Announcement

Collapse
No announcement yet.

Dodecahedron Project

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

  • Dodecahedron Project

    Hi all,
    I just now joined this forum hoping to get some advice and technical knowledge that would allow me to move forward with my speaker project.
    1. My brother is an expert wood-smith, and I desire two miniature versions of the old Design Acoustics D12 (dodecahedron-shaped) hanging from the ceiling above my existing speakers. Each would be full of super-tweeters and their purpose would be to supplement the existing sound with omnidirectional sonic and ultrasonic highs (and admittedly, the aesthetics of the miniature dodecahedrons hanging in my corners).
    I envision 10 super-tweeters, one on each side of the dodecahedron except the top and bottom (unless y'all think I should include a midrange driver on top).
    I’m not versed in the engineering and know not about crossover networks, impedance, power distribution, etc.
    Here’s the first questions that come to mind:
    Advice on which super-tweeters to buy: I want the high-end frequency to be well above audible; quality vs. price matters (I’ll need twenty of them); and need them to be small in order to minimize the size of the cabinet;
    What is the circuitry, or how are they wired, such that they would supplement whatever full-range house speakers I might have in place;
    Whether inclusion of a mid range driver is a better choice.
    Any guidance would be greatly appreciated - THANKS!
    Brad

  • #2
    Do you own a dog?

    Who knew?

    https://en.wikipedia.org/wiki/Dodecahedron

    Comment


    • #3
      The problem with this arrangement is comb filtering. That, not the woodworking complexity, is why you seldom see this scheme employed.
      www.billfitzmaurice.com
      www.billfitzmaurice.info/forum

      Comment


      • #4
        Yeah, that will look pretty cool. Like Bill said though, won't work very well as a speaker. So if you do it, it's probably not worth super expensive tweeters. I'd get the tiniest ones I could find, meant for mounting in a car door sill etc.
        Francis

        Comment


        • #5
          I was going to suggest (assuming their flying/mounting is stable enough to avoid them rotating) to only actually run one of the more ideally positioned tweeters live and leave the rest as decorative only to avoid combing while still getting the additional highs you want.
          Then I realized this is probably not going to hang super close to the other speakers, so driver spacing might be an issue anyway, particularly if the already existing speakers have a decent tweeter of their own. If this is the case, it might be better to create the dodecahedron as purely decorative along with some thin but also decorative wireing to make it appear "live".
          If the 10sider WILL be spaced fairly close to the existing speakers and you can use a single tweeter from it in place of the tweeter in the existing speaker, then I don't think it'll be a problem as long as you can cross them over to play nice with each other...but it's probably more work than it's worth compared to simply making it a very interesting decoration that can use cheaper (but still pretty) tweeters and no real wiring nor any crossover.

          If your existing speakers already sound good, adding these in a working fashion shouldn't noticeably change how things sound (best case) or they may easily make things sound worse (worst case), so making them non-functional might be a way to keep the best sound while still getting the very interesting appearance and avoiding some headaches. If your existing speakers don't sound good, it's still probably better sound-wise to improve their existing tweeter/crossover unless these new ones will fly pretty close and you can pair them up really well.
          My first 2way build

          Comment


          • #6
            I've always liked that concept. The issue for me would be separating the highs from the main speakers. That will mess up the imaging. Any concept of omni or reflecting speakers closer to the main speakers would be better imo.
            John H

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

            Comment


            • #7
              I am puzzled by what you are hoping to achieve. You said yourself that you want ultrasonic inaudible results. So what benefit are you looking for? I understand the omni part, but not the inaudible.

              Comment


              • #8
                Thanks all, I’m glad I found this and asked!
                I googled “comb filtering” and I get it. Sounds not only like an issue of new vs. pre-existing, but also a fundamental issue with the concept of bouncing the highs off of walls along varying path-lengths (oh crap, that bums me out).
                The reason I’m drawn to the higher-than-audible frequencies is because when my ears were much younger, it seemed like super-tweeters made the music sound more… real, or live, or something. Right or wrong, I seem to have carried the memory of that sound.
                Anyways, I envisioned them hanging directly above my already excellent sounding speakers, and I wouldn’t do the project for looks only.
                Thoughts? Thanks! Brad

                Comment


                • #9
                  Sounds like the circuitry associated with having these live there, and supplementing whatever full-range speakers I have in place, is no small matter either.

                  Comment


                  • #10
                    Originally posted by Brad Olsen View Post
                    [The reason I’m drawn to the higher-than-audible frequencies is because when my ears were much younger, it seemed like super-tweeters made the music sound more… real, or live, or something. Right or wrong, I seem to have carried the memory of that sound.
                    It may never again be more than a memory. The ability to hear high frequencies continually diminishes with age, starting around 20. There are so-called 'teenager repellent' devices that are tweeters that broadcast an irritating 18 to 20kHz tone. Teenagers can hear them, older folks can't.

                    www.billfitzmaurice.com
                    www.billfitzmaurice.info/forum

                    Comment


                    • #11
                      at 40 years old I could still hear 16k, barely. At 55 yo, I can hear 12k, barely. 10 I can still hear well. Hopefully for a few ore years yet

                      Comment


                      • #12
                        Brilliant feedback and THANK YOU!!. So now I need a different excuse to make these and have them hanging in my corners...

                        Comment


                        • #13
                          Sounds like a fun project to me. My opinion is that comb filtering is not an issue for you to be concerned with, especially with the supertweeter concept and the fact that you are listening from a fair distance. Our aural cues for location are generally considered to be highest in our ears most sensitive range, which is generally considered in the 2-6khz range. Have you ever noticed that super high frequencies are actually quite hard to locate. You will want to use a fairly small cap to roll off the response below perhaps 8 khz or so, I don't think you will notice any effect of comb filtering, since you are essentially splashing the frequencies above all over the room and most of what you hear will be reflected sound, which is what you want if you desire to expand the apparent soundstage width and depth, sense of realism and airiness, rather than to improve imaging. The press fit Dayton ND16FA-6 would be a good choice.

                          I think what you are after is mainly horizontal dispersion in an omni-polar fashion. The dodecahedron is a cool look, but you might consider a simple vertical tube or vertical octagon shape and maybe 8 supertweeters arranged horizontally in an array, all at the same height. This may not he the cool look you are going for, but it might be more effective, particularly if you could set them on top of your existing speakers, getting this sound source closer to the other drivers and a little closer to ear height, both of which are probably good things. I say go for it and have fun!
                          Dan N.

                          Comment


                          • #14
                            On the other hand ' comb filtering ' can be a pleasurable effect .
                            There is ' sound ' beyond ' fidelity '

                            Comment


                            • #15
                              First step would be to determine how big you want the dodecahedron to be, which will affect how big each panel is and directly how large the speaker on that panel can be, and how much you want to spend. 20 drivers at even $15 each is $300+crossover parts, so more like an easy $400. Minor for some, considerable for others.

                              Assuming these are going to be smaller than a soccer ball, the panels probably cannot handle a standard 4" tweeter plate. As dlneubec mentioned, the ND16FA-6 is a good small form tweeter that is also inexpensive.

                              Personally, I would try to get a design where you can fit a 2" diameter midrange on a panel. Then I would use 4 of those arranged in a reasonable pattern, along with 6 of the ND16FA-6 or similar, leaving the top and bottom panels with nothing on them. Depending on what you land on, the friendly folks here can help out with a crossover design and you'll have a cool non-traditional speaker set that should make great sound with a separate sub. They may not image the best but there can be more to great sound than ultimate fidelity.


                              Last edited by Dukk; 06-05-2020, 02:51 PM.

                              Comment

                              Working...
                              X