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  • Aperiodic Membrane Location

    I have read a significant amount of posts and technical literature regarding aperiodic membranes. Most literature and diagrams show that the membrane is installed opposite the front baffle where the speaker is mounted. Can it be installed elsewhere on the enclosure? What if it was installed on the front baffle, below or above the subwoofer? Thank you!

  • #2
    I believe that in the old days (very old days) Dynaco or possibly Advent had a range of products (A10?, A25?, A35?) with enclosures named aperiodic. I am not sure if the enclosures used a membrane or a stuffed port, but I believe that they were on the fronts of the enclosures. Scanspeak sells a 290001 aperiodic vent and claims that it makes a sealed enclosure appear to be 20% larger. The "M" company sells it for $23.80 and has the Scanspeak recommendations. Jeff Bagby has a design named the Tributes with a series cross over in a tribute to Fried which uses a ported and highly stuffed enclosure with the port on the rear. I would suspect that the placement wouldn't matter as long as it isn't too close to a wall of the enclosure or the air flow restricted in any way. The experts on this forum have much more knowledge and experience.

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    • #3
      Google “dynaco a25 enclosure”

      http://diyaudioprojects.com/Technical/Aperiodic/

      I like to put them on the top with small speakers. I am a big fan of aperiodic enclosure even when the bass is over damped. They and TL loading just have the most natural sound bass to me.

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      • #4
        The old Dynacos I saw had the vent on the front bottom, a sort of shelf port but very firmly stuffed with fiberglass. Nice sounding speakers.
        Francis

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        • #5
          The response from an AP vent emits in a cardioid, and its tuning is more broadband than a standard Helmholtz port. The theory is that cancellation can occur if on the same face as the active driver, and rear placement negates this possibility a bit.
          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

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          • #6
            I've done a couple of aperiodic enclosure designs. Always on the rear of the enclosures and always with woofers in 3 way or 2 way designs. Never done an aperiodic subwoofer.
            Craig

            The lowest possible F3 box alignment is not always the best alignment.

            Designing and building speaker projects are like playing with adult Lego Blocks for me.

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            • #7
              Thank you for these excellent posts.
              Jeff Bagby has developed some software that apparently helps to model aperiodic subwoofer enclosures.

              I am using a Scan-Speak car audio subwoofer in a car audio application.
              http://www.scan-speak.dk/datasheet/pdf/30w-4558t06.pdf

              I am planning on 1.3 Cubic Foot enclosure and using an aperiodic membrane. Does this look right?

              I bought a Dynaudio Variovent, a Scan Speak Aperiodic Membrane, and materials to build my own that will allow me to manipulate the fill material.

              I thibk a single membrane will be fine for a ~12 inch subwoofer.

              Aince the subwoofer is upward firing, I plan to install the vent on the base of the enclosure as the back wall, opposite the front baffle, will be on the floor of the trunk/cargo area.

              Thank you for any further thoughts and ideas.

              It seems to me that aperiodic membranes have not been fully exploited.

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              • #8
                Basically set your Ql to 3.0, and model your box in your car as if your car interior cabin was part of the enclosure, ie a bandpass setup.

                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
                  Just out of curiosity, and while we're on the subject: I have a question. Even with the vent being so lossy, significant sound still comes out of the port?
                  Francis

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