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135hz Semented Midbass Horn Build

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  • 135hz Semented Midbass Horn Build

    I have decided recently to build a full horn speaker pair, likely 3 or 4 way. As of current I have a pair of Seos24 horns to play with and I'll be using those with the Radian 1.4" 745PB CD, I will test this combo in the 600-18khz range initially to see how it sounds and how flat I can EQ it. If I don't like the top end then I may add a CD or other tweeter above it, but more on that later.

    What a beast!



    I am also considering building some 18" JBL 40hz horns as well for the bottom end, we'll see.

    I got some plans from John Inlow (he's been really great to work with!) for a 135hz horn that uses the B&C 12" 12PE32 midbass, I had to wrap my brain about how to build this thing and finally found a way to do it that I was comfortable with. Note a 12" compound sliding miter saw is a huge help. Since this is the first segmented horn I've built, I decided to build one prototype just to test some of my build techniques and also to see how it sounds and what the FR looks like. Again I only built one and this is by no means a final build, based on what I learned on this one I will be building 2 more with changes his weekend.

    First I started with the compression chamber, the driver sits in about 1-2 liters of airspace, crazy I know! I started by ripping a piece of 5.5" wide stock with a 22degree angle on each side, basically a parallelogram. Then this piece goes in the chop saw, miter set to 22.5 degrees, I found if I can prop this piece up on the 22d angle then I can make the 22.5d cut and it automatically sets up the compound angle as well, which is around 43d





    By setting up a stop you ensure each piece is identically long, just flip the piece top to bottom with each cut and you only need 8. I can literally build an octagonal box up to 5.5" tall in a matter of minutes now. I thought about how the hell to clamp these things and then I wondered if I could just tape them together...wala!











    Unfolded, just run a bead of glue down each crotch face, wrap it up and tape. I put a flat board on top with some weight on it on a flat surface just to keep it totally square. Using the miter saw its easy to cut the top "cap piece" out as well. I also did a flat octagonal flange which I glued to the bottom of the chamber as a mounting flange. Now for the fun part, the actual horn! This is what I did on this first piece below, I will be making my final horns using a different technique (similar result) that is faster, easier and gives a little nicer result.

    Basically I'll make sections with the miter saw using the compound angle feature, since the saw can cut up to 13" wide I can just build each horn in segments. First I traced out my sections and rough cut oversized versions. Then I made a template with some 1/2" plywood, I used this template to router flush cut each piece so they are all identical. Identical pieces are the key to making these horns!

    Bottom flare



    Top flare



    Flush cutting the pieces





    Then since I had already cut the primary angle, I just needed to cut the compound angle which I did with the table saw, about 41d for the lower flare and 43 for the upper





    And boom!







    I'm skipping a few steps but here is basically where things ended up















    Hornresp modeled response



    Actual response, not bad!



    I am still breaking it in but wow is this efficient! Midbass is very fast and impactful like nothing I've ever heard, for fun I temporarily threw a DE250 and Seos12 in the mix and threw a 6db cap on it, not too bad! This is definitely a very lovable setup even w/o a sub, granted this is all hair left channel listening so far =)



    More to come soon, let me know your thoughts and if you have any questions!

    Thanks,
    Javad
    --
    Javad Shadzi
    Bay Area, CA

    2-Channel Stereo system in the works with Adcom components and 4-way towers

  • #2
    Very cool, nice wood work!
    A mains
    The Ventures
    Open Invit8tions
    RSR
    Sound Troopers
    Acorns
    442
    DGBG's
    The Monuments

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    • #3
      https://www.youtube.com/watch?v=dhJ-7KIf6k8
      craigk

      " Voicing is often the term used for band aids to cover for initial design/planning errors " - Pallas

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      • #4
        Thanks 6thplanet and hah craigk !
        --
        Javad Shadzi
        Bay Area, CA

        2-Channel Stereo system in the works with Adcom components and 4-way towers

        Comment


        • #5
          ​WTF is that? Did you accidentally post the wrong link or am I totally missing the supposed connection?

          Comment


          • #6
            Originally posted by View Post

            ​WTF is that? Did you accidentally post the wrong link or am I totally missing the supposed connection?
            "Feeling horn-ey, get it?
            --
            Javad Shadzi
            Bay Area, CA

            2-Channel Stereo system in the works with Adcom components and 4-way towers

            Comment


            • #7
              Originally posted by JavadS View Post

              "Feeling horn-ey, get it?
              ​OK, I got it. I guess that I'm just a bit slow, either that or the crappy music really distracted me. Thanks for the clarification.

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              • #8
                Nice job! What is the width of the exit? How do you plan on finishing it? Looking forward to seeing the SEOS24 stacked on top.
                Originally posted by
                ​WTF is that? Did you accidentally post the wrong link or am I totally missing the supposed connection?
                You're too literal.
                "He who fights with monsters should look to it that he himself does not become a monster. And when you gaze long into an abyss the abyss also gazes into you." Friedrich Nietzsche

                http://www.diy-ny.com/

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                • #9
                  Very nice work
                  .

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                  • #10
                    Now that is something special. Can you say how you went about figuring the compound angles? I've thought about this before, but never tried to do it. I'm also assuming the various segments will join up, how well do the sizes match?

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                    • #11
                      Wow Javad, that is some piece of work.
                      Can you say more about how you calculated the compound angles? I have thought abut this before, thinking of using router bits for the angles, but got no farther than that; you are way ahead.
                      Also, the segments do need to join up I assume, how well are you able to match the sizes?

                      Comment


                      • #12
                        Originally posted by Face View Post
                        Nice job! What is the width of the exit? How do you plan on finishing it? Looking forward to seeing the SEOS24 stacked on top.
                        The ID of the outlet is about 20", the base of the throat is 3.7" This is just a prototype as discussed above, I think the final versions I'll be making with Maple veneered poplar plywood, and the exit of the horn will be solid poplar as will the driver chamber, considering using some black stain and keeping the solid poplar natural, then I'd extend this theme to the 40hz horn as well. And the Seos24 will get a solid poplar mounting base. I'm planning on experimenting with some different horns as well, like JMLC and Tractrix horns.

                        Thanks!
                        Javad

                        --
                        Javad Shadzi
                        Bay Area, CA

                        2-Channel Stereo system in the works with Adcom components and 4-way towers

                        Comment


                        • #13
                          Originally posted by skatz View Post
                          Wow Javad, that is some piece of work.
                          Can you say more about how you calculated the compound angles? I have thought abut this before, thinking of using router bits for the angles, but got no farther than that; you are way ahead.
                          Also, the segments do need to join up I assume, how well are you able to match the sizes?
                          This site is very helpful, once you know the horn flare angle, then everything else is pretty easy to calculate: http://jansson.us/jcompound.html

                          Matching sizes is a matter of making sure the base outside flare width (wide side of the trapezoid) is the same as the base inside flare width (short side of the trapezoid) of the subsequent section. Helps to do lots of test pieces, once it all clicked in my head I'm more on autopilot now, but I had smoke coming from my ears for about 3 days before I made a first cut in wood! =)

                          Also read through my original post above, I tried to go into some detail, but if you need more clarification don't be afraid to ask, and I'll be even more detailed in the next pair I build now that I'm honing some of my techniques!

                          Thanks!
                          Javad
                          --
                          Javad Shadzi
                          Bay Area, CA

                          2-Channel Stereo system in the works with Adcom components and 4-way towers

                          Comment


                          • #14
                            I'm also building a bass reflex box for the 12" B&C 12PE32 so I can measure and listen to and compare to the horn, the port is also plug gable so I can test sealed as well.

                            The enclosure is 1 cubic foot which models well for this midbass and tuned to 90hz.



                            The port, 4" by about 1.5" tuned to 90hz

                            Thanks, Javad
                            --
                            Javad Shadzi
                            Bay Area, CA

                            2-Channel Stereo system in the works with Adcom components and 4-way towers

                            Comment


                            • #15
                              If you using 1.5" PVC as the port, the inside diameter is actually 1.61" - just in case it would affect your tuning.

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