Announcement

Collapse
No announcement yet.

Cabinet stiffening. . .

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

  • #46
    Originally posted by andy19191 View Post
    If you want to stop it moving place something heavy on top to...
    And that's the bit I'm getting to right there - if one were able to determine exactly how much weight to add with a mathematical model.

    I guess there are so many other variables (vibration, pressure, friction etc etc) perhaps there's little practical point to it?

    But I look at it like this.....if I were to bolt my woofer basket into a granite cliff face, I'm fairly certain the force exerted by the woofers motor only has one place to go - cone to air - nothing would be lost pushing against the cliff (ignoring sub-atomic). Could this be meaningfully calculated. I.e. I want a tower speaker with two 12inch woofers and I want the maximum transfer of cone energy to air - what weight should my cabinet be?

    Maybe its just an ignorant thought process with how many other factors are at play? But I'm curious non-the-less.

    Comment


    • #47
      Originally posted by andy19191 View Post
      As this thread demonstrates people generally can't follow engineering reasoning without possessing the basic engineering knowledge on which the reasoning is based. I have been pondering for a while whether it is worth the considerable effort to supply the basic engineering knowledge in a digestable form for non-engineers along with the engineering reasoning...
      Well....speaking for myself, yes please, I think it would be worth it. But its up to you. I cant speak for the individual encounters you've had with others but, realistically, the only difference between myself, a non-engineer in thiscontext, and an actual engineer in this context, is simply what we have been formally educated in. A non-engineer as defined here is no less intelligent, or unable to learn or comprehend...so please, don't tar us all with the same brush!

      Ultimately...a brand name speaker company is still err....."doing it themselves"

      Comment


      • #48
        I assumed damping "softened"/absorbed cabinet resonance, while bracing raised the resonance frequency/ies (and likely shortened resonance time-lengths and increased the amount of force needed to excite resonances via stiffening) and I'm guessing some of the less rigid forms of bracing might also offer some damping by linking panels with different resonant frequencies?

        Are there realistic amounts of bracing (distance between braced points, depending on the wall thickness and material) where it will either raise the resonances above ~20Khz, or shorten their time-length beyond a noticeable point, or increase the force needed to excite the resonance/s to something unlikely for a household speaker to output?
        Are these even the right questions (aside from adding strength) when it comes to bracing, and are there any missing important questions?

        EDIT: Reading the thread (instead of skimming) I'm realizing a lot of this has already been answered at least to some degree.
        My first 2way build

        Comment


        • billfitzmaurice
          billfitzmaurice commented
          Editing a comment
          Resonance here is a red herring. The assumption has been made by some that since the higher resonance that bracing gives accompanies lower coloration ergo coloration is reduced by dint of higher resonance. One very large fly in that ointment is that the use of very high mass, like concrete enclosures and sand filled panels, and constrained layer construction, all result in lower resonance, yet they still reduce coloration. In a similar vein the computer sims of how enclosures may flex might be reasonably accurate if you loaded an 18" long throw sub into an enclosure made of light gauge sheet metal. In the real world using real world construction methods and materials you don't get those results.

      • #49
        One thing ignored so far in this discussion is that even if a brace simply pushed resonances higher, materials such as wood tend to dissipate more as frequency rises.
        Francis

        Comment


        • #50
          Originally posted by billfitzmaurice View Post
          Resonance here is a red herring. The assumption has been made by some that since the higher resonance that bracing gives accompanies lower coloration ergo coloration is reduced by dint of higher resonance. One very large fly in that ointment is that the use of very high mass, like concrete enclosures and sand filled panels, and constrained layer construction, all result in lower resonance, yet they still reduce coloration. In a similar vein the computer sims of how enclosures may flex might be reasonably accurate if you loaded an 18" long throw sub into an enclosure made of light gauge sheet metal. In the real world using real world construction methods and materials you don't get those results.
          I wouldn't think moving the resonance higher or lower would inherently lessen coloration (except maybe in situations where it can be moved out of the drivers' passband), but I assume most bracing offers SOME level of natural damping via imperfections(I imagine it kind of like making the whole box a really large and non-ideal constrained layer instead of its walls). EDIT: and the above post mentions wood typically dissipates more as frequency rises...though I'm also guessing the ear is more sensitive to shorter and shorter resonances as frequency increases?

          And I assume the added stiffness brought by bracing makes some mid/low resonances more difficult without making higher resonances much easier/louder. It kind of looked like the tests shown earlier (braced VS unbraced) showed the bracing both increasing the frequency (a little) and damped some low/mid-frequency resonance.
          My first 2way build

          Comment


          • #51
            Simply put - Stop the exterior surfaces of the speaker cabinet from vibrating audibly into the listening environment.

            This ^ is what we are after.

            EVERYTHING else is just BS.

            Comment


            • LOUT
              LOUT commented
              Editing a comment
              Makes sense.

              Are many different methods (bracing, constraining/sandwhich-walls, adding damping materials or mass, etc.) all pretty good at that task, or is there one or two methods that are overwhelmingly better at the job without being prohibitively expensive nor crazy difficult?
              For subwoofer?
              For mids?
              Is tweeter ever really a concern for cabinet resonance (I'm guessing their low mass means "no")?

            • Steve Lee
              Steve Lee commented
              Editing a comment
              Lout,

              I cannot possibly answer your questions because I cannot control your listening environment nor listen within it through your ears or financial/WAF issues.

              For me - I have several listening rooms - none of them sound the same and each have their own positives and negatives and the speakers in each of them are all mounted differently and of different designs.

              Some audio sounds fantastic in some rooms and not so good in others but each of them sound great with certain audio played at certain levels.

              Cabinet vibrations transmitted to the floor don't really bother me as they add to the Bass.

              Sitting on a wall mounted shelf or a desk top they produce unwanted room resonances.

              This is why I put all my speakers upon at least 1/2" thick closed cell foam if they are small/light and upwards of 4" thick open cell foam as they get larger/heavier.

              I find that I want to excite the air with the speaker's sound and not the structure they are in.

              If the cabinet is stiff and you cannot feel the bass being emitted from the cabinets walls very much by placing your palm on them then this is going to sound good and tight to the ear - if the cabinet wall is flexing such that your palm is really feeling the bass, you have work to do on the cabinet either internally or externally.

              The Samba cabinets are mounted in the drum console on 1/4" closed cell foam and held into place on a shelf which surrounds the cabinet on all four sides (nested in an exterior box) made from Pine 2 X 10 lumber - this adds damping externally. I did install a window pane brace inside those cabinets but found that they still had significant bass vibration/emission from the side walls on the woofer axis - which is why I made the bracing differently on my new test cabinets - (3/4" MDF isn't very stiff - even over an 8" unbraced-span near a 6" woofer at moderate volume).

              The room they are in is dead/non-reflective - perfect for drumming.

              The drum mixes sound really good there on those speakers and sound like poo on all my other systems - I gave up trying to mix for everyone else and just started playing my drums to get better at them again instead of chasing my audio *** rather than getting better at nothing at all.

              Plus I spend more time in the shop now building new designs . . .

              Sorry for the wall of text up there ^ I could write a white paper but then I would have to argue/defend it later when I could be enjoying my life/hobbies instead . . .

              :D

              Later man and thanks for your feedback/inquiries - keep going!


              Steve.
              Last edited by Steve Lee; 07-31-2021, 05:53 AM. Reason: context correction

          • #52
            Response added at Post 51.2 above ^

            Comment


            • #53
              How I braced my subwoofer cabinet. All 3/4 mdf, double layer laminate baffle, and doubled on one other larger unsupported section. Plenty of fiberglass stuffing. The port is divided in half longitudinally by more bracing. Zero resonance that I could detect. 12" Dayton reference HF sub. This turned out to be a terrible subwoofer for my car because of it's low tuning and cabin gain. Was devastating between 20 and 30 hz. Too bad most music doesn't have content that low. Live and learn. On the plus side, that kicked of my interest in acoustics trying to figure out what the problem was.

              Comment


              • #54
                Very nice work, Sir!

                Comment


                • #55
                  Originally posted by Steve Lee View Post
                  I am an idiot - does that make you feel better?

                  Now, take your perceived superiority and go away . . .

                  Best wishes,

                  Steve.
                  It is easy to get carried away when you are dealing with anonymous user names but you still need to be open minded to other opinions. I have a sneaky suspicion that andy19191 may not just be a regular diy contributer.

                  Comment


                  • #56
                    Originally posted by davidroberts View Post

                    It is easy to get carried away when you are dealing with anonymous user names but you still need to be open minded to other opinions. I have a sneaky suspicion that andy19191 may not just be a regular diy contributer.
                    Admittedly, I became frustrated as did others with the delivery of his message [whatever it was] and it may be due to a cultural/social difference/misunderstanding.

                    However, he had not offered any empirical data/guidance that would assist us who are actually building speaker enclosures/did not demonstrate his experience/message so it was not possible to actually take from his discourse any useful information while being chided for lacking intelligence equal to his apparent education.

                    Experience is the best way to learn - show us how to learn what you know and and we will follow . . .

                    Thanks for the reality check and 1919 - please try again to get you message across.

                    Best wishes and PTL, guys . . .

                    Steve.

                    Comment

                  Working...
                  X