your local hydroponics or grow store they'll know what you are talking about if you ask for this.

              Comment


              • #22
                Originally posted by tom_b View Post
                My goal is to get to 125#, including the speaker.
                If you can't get it under 100lbs with plywood you're doing something very wrong. There is a catch22 with subs and weight though, if you make it too light it will move around on smooth surfaces when driven hard.
                Paul O

                Comment


                • #23
                  I've been building cabinets with 1/4" strips of Baltic birch installed in dados with cross braces to stiffen the box for some time.

                  This box has 1/2" sides with a 3/4" baffle

                  Click image for larger version

Name:	image_87880.jpg
Views:	154
Size:	745.4 KB
ID:	1454371

                  Same with this box. This was the bass section of my Cherry Pi entry that placed second in the open unlimited class at Midwest Audiofest in 2016. The system is very light with the use of 1/2" Baltic birch and neo drivers.

                  Click image for larger version  Name:	Cross Bracing.jpg Views:	0 Size:	812.5 KB ID:	1454373

                  Ron
                  C-Note Iron Driver Build
                  The Lydias
                  The Cherry π's
                  The Champs - Iron Driver 2015 Entry
                  My Projects Page

                  The good thing about science is that it's true whether or not you believe in it. - Neil deGrasse Tyson
                  http://www.youtube.com/watch?v=cjuGCJJUGsg

                  Comment


                  • djg
                    djg commented
                    Editing a comment
                    Stair treads, a mostly untapped resource.

                  • Dukk
                    Dukk commented
                    Editing a comment
                    quarter round would work as well. Both enclosures look great BTW

                  • tom_b
                    tom_b commented
                    Editing a comment
                    Brilliant. Love it. Thank you.

                • #24
                  Originally posted by Paul O View Post
                  If you can't get it under 100lbs with plywood you're doing something very wrong. There is a catch22 with subs and weight though, if you make it too light it will move around on smooth surfaces when driven hard.
                  I think a 1/2inch plywood box with decent bracing (like the pro-audio stuff billfitzmaurice mentioned) should weigh less than 50lbs for something as large as 8ft-cu. That drops below 40lbs if it's using cheaper fir plywood instead of the nicer voidless baltic. Also lighter if you'll be sticking toward a smaller size like the 5ft-cu mentioned in the first post.

                  Does stuff like that thick foam insulation have any advantages compared to decently braced 1/4inch plywood? I'd expect the plywood to be stiffer, less lossy/leaky, maybe a little easier to work with and a bit cheaper...and the thinner walls allow a slightly smaller outer dimension at the same internal volume.
                  I'd guess maybe the foam has a different resonant property that might allow it to get away with less bracing, but then it would still need the bracing to avoid flexing (or letting the whole box compress/expand)..so I'm curious but sceptical.
                  The water/weather resistance of the foam might be a cool positive in some situations, though the plywood could probably get similar results from being sealed/treated.
                  My first 2way build

                  Comment


                  • #25
                    Use of Baltic birch ply will be more rigid compared to construction grade.
                    Sono-tubes used to be popular. Round cardboard. The ultimate was concentric tubes with sand filling. I think spray foam might be a better update.
                    One could make their own structural panels, glue 3mm BB ply to either side of 1/2 inch rigid foam. Use a rigid glue like powered resin.
                    Just make it insane, but put on feet so you can get a hand truck under it.

                    If you go big, ya' gotta pay the price

                    Comment


                    • tom_b
                      tom_b commented
                      Editing a comment
                      Good ideas. Thank you.

                  • #26
                    I'm going to brainstorm some lightweight ideas for my next front 3 HT cjd Abouriou build. Fairly large MTMs with 2 hanging off my stairwell rail.

                    Comment


                    • #27
                      Originally posted by tvrgeek View Post
                      Use of Baltic birch ply will be more rigid compared to construction grade.
                      Sono-tubes used to be popular. Round cardboard. The ultimate was concentric tubes with sand filling. I think spray foam might be a better update.
                      One could make their own structural panels, glue 3mm BB ply to either side of 1/2 inch rigid foam. Use a rigid glue like powered resin.
                      Just make it insane, but put on feet so you can get a hand truck under it.

                      If you go big, ya' gotta pay the price
                      What would the 1/2inch of foam add/improve compared to simply gluing the 3mm BB ply sheets together (or using a 6mm sheet) and proper bracing to avoid noticeable resonance?
                      My first 2way build

                      Comment


                      • #28
                        ^ Spacing the wood veneers adds stiffness to the assembly. On something like an I beam, the top and bottom of the I provide the strength, the vertical web between them supplies the stiffness (basic explanation - structural engineers can stand down)

                        Comment


                        • #29
                          Lite ply is poplar plywood available in 1/8" and 1/4" thicknesses. 4'x8' sheets or smaller pieces. Not outrageously pricey. I found some 1/4" foam at Menards for under steel roofs, etc. A sandwich of lite ply and 1/4" foam would be extremely light. I would veneer as lite ply, in my model building experience, is not real hard surfaced.

                          I might try it.

                          At Menard's I found some 6mm (1/4") Baltic Birch veneered MDF. Really nice grain. This and foam 1/8" lite ply sandwich maybe.

                          Comment


                          • #30
                            Originally posted by Dukk View Post
                            ^ Spacing the wood veneers adds stiffness to the assembly. On something like an I beam, the top and bottom of the I provide the strength, the vertical web between them supplies the stiffness (basic explanation - structural engineers can stand down)
                            Does that spacing still work when the middle of the sandwich holding them together/apart is something somewhat flexible and spongy like that foam?

                            The I-beam analogy makes sense, but those are using a solid/sturdy material for the "I"'s neck to connect the top/bottom serifs which also adds rigidity along another axis both from the solid connection of two parallels and the shape (like trying to flex a knife along the cutting edge VS wiggling it side-to-side). The foam on the other hand would give a looser connection and a spongy/flabby shape more like a gel or an air gap between the layers instead of a rigid support...at least in my mental picture and inexperience. I think the foam only supports VS sliding the flat plains like a resistance when rubbing your hands together (at least for as long as the glue can hold the fragile foam sides from tearing), while not doing much against other directions of movement or flex.
                            The foam should offer more resonance deadening compared to a plain air-gap, but it should be possible to get a similar deadening (and equal or superior support) by gluing a few 1/2"x1/2"x1/2" wood blocks between the layers to connect and support the ply while fighting resonance. I think you'd need a solid/stiff connection between the layers for the two layers to get the rigidity benefit of spacing compared to a single layer...might need long+skinny strips or bridge style \I/I\I/I\ dowels connecting the layers rather than blocks to get the strongest effect.
                            Not sure, more just thinking aloud.
                            I'm feeling my knowledge gaps pretty hard right now, lol.

                            I should have some 1/4" ply and some foam insulation on-hand though. Maybe seeing/testing it in person will finally wrap my head around this thing.




                            Also just realized this sandwich would only realistically make sense if you're using really thin plywood...like 1/8".
                            If you're planning on using an outter and inner layer of 1/4" ply around a foam sandwich, that would already weigh about the same as simply using a single layer of 1/2"...which is already sturdy enough for touring musicians as a single layer without any added complexity.
                            My first 2way build

                            Comment

                            Working...
                            X