Announcement

Collapse
No announcement yet.

How ManyPoints of Contact for a Removable Baffle?

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

  • How ManyPoints of Contact for a Removable Baffle?

    With rear mounting the tweeter, I am going to make the baffle removable. My question is, how many points of contact to I need to make sure it is air tight in a 20l sealed cabinet. dimensions are 8.5"x18". Right now I have 8 (the green little dots). There is also a 1/4" dado around the edge and 1" thick baffle.
    Attached Files

  • #2
    What is the baffle made of? If it's stiff like baltic birch ply or a real hardwood I'd say your 8 mounting fasteners is fine. If it is MDF then maybe, maybe not.
    Craig

    Comment


    • #3
      Originally posted by PWR RYD View Post
      What is the baffle made of? If it's stiff like baltic birch ply or a real hardwood I'd say your 8 mounting fasteners is fine. If it is MDF then maybe, maybe not.
      It is mdf. The cabinet is BB ply. I will be using these to screw the baffle to:
      https://www.parts-express.com/10-32-...-pcs--081-1094

      Comment


      • #4
        Is it double? Are you using 2, or just 1 panel?

        With 2 you'll have a nice strong baffle and be able to use the inner in many ways to help secure it thoroughly, leaving the outer focused on the drivers, recesses and simply attaching to that.

        This is what I wound up doing in a total custom design I came up with after many iterations until I was happy. The results have been phenomenal so it seems worthy of mention as 1 of so many options.

        Using a single baffle would work fine too if it's not going to be supporting heavy loads and big pressure.

        Mine is overkill or an example of an extreme, but I love overkill. Has worked great so many times for me so it's habit.

        It has an edge dado 1/16 inset, a chamber dado in the center also 1/16 inset + a dowel, also 1/16 inset. It all fits like a puzzle which was a primary goal because once everything is honed and sanded a bit it automatically aligns itself perfectly every time, all the time, making back and forth assembly a breeze - another goal of my design.

        Some primary goals were outstanding strength, puzzle piece fitment and excellent seal. When I'm ready to leave it on for a while I'll add driver gasket around the inner baffle dado, creating about as tight a seal one can manage short of glue I believe.

        Here's a few shot, an old WIP and a SU of what actually exists now, I don't have shots of these aspects in situation available currently. The first is the backside of inner with edge dado. Outer baffle bolts to it etc.

        Click image for larger version  Name:	Dscf0276_cropped.png Views:	1 Size:	438.0 KB ID:	1390196
        Click image for larger version  Name:	DadoAndRodExample.png Views:	1 Size:	194.8 KB ID:	1390197
        Feel free to rip my assumptions apart when wrong, or fix if close.

        Passive Radiators:
        All PR(s) Vd must be at-least double all woofer(s) Vd. Calc = Sd x Xmax to get Vd for all PR(s) and all woofer(s). A combined PR(s) Vd equal or > than a combined woofer(s) Vd is usable.
        Woofer(s) with large Xmax vs Sd, all PR(s) with Xmax at-least double all woofer(s) Xmax is usable.
        A PR max weight is said to be its Mms x3

        PR Systems - tight focus with key parameters.
        PR Speaker Design - thorough coverage.

        Comment


        • #5
          Here are actual pics. I have a 1" tab on the sides. I can easily do 2 or 3 vertical. My thought was to use the internal bracing as another attachment point which would only allow for the additional two. If I drill directly in to top and bottom pieces, I can do as many as needed.
          Attached Files

          Comment


          • #6
            I use 8 on my MTMs. I like a recess for the gasket when possible. For a recessed panel, I try to get the panel flush with the gasket compressed. I use pointed wood screw type of fasteners, cap screw head, pocket screws, or black sheet metal screws.
            John H

            Synergy Horn, SLS-85, BMR-3L, Mini-TL, BR-2, Titan OB, B452, Udique, Vultus, Latus1, Seriatim, Aperivox,Pencil Tower

            Comment


            • #7
              Originally posted by Ironman129 View Post
              Here are actual pics. I have a 1" tab on the sides. I can easily do 2 or 3 vertical. My thought was to use the internal bracing as another attachment point which would only allow for the additional two. If I drill directly in to top and bottom pieces, I can do as many as needed.
              Now able to see how much meat (1") you've got behind the baffle to attach, there's a decent chance you'll be good to go with your original design with just a couple additions, unless the pressure is intense.

              What size are the drivers? 5" - 7"? With it being sealed and those in parallel it'll be moderate+ pressure pending how hard you drive that sucker.


              For screws I used SPAX #8 1-1/4" construction. Against a black satin face and in particular due to the absolute precise positioning of every screw hole based directly from CAD their silver head winds up looking cool, which is something I considered at the time but I wasn't sure if it actually would look good or not until complete. I have India Ink to dip the heads in so they'd disappear and that was the plan if they looked like crap afterward.

              However when I told the wife I was considering doing that she put an uproar saying how they actually add to the effect, mentioning on her own how perfect their spacing from each other is and in relation to the edges of everything it looked machine made. Hard to turn down a bonus out of the blue WAF!


              As I mentioned and jhollander, a strip of gasket material can do wonders and targets sealing as one of its purposes. That, plus my vote for going ahead with adding screws to the internal bracing for the baffle and it seems likely you'll be in good shape ready to boom. Does the baffle flush against the 4 bracing ends? It's hard to tell but looks like it might. If it does that's 4 not 2, unless there's something I can't see.

              Gasket referred to is
              Attaching to the internal bracing should provide 2 additional benefits at minimum. More secure helping the baffle seal, but it'll also tie the bracing better to the front baffle pushing panel resonance higher, ideally out of the drivers range pending what they'll actually be playing.

              It should do that via creating more rigidity (smaller panel sections) in the baffle itself. The smaller a section of panel the higher its resonant frequency goes because it can't flex as easily vs larger span of a panel section.

              jhollander or other experts can expound further or correct mistakes in my post if I've made some - it's been quite a time since I've had to consider this factor, which I had just learned at the time in the first place.

              It'll come back into focus for me once I do a new sub build though.

              Updated:
              That's a great build by the way. Looks cut and flushed extremely nicely and I love how beefy the bracing is, especially vs the size of the box, and their design. Definitely something to be proud of even though no one else will see it - you know it's there, and the sound improvements provided by the extra overall rigidity will too
              Last edited by Thump; 10-11-2018, 08:44 AM. Reason: Extra comment + typo + info
              Feel free to rip my assumptions apart when wrong, or fix if close.

              Passive Radiators:
              All PR(s) Vd must be at-least double all woofer(s) Vd. Calc = Sd x Xmax to get Vd for all PR(s) and all woofer(s). A combined PR(s) Vd equal or > than a combined woofer(s) Vd is usable.
              Woofer(s) with large Xmax vs Sd, all PR(s) with Xmax at-least double all woofer(s) Xmax is usable.
              A PR max weight is said to be its Mms x3

              PR Systems - tight focus with key parameters.
              PR Speaker Design - thorough coverage.

              Comment


              • #8
                I think you'll be fine with the 8 fasteners, as I'm seeing the baffle at 1.5" thick, correct? I used 4 in my Fenrir because that is what was in the baffles I used. I can see a smidge of flex at the midpoints, and the baffles are 1" thick. Since you have 1.5" thick MDF, the 8 fasteners ill be fine.

                I know you are using the hammer-in style, so that is likely 1/4-20 bolt territory. I like the furniture bolts with the large Allen-heads as this provides a larger surface area for holding tight, and they are what I used. I used the knife-style thread-in instead of the hammer-in types though. A bit of Gorilla Glue on the collar/neck will help them hold in place better.

                And now- whatcha building? What drivers? Did you finish the sub yet?

                Later,
                Wolf
                "Wolf, you shall now be known as "King of the Zip ties." -Pete00t
                "Wolf and speakers equivalent to Picasso and 'Blue'" -dantheman
                "He is a true ambassador for this forum and speaker DIY in general." -Ed Froste
                "We're all in this together, so keep your stick on the ice!" - Red Green aka Steve Smith

                *InDIYana event website*

                Photobucket pages:
                http://photobucket.com/Wolf-Speakers_and_more

                My blog/writeups/thoughts here at PE:
                http://techtalk.parts-express.com/blog.php?u=4102

                Comment


                • #9
                  I think that you'll be fine with the current planning. Like Wolf, I like connector bolts and brass threaded inserts. The connector bolt heads have a large surface area which is ideal for soft materials like MDF.

                  One thing that is nice about the black oxide connector bolts is that you can chuck them into a drill press, use a very fine grit sandpaper to remove the original black oxide finish down to polished bare metal. Then use gun blue to really dress them up.



                  Bill Schneider
                  -+-+-+-+-
                  www.afterness.com/audio

                  Comment


                  • #10
                    The only reason I have some reservations about MDF is it flexes pretty easily when it gets machined down to a less substantial cross sectional area (the area I have circled in red). This has happened to me. That area gets material removed from the front for the driver frame's rebate, and ideally material removed from the back to allow the driver to breathe. If you end up rounding over the top and bottom baffle edge it gets even more compromised. I've had the pressure from a very thin foam gasket literally bow the baffle out in that area. Hardwood and BB ply are stiff enough this hasn't been an issue.
                    Attached Files
                    Craig

                    Comment


                    • #11
                      If it's bowing out just thin down your gasket in that spot i.e. if the side is 3/4", there is no need for a 3/4" wide foam gasket. A 1/8" strip is plenty. It's just a speaker box, it doesn't need hold back much pressure.

                      Comment


                      • #12
                        Originally posted by TMM View Post
                        If it's bowing out just thin down your gasket in that spot i.e. if the side is 3/4", there is no need for a 3/4" wide foam gasket. A 1/8" strip is plenty. It's just a speaker box, it doesn't need hold back much pressure.
                        Exactly. I'll update my post as I didn't specify the gasket I was talking about, which is likely (or maybe) what jhollander was also referring to, but not certain.

                        Anyway, it's just this stuff: Part # 260-540


                        Originally posted by williamrschneider View Post
                        ...
                        One thing that is nice about the black oxide connector bolts is that you can chuck them into a drill press, use a very fine grit sandpaper to remove the original black oxide finish down to polished bare metal. Then use gun blue to really dress them up.
                        Those are fantastic. Will definitely keep that in mind and may wind up trying it out on my upcoming sub project. That just looks great, thanks for sharing it.

                        Feel free to rip my assumptions apart when wrong, or fix if close.

                        Passive Radiators:
                        All PR(s) Vd must be at-least double all woofer(s) Vd. Calc = Sd x Xmax to get Vd for all PR(s) and all woofer(s). A combined PR(s) Vd equal or > than a combined woofer(s) Vd is usable.
                        Woofer(s) with large Xmax vs Sd, all PR(s) with Xmax at-least double all woofer(s) Xmax is usable.
                        A PR max weight is said to be its Mms x3

                        PR Systems - tight focus with key parameters.
                        PR Speaker Design - thorough coverage.

                        Comment


                        • #13
                          Originally posted by Wolf View Post
                          I think you'll be fine with the 8 fasteners, as I'm seeing the baffle at 1.5" thick, correct? I used 4 in my Fenrir because that is what was in the baffles I used. I can see a smidge of flex at the midpoints, and the baffles are 1" thick. Since you have 1.5" thick MDF, the 8 fasteners ill be fine.

                          I know you are using the hammer-in style, so that is likely 1/4-20 bolt territory. I like the furniture bolts with the large Allen-heads as this provides a larger surface area for holding tight, and they are what I used. I used the knife-style thread-in instead of the hammer-in types though. A bit of Gorilla Glue on the collar/neck will help them hold in place better.

                          And now- whatcha building? What drivers? Did you finish the sub yet?

                          Later,
                          Wolf
                          The baffle is 1" thick. Tweeter is the AST2560 and the woofer is the Satori MW16P. Pete is just finishing up the XO. I can use a hurricane nut on the sides, but if I am fastening to the top or internal bracing, I will nee to use the hammer in type.

                          Weird thing about the sub. I got the enclosure all built up and took a trip down to mexico, came back and the driver was gone. Only the driver. I also had a TC Epic 12, a bunch of power tools, nothing else disappeared. So now I am going to use the 12" with 2 of the RSS315.

                          Comment


                          • #14
                            Originally posted by williamrschneider View Post
                            I think that you'll be fine with the current planning. Like Wolf, I like connector bolts and brass threaded inserts. The connector bolt heads have a large surface area which is ideal for soft materials like MDF.

                            One thing that is nice about the black oxide connector bolts is that you can chuck them into a drill press, use a very fine grit sandpaper to remove the original black oxide finish down to polished bare metal. Then use gun blue to really dress them up.
                            I like the look of the connector bolts. I can have the CNC counter sink the head. I am a little worries that it might hit the waveguide, but I have a tester piece that I can try first. Thanks for all the help. Looking forward to this project coming together!!

                            Comment


                            • #15
                              Originally posted by Thump View Post

                              Exactly. I'll update my post as I didn't specify the gasket I was talking about, which is likely (or maybe) what jhollander was also referring to, but not certain.

                              Anyway, it's just this stuff: Part # 260-540
                              Definitely plan on using the speaker gasket.

                              Comment

                              Working...
                              X