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The real world importance of cabinet bracing is?

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  • #46
    Neoprene gasket material is pretty cheap and can readily be found on, e.g. amazon.There's also silicon grade rubber gasket material that can also be found. Perhaps then, enclosure with gap, place silicon glue and then attach the rubber gasket material followed by more silicon glue and then the brace.




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    • #47
      I've heard Viton recommended in that sort of application. I don't know Viton differs from regular neoprene though. Sorbothane would be another possibility.
      ~Brandon

      Soma Sonus
      DriverVault

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      • #48
        Before I had completed my research suggesting that butyl rubber may be the most ideal rubber, I purchased some 1/16" thick, 1" wide neoprene strip for like $5 from www.rubbersheetwarehouse.com.

        Man, I couldn't find sorbothane for anything reasonable. Stuff is expensive!

        I'm in the process of building some cabs where the braces and chamber dividers will be affixed to the side panels using this neoprene strip glued between each using epoxy.
        I'm hesitant to use a friction connection. I feel like we need a rigid connection. Decoupling could actually prove beneficial, but that's not what I'm going for.

        I'll post some progress pics and thoughts as I work my way through it.

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        • #49
          Originally posted by civit View Post
          I'd recommend everyone read the paper on the LS50 linked earlier in this thread. The cabinet construction they recommend is easily achievable by DIYers with braces being affixed to interior walls with a layer of damping adhesive or butyl rubber between the brace and the wall. KEF provides a very clear illustration of this construction, with damping between the braces and the walls, and also between the braces and the driver magnet assembly.

          The compliant center of the port tube is another interesting development, and the measurements of midrange damping from port output are remarkable.

          I think xmax's construction method is a good way of doing it, but I think compliant magnet and baffle bracing would be an advantageous addition.
          Think of the outer box, an external extra layer that's damped and not "touching" the actual box.
          The reason I built them this way in the first place, Dan Auerbach wanted something
          that looked like an Altec monitor but compact with superior sound, it had to be extremely clean,
          accurate and LOUD. So in the process of achieving the goal it just seemed logical to have a box,
          in box (with another 3rd small box for the TB W6-1721) And in dealing with the inset drivers (Altec look)
          I was able to control diffraction with my foam "anti-wave" guides and "stealth cut" grill frame.
          Also having the grill is nice because people have no idea what they are listening to and
          don't get messed up with preconceived notions of what drivers they like and don't.

          I'm pretty sure a lot of people thought they used a ribbon tweeter for whatever reason.
          the little SB tweeters competes with the best in my book, when properly implemented.
          If you notice the power handling spec of most SB and a lot of Scan-Speak tweeters
          are derived using a 2nd order filter around 2600hz and they tend to really work well
          crossed in that area. This design uses a 2nd order medium Q passive XO
          on the mid and tweet. In the rear is a RSS26HF actively crossed over generally @ 120hz
          with the polarity reversed.

          Finally the package is power by 1 Nc122 and Nc502 Hypex Ncore amps
          I have quite a few pairs out there, especially in Nashville, if anybody
          would like to have a listen PM me.

          I have also got similar results mounting a ring under the drivers that is only
          screwed to the inner box for a more conventional look. (the "ring" is like a
          spacer preventing the driver from touching the outer box)




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          Attached Files
          Guess xmax's age.

          My guess: 15. His grammar is passable. His trolling is good.

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          • #50
            This design uses a ring under the Satori mid and tweet to mount them to the inner box plus Satori has it's own decoupling system.
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            Guess xmax's age.

            My guess: 15. His grammar is passable. His trolling is good.

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            • #51
              Bracing is important, but complex B&W-style bracing is a waste of time as most enclosure resonances are below the threshold of audibility (per Toole & Olive resonance study). Here is the Salon 2's bracing structure, and a study on cabinet resonance.
              Attached Files

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              • #52
                Originally posted by xmax View Post

                Think of the outer box, an external extra layer that's damped and not "touching" the actual box.
                The reason I built them this way in the first place, Dan Auerbach wanted something
                that looked like an Altec monitor but compact with superior sound, it had to be extremely clean,
                accurate and LOUD.
                xmax, I love the look of these little monitors. My question remains though - do you have bracing in the inner box?

                I'm going to be building some 8" 3 ways with leftover rs225s, and doing boxes like this might be a good option. I'm going to look into compliant bracing methods for the larger drivers and compliant gaskets for all the drivers.

                What I like about the LS50 damping is that it appears to work well, but the box is otherwise totally conventional. One big cross brace, that's it, just mdf and rubber.

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                • #53
                  Originally posted by civit View Post

                  xmax, I love the look of these little monitors. My question remains though - do you have bracing in the inner box?

                  I'm going to be building some 8" 3 ways with leftover rs225s, and doing boxes like this might be a good option. I'm going to look into compliant bracing methods for the larger drivers and compliant gaskets for all the drivers.

                  What I like about the LS50 damping is that it appears to work well, but the box is otherwise totally conventional. One big cross brace, that's it, just mdf and rubber.
                  In the mentioned little monitor there is NO bracing, after extensive listening and measurements we felt the 1 5/8" thick cab
                  being relatively small performed best with no bracing. Since the 6.5" woofer is in it's own box not touching the the bigger
                  inner/outer box, midrange coloration is nonexistent. Any flex the sub puts on the main enclosure is below 120hz
                  and minimal, if anything the construction softens the "Q" of the sealed box to help eliminate any "pokey" bass.
                  In my room they are like +/-2 from 28hz to 18khz and sure are fun!
                  Guess xmax's age.

                  My guess: 15. His grammar is passable. His trolling is good.

                  Comment


                  • #54
                    Originally posted by Squidspeak View Post

                    Kerry, did you use the green glue to laminate the panels together and then fabricate the cabinets?
                    No, Green Glue doesn't dry hard enough to hold things together. It's normally meant for sheet rock to prevent sound transmission through walls and you affix the first panel, Green Glue, and then screw the second panel over the top. Based on the company's info, screwing it down in the normal spacing of screws will compress the layer to the right thickness for transmission losses. I did the same thing with the outer panels. They are screwed to the inner. It definitely seems to work better on the larger side panels than the back panel and I'm assuming that is because of the screw spacing I had to use on the narrower back panel.
                    -Kerry

                    www.pursuitofperfectsound.com

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                    • #55
                      Originally posted by Navy Guy View Post

                      No, Green Glue doesn't dry hard enough to hold things together. It's normally meant for sheet rock to prevent sound transmission through walls and you affix the first panel, Green Glue, and then screw the second panel over the top. Based on the company's info, screwing it down in the normal spacing of screws will compress the layer to the right thickness for transmission losses. I did the same thing with the outer panels. They are screwed to the inner. It definitely seems to work better on the larger side panels than the back panel and I'm assuming that is because of the screw spacing I had to use on the narrower back panel.
                      We also use the green stuff for more critical applications but it's spendy! 100% silicone works pretty darn good,
                      we use 1/4" foam weather stripping to hold the 2 boxes in place while the silicone cures (stinky).

                      https://acousticalsolutions.com/prod...4aAlcLEALw_wcB
                      Guess xmax's age.

                      My guess: 15. His grammar is passable. His trolling is good.

                      Comment


                      • #56
                        This is something I read about (described by Earl Geddes, I believe), a way to do cross-bracing with constrained layer damping in a manner to get lots of shear in the dissipative layer. I haven't tried it. but it seems like a promising technique.

                        But on a related note, some years ago I made a bunch of boxes for an array of 8" bass/mid drivers, and the boxes sounded really boxy. The guy who made the boxes for me forgot about the internal bracing I asked him to do! I was playing with measurement setups and accelerometers at the time, so thought it would be a great opportunity for a Speaker Builder article. I measured the vibrations at several points on the baffle, then added a single front-to-back cross brace. It made absolutely NO measurable difference in that setup! Even with the accelerometer right where the brace was placed. When I installed shelf braces (that attached to baffle and side walls, with difficulty, then there was a visible difference in the graphs, though. This was only one instance, of course, and cabinet vibration isn't the same as radiated sound... but ever since then, I never do braces that don't couple to several different axes at least.

                        A fifth way to possibly reduce cabinet vibrations is to use waveguide/horn loaded drivers. Mechanically induced vibrations happen from mass of cones and voice coils getting shaken around, and it takes less of that to make the same sound level if the driver is coupled more efficiently to air.
                        Free & Free-form simulator/designer for Passive Crossovers
                        SynergyCalc 5: design spreadsheet for Wooden horns and DIY Synergy Waveguides
                        Super easy and cheap to make high performance sound diffusers

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                        • #57
                          Originally posted by bwaslo View Post
                          This is something I read about (described by Earl Geddes, I believe), a way to do cross-bracing with constrained layer damping in a manner to get lots of shear in the dissipative layer. I haven't tried it. but it seems like a promising technique.

                          But on a related note, some years ago I made a bunch of boxes for an array of 8" bass/mid drivers, and the boxes sounded really boxy. The guy who made the boxes for me forgot about the internal bracing I asked him to do! I was playing with measurement setups and accelerometers at the time, so thought it would be a great opportunity for a Speaker Builder article. I measured the vibrations at several points on the baffle, then added a single front-to-back cross brace. It made absolutely NO measurable difference in that setup! Even with the accelerometer right where the brace was placed. When I installed shelf braces (that attached to baffle and side walls, with difficulty, then there was a visible difference in the graphs, though. This was only one instance, of course, and cabinet vibration isn't the same as radiated sound... but ever since then, I never do braces that don't couple to several different axes at least.

                          A fifth way to possibly reduce cabinet vibrations is to use waveguide/horn loaded drivers. Mechanically induced vibrations happen from mass of cones and voice coils getting shaken around, and it takes less of that to make the same sound level if the driver is coupled more efficiently to air.
                          I also see you (correctly) did NOT center the brace top to bottom, in theory a centered
                          brace could create a harmonic resonance in the upper and lower halves
                          of the cabinet, (picture muting a guitar/bass string at the 12th fret).
                          Guess xmax's age.

                          My guess: 15. His grammar is passable. His trolling is good.

                          Comment


                          • #58
                            Automotive grade silicone gasket maker ?
                            They come in several different grades, qualities and quantities. Some remain very soft and elastic after curing. Which is needed to confirm to differing materiel expansions rates.

                            https://paceperformance.com/images/M98390068.tiff
                            http://www.dealers-mopar.com/chemica...082860_420.jpg
                            http://www.dealers-mopar.com/chemica...010884_420.jpg

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                            • #59
                              Over the past couple days I've had some time to work on my cabinets where I was trying to attach the braces and dividers to the side walls using a strip of neoprene rubber between them to damp the panel.

                              The rubber I was using was 1/16" neoprene strip and JB weld, 2 part epoxy. The neoprene is jet black in the picture and is just a little wider than the 0.75" panels. This is the main divider between the woofer chamber and the mid range chamber.

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                              I thought everything looked good. I got the strips aligned and clamped and waited for them to set over night.

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                              Well.... complete failure!
                              I guess the surface prep wasn't good enough, or I didn't rough up the neoprene, or something because I only got one pad to actually adhere properly. Most peeled back like the picture below. The neoprene is still very smooth and the wood panel is just sealed along the end-grain with epoxy now:

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                              Here is the only one that actually looked like it worked properly because I couldn't peel off the rubber:

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                              So reading up on the internet, it sounds like epoxy might work but I really need to clean the surface of the neoprene with a solvent and then rough it up considerably. Plus, the 5 min set time of the JB weld was a little quick and maybe hindered a proper set up?

                              I also read some forums that recommended Bostik 2402 or Dunlop S2000 specifically for bonding neoprene to wood.

                              Anyone around here have experience properly bonding rubbers to woods?


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                              • #60
                                From a practical standpoint I like to glue one side of the brace then caulk the other end before gluing on the opposite box side. The caulk could be replaced with a neoprene gasket similar to what you are attempting.
                                John H

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

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