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Second attempt at bass traps.

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  • Second attempt at bass traps.

    My intention is to put one of these in each corner, with a helmholtz on top.

    I need to stretch the fabric next time.

    An apostrophe with an "s" does not mean plural.

    Speaker's IS NOT PLURAL.

  • #2
    Re: Second attempt at bass traps.

    Nice, any pictures of the backside?

    Comment


    • #3
      Re: Second attempt at bass traps.

      +1. More pics, more info please....

      What makes it a bass trap? How does it work?

      Comment


      • #4
        Re: Second attempt at bass traps.

        Originally posted by icor1031 View Post
        My intention is to put one of these in each corner, with a helmholtz on top.
        Have you run through the calculations for axial, tangential and oblique modes and determined there is an issue with coincident modes? Please share with us your thoughts and analysis. I'm sure there are many people out there contemplating the same thing for their troublesome rooms.

        What frequency are you going to tune the Helmholtz resonators to? (And how did you choose that Frequency?)

        Do you have a design sketched up? This is good stuff! Please share your ideas and designs. Thanks.
        ~Marty

        Baby Eidolons
        Sapphos
        Cables (Post #54)
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        • #5
          Re: Second attempt at bass traps.

          Originally posted by chrisn View Post
          Nice, any pictures of the backside?
          The back side is open, to make use of the air space in the corner. (That lowers the frequency the trap is effective to.) It has heavy fabric on the back side, and I can get a picture if you want.




          Originally posted by generic View Post
          +1. More pics, more info please....

          What makes it a bass trap? How does it work?
          It is filled with 4", 4lb mineral wool. See my reply to Chris, and the calculator below.
          An apostrophe with an "s" does not mean plural.

          Speaker's IS NOT PLURAL.

          Comment


          • #6
            Re: Second attempt at bass traps.

            Originally posted by ReissM View Post
            Have you run through the calculations for axial, tangential and oblique modes and determined there is an issue with coincident modes? Please share with us your thoughts and analysis. I'm sure there are many people out there contemplating the same thing for their troublesome rooms.

            What frequency are you going to tune the Helmholtz resonators to? (And how did you choose that Frequency?)

            Do you have a design sketched up? This is good stuff! Please share your ideas and designs. Thanks.

            The room calculator, and room measurements are useless for me. I am moving soon, so I am designing my traps to be wideband: I want them to be effective in any room, even though less effective in a specific room. If I have a major boost in my new room, I can build a narrow band helmholtz later.

            I wanted to use a 40Hz on the helmholtz, and I chose that because they are supposedly 80% effective to a full octave above and below their target Hz.. In other words: 40Hz target makes them effective to 20-80Hz.
            I have no idea how quickly they drop off after that.



            Please see here:
            http://www.mh-audio.nl/acalculators.asp#showcalc

            The graphs in the book show that at the tuning frequency the absorption is very close to 100%, but if we take 80% as being our goal, then it will do roughly one octave either side of the tuning frequency.
            ie, if we build a trap that is tuned to 50Hz, then we will get about 80% or more absorption between 25Hz and 100Hz.

            And for confirmation on the formula:

            http://www.gearslutz.com/board/bass-...alculator.html










            Also, the mineral wool traps play a role in my helmholtz target. I am not sure how to calculate the air space in the corner, but if took the mid point (it's 0" at the most shallow, and 12" at the deepest) of 6" and assumed a direct reflection back out, my mineral wool should get over .50 coefficient down to 80Hz. You can see, I am trying to overlap the helmholtz and this trap.

            If the sound wave also reflects in the corner, the effective air space should be increased above 6" (please correct me if that's wrong.)..

            I Assumed 17,000 flow resistivity, and used this:

            http://www.stanleyhallstudios.co.uk/...&s12=1&d12=150










            You asked about design.. I used 1x4s and made their inner diameter 23.5" x 47.125". The under-sizing is to compress the mineral wool, and prevent it from falling out.
            I attached moderately thick fabric with adhesive spray around the mineral wool, to keep the nasty fibers in.
            And then I used adhesive spray to attach the more attractive fabric.


            I suggest waiting until I finish building my dozen traps before following my design, in case I notice any errors. They should be done fairly soon; eight of them have a 3" air gap, and can hang on the wall. (I used 1x8s)



            Estimated results of my traps using 1x8s and going on the wall with a 3" air gap:

            http://www.stanleyhallstudios.co.uk/...0&s12=1&d12=76
            An apostrophe with an "s" does not mean plural.

            Speaker's IS NOT PLURAL.

            Comment


            • #7
              Re: Second attempt at bass traps.

              Hmm, I just noticed the dashed line (related to flow resistivity) on those charts. I should probably do a test soon, and see if they're at all useful down to 100Hz. If not, I might make more helmholtz designs.
              An apostrophe with an "s" does not mean plural.

              Speaker's IS NOT PLURAL.

              Comment


              • #8
                Re: Second attempt at bass traps.

                First tests:

                http://www.gearslutz.com/board/bass-...-any-good.html
                An apostrophe with an "s" does not mean plural.

                Speaker's IS NOT PLURAL.

                Comment


                • #9
                  Re: Second attempt at bass traps.

                  An apostrophe with an "s" does not mean plural.

                  Speaker's IS NOT PLURAL.

                  Comment


                  • #10
                    Re: Second attempt at bass traps.

                    Less wrinkly:

                    An apostrophe with an "s" does not mean plural.

                    Speaker's IS NOT PLURAL.

                    Comment


                    • #11
                      Re: Second attempt at bass traps.

                      That's nice looking. Have you heard or measured any affect to FR?

                      रेतुर्न तो थे स्रोत
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                      • #12
                        Re: Second attempt at bass traps.

                        Some.. I'll probably measure again when I get the other 6 built, and hung on the wall etc.

                        Originally posted by greywarden View Post
                        That's nice looking. Have you heard or measured any affect to FR?
                        An apostrophe with an "s" does not mean plural.

                        Speaker's IS NOT PLURAL.

                        Comment


                        • #13
                          Re: Second attempt at bass traps.

                          An apostrophe with an "s" does not mean plural.

                          Speaker's IS NOT PLURAL.

                          Comment


                          • #14
                            Re: Second attempt at bass traps.

                            Oh wow that's cool, how many are you going to make?

                            रेतुर्न तो थे स्रोत
                            return to the source
                            leviathan system thread
                            deadhorse thread
                            shockwave build thread

                            instagram :: greywarden_13

                            in war, victory . . . in peace, vigilance . . . in death, sacrifice.

                            Comment


                            • #15
                              Re: Second attempt at bass traps.

                              12, maybe 16.


                              I haven't found out how to eliminate the wrinkles. I did significantly reduce it on a few, though.
                              And I tried stretching the fabric inside of the frame, but it didn't turn out well.

                              Originally posted by greywarden View Post
                              Oh wow that's cool, how many are you going to make?
                              An apostrophe with an "s" does not mean plural.

                              Speaker's IS NOT PLURAL.

                              Comment

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