Announcement

Collapse

Midwest Audio Fest

It’s that time audio enthusiasts! Registration for the 2019 Speaker Design Competition is now open! Visit midwestaudiofest.com for details and to list your speaker project. We are excited to see all returning participants, and look forward to meeting some new designers this year, as well! Be sure your plans include a visit to the Parts Express Tent Sale for the lowest prices of the year, and the Audio Swap Meet where you can buy and trade with other audio fans. We hope to see you this summer! Vivian and Jill
See more
See less

Help understanding types of horns

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

  • Help understanding types of horns

    Hi Everyone,

    I ran across the Duevel line of omnidirectional speakers the other day, and I've been trying to find some clear research / literature on the different types of horn profiles that are used... and WHY you'd use one type of horn profile over another.

    In the case of the Duevel Bella Luna, they use a compression driver mounted on a carved wooden horn, with some kind of exponential cone suspended in it like a trombone mute. I understand they are trying to encourage a 360 degree donut of sound (not exactly a true omnidirectional design... but close enough from a seated listening position?)... but how did they arrive at that design? Some publically available knowledge that I haven't run across on Google? Or more likely trial and error with the geometry and spacing of the horn vs. "mute" positions?

    At any rate - Understanding the Duevel design is kind of secondary to the base question... why would I choose, say, an exponential horn over a tractrix horn design? I can't seem to find clear documentation that compares strengths and weaknesses of each design.

    Thoughts?

    Thanks!

    Click image for larger version

Name:	BLSchnitt.jpg
Views:	1
Size:	53.4 KB
ID:	1414071
    Voxel Down Firing with Dayton SA70
    Translam Subwoofers - The Jedi Mind Tricks
    The Super Bees - Garage 2 way
    SevenSixTwo - InDIYana 2018 Coax
    The Defiants - InDIYana 2019 "Bare Minimum" Build

  • #2
    Keith

    if you go to volvotreter.de, under the downloads-articles, you can find a bunch of papers by Bruce Edgar that were published in Speaker Builder in the 80s, about his horn designs. There is also an interview with him.
    Collectively these have some of what you want. They are interesting reads anyway. Back in those days I made some of his tractrix horns, and had many phone conversations with him. He was rather long winded but very friendly. The interview probably has the most about different design types.
    I suspect most of what you want is in AES papers, but I don't have access to those. I have some books of collections of AES papers somewhere, but its not easily gotten. HornRespose may contain some of this in its help section. Haven 't looked on DIYaudio, but I think you might find it there as well.

    Steve

    Comment


    • #3
      Originally posted by skatz View Post
      Keith

      if you go to volvotreter.de, under the downloads-articles, you can find a bunch of papers by Bruce Edgar that were published in Speaker Builder in the 80s, about his horn designs. There is also an interview with him.
      Collectively these have some of what you want. They are interesting reads anyway. Back in those days I made some of his tractrix horns, and had many phone conversations with him. He was rather long winded but very friendly. The interview probably has the most about different design types.
      I suspect most of what you want is in AES papers, but I don't have access to those. I have some books of collections of AES papers somewhere, but its not easily gotten. HornRespose may contain some of this in its help section. Haven 't looked on DIYaudio, but I think you might find it there as well.

      Steve
      Thanks Steve - I'll have a look at that site. I haven't been there yet! Basically I'm after any info that would guide a design process if I wanted to try and replicate the Duevel design philosophy for myself.
      Voxel Down Firing with Dayton SA70
      Translam Subwoofers - The Jedi Mind Tricks
      The Super Bees - Garage 2 way
      SevenSixTwo - InDIYana 2018 Coax
      The Defiants - InDIYana 2019 "Bare Minimum" Build

      Comment


      • #4
        Here are some articles I have saved: Google Drive - Horn Design

        Comment


        • #5
          I imagine a possible issue with the Duevel system in the pic is energy bouncing off that deflector and right back at the cone, introducing distortion.

          Comment


          • #6
            Originally posted by philthien View Post
            I imagine a possible issue with the Duevel system in the pic is energy bouncing off that deflector and right back at the cone, introducing distortion.
            Yeah Phil, I agree... must be part of the compromise in making this design. I see a lot of speakers marketed as "omnidirectional" employing that kind of cone-over-woofer arrangement to get dispersion. Either there's something to it, or it's a rampant case of Monkey See, Monkey Do.
            Voxel Down Firing with Dayton SA70
            Translam Subwoofers - The Jedi Mind Tricks
            The Super Bees - Garage 2 way
            SevenSixTwo - InDIYana 2018 Coax
            The Defiants - InDIYana 2019 "Bare Minimum" Build

            Comment


            • #7
              The Duevel HF section is still simply a horn, but it's geometry is made so that it takes the sound pressure wave from the down-firing compression driver and diverts it outward, radially. If you look at the total cross-sectional area as you move from the throat to the mouth, you would see a similar horn loading that you will see on a "straight" horn with equal cross-sectional area. I've built one similar to that shown above as a prototype for a project. Unfortunately, I haven't found the time to finish up the project.

              Comment


              • #8
                Some horn designs also use phase plug theory, which is kind of an interesting mechanical filter you can add to your horn. Horn Response program is a way to convert horn theory into practical designs. There is tons of Horn Response info on another forum.
                John H

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

                Comment


                • #9
                  Thanks jhollander and 1100xxben , I haven't messed with Horn Response yet.

                  Ben - I think you said the Duevel design is simply a horn with a diverter of equivalent contour sitting in front of it (like a perfect fit negative of the horn if you made a casting inside it). If I were travelling down the wall of the horn, it would be same distance from my "floor" on the horn to the "ceiling" of the diverter... I guess I just give folks more credit and assume the designs are more complicated than they might be!
                  Voxel Down Firing with Dayton SA70
                  Translam Subwoofers - The Jedi Mind Tricks
                  The Super Bees - Garage 2 way
                  SevenSixTwo - InDIYana 2018 Coax
                  The Defiants - InDIYana 2019 "Bare Minimum" Build

                  Comment


                  • #10
                    A while back, dlneubec was trying a Duevel-inspired build. He had 6(?) of the Dayton 12" waveguides, a pair of RS270, and a set of TLabs tweeters. The lower waveguide for the woofer set on the phase plug of the RS driver. The second was bolted to the first for the lower side of the upper horn, and the top one was the upper portion and mounted to the tweeter, so exit was between the upper 2.

                    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


                    • #11
                      Originally posted by KEtheredge87 View Post

                      Thanks Steve - I'll have a look at that site. I haven't been there yet! Basically I'm after any info that would guide a design process if I wanted to try and replicate the Duevel design philosophy for myself.
                      Well, you can follow Bruce Edgar as he learned about horn design. Just be aware that that was in the 80s, a lot has happened since. And HornResponse didn't exist then.

                      Comment


                      • #12
                        I think you need to go back to basics. We have dropped part of the name of what is occurring , horn loaded, for convenience. With a horn you are changing the load of the driver. Different horns load the driver in different ways. So looking at how the load of the horn effects the impedance of the driver is a good way to start to understand horn types. Hope this maybe helps.
                        one more thought to toss in. Many designs that clain to be horns are not, they are actually just wave guides. We like to interchange horns and wavr guides and they are two very different things.
                        craigk

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

                        Comment


                        • #13
                          Originally posted by craigk View Post
                          I think you need to go back to basics. We have dropped part of the name of what is occurring , horn loaded, for convenience. With a horn you are changing the load of the driver. Different horns load the driver in different ways. So looking at how the load of the horn effects the impedance of the driver is a good way to start to understand horn types. Hope this maybe helps.
                          one more thought to toss in. Many designs that clain to be horns are not, they are actually just wave guides. We like to interchange horns and wavr guides and they are two very different things.
                          Thanks Craig. You are correct that I need a good lesson in the fundamentals of horns, including horn loading of the driver. I've started to read through the papers and links that have been provided above, but I haven't had the "loading" idea click in my head yet. Something about the horn helping to correct the acoustic/physical impedance mismatch between the air at the mouth and the air at the throat of the horn... and then as you say how that horn loading impacts the electrical impedance of the horn driver itself.

                          I have a LOT to learn!
                          Voxel Down Firing with Dayton SA70
                          Translam Subwoofers - The Jedi Mind Tricks
                          The Super Bees - Garage 2 way
                          SevenSixTwo - InDIYana 2018 Coax
                          The Defiants - InDIYana 2019 "Bare Minimum" Build

                          Comment


                          • #14
                            Originally posted by KEtheredge87 View Post
                            At any rate - Understanding the Duevel design is kind of secondary to the base question... why would I choose, say, an exponential horn over a tractrix horn design? I can't seem to find clear documentation that compares strengths and weaknesses of each design.

                            Thoughts?
                            An interesting design challenge. If you want to learn about the pros and cons of different horn types (hyperbolic, conical, elliptical,...) and how to model them with lumped equivalent circuits in the manner of cabinets and drivers then the most useful source is probably a text book on the fundamentals of acoustics. There are a number often originally written around the 50s and revised. "Acoustics" by Beranek would be one example but there are others. The reason for recommending a text book is that the details in the chapters on horns will depend on other things like radiation impedance, equivalent circuits,... which are explained in other chapters of the same book. It can be a lot harder work sorting this out when working from papers and articles.

                            However, your design does not involve a straight horn but one that progressively turns through 90 degrees which progressively uses an increasing radius to increase the cross sectional area. Although the rate of change of area with distance down the horn is likely to read across fairly well in terms of loading the maths of the wall profiles will be completely different. At a guess the dominant factor in terms of sound quality will be how to maintain as close to 90 degrees as possible the angle the wave front travelling down the horn makes with the guiding walls. Any deviation from 90 degrees will create a reflected wave and put energy into the acoustic modes of the duct/horn. In a wide angled waveguide the effect is weak but in a deep horn it creates a characteristic sound that was often called horn honk.

                            Today an engineer would not use equivalent circuits to tackle a design problem like this but 2D (the horn is axisymmetric) or full 3D computer software to model the acoustic waves from the diaphragm, through the throat (important region that forms the shape of the wavefront for the horn), down the horn, and out into the room taking account of the shape of the baffle. There are a few awkward to use but freely available programs like Acousto, ABEC or Elmer that may be able to make a decent stab at this (there are others as well). COMSOL is an example of fully developed commercial software that would tend to be used by industry.

                            Comment


                            • #15
                              KEtheredge87 - I"d advise some time in Hornresp. After a few dozen hours, I can now design straight MLTL and TWQT in Hornresp, but apparently it can also model exponential and other shapes.
                              There is a Hornresp forum in DiyAudio/Subwoofers. You can also Google "Hornresp exponential" and come up with some stuff. Hornresp has a steep learning curve, but for me it's the best way, since I don't have a deep math background.
                              Hope this helps.

                              I think I hear a difference - wow, it's amazing!" Ethan Winer: audio myths
                              "As God is my witness I'll never be without a good pair of speakers!" Scarlett O'Hara

                              High value, high quality RS150/TB28-537SH bookshelf - TARGAS NLA!
                              SB13/Vifa BC25SC06 MTM DCR Galeons-SB13-MTM
                              My Voxel min sub Yet-another-Voxel-build

                              Tangband W6-sub

                              Comment

                              Working...
                              X