Announcement

Collapse
No announcement yet.

Chamfer vs. Roundover?

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

  • #31
    Re: Chamfer vs. Roundover?

    Originally posted by Jeff B. View Post
    Well, it would work fine for randomizing wavelengths, but would sure look strange. Properly postioned strips could do the same thing and be much more appealing to look at.
    What- no sense of art? :p
    Might look neat-o with the right tweeter...
    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


    • #32
      quasi-spherical wavefront source

      Assuming Geddes is right, what IS the optimum curvature for the available quasi-spherical wavefront source?
      I remember that Martin Colloms touched upon this subject back in the 1980's in his book "High Performance Loudspeakers" (pp.304-306, Fourth Ed., Wiley Press). I highly recommend this book.

      His description refers to a "shallow contoured horn, properly curved to provide a termination at right angles to the dome circumference...the edge of the dome then sees a matched acoustic mirror and the sound wave is launched without distortion".

      His illustration looked similar to the (crude) diagram below:

      Obviously, much progress has been made in this area. The JBL waveguide referenced by Zilch looks great- I wonder if this could be adapted to work with my XT25 ring radiators...
      Attached Files
      Last edited by Chas; 01-17-2010, 08:35 AM. Reason: Correct typo

      Comment


      • #33
        Re: Chamfer vs. Roundover?

        O.K., so how about if we want a spherical wavefront with defined and controlled directivity, launched asymmetrically so as not to generate a notch in the on-axis response from the exit?

        Comment


        • #34
          O.K., so how about if we want a spherical wavefront...launched asymmetrically so as not to generate a notch in the on-axis response from the exit?
          Turns out that Colloms was referring to the work of Hayakawa, et al (Kenwood) back in the 80's; see:

          http://www.aes.org/e-lib/browse.cfm?elib=5138

          I couldn't find any diagrams online, so I'm including a scan from the book
          "High Performance Loudspeakers", Fourth Edition, 1991, Wiley Press (Buy the book!). I hope there is no rule against posting this, as I have given proper credit to the source.

          Note the resulting frequency responses, especially on-axis. As far as "defined and controlled directivity", I'll leave it to others here to comment...
          Attached Files
          Last edited by Chas; 01-17-2010, 08:40 AM. Reason: attach image

          Comment


          • #35
            http://www.madisound.com/catalog/PDF/h1499.pdf

            Here's the JBL LSR EOS and mating 053TiS tweeter:



            Attached Files
            Last edited by Zilch; 01-18-2010, 07:46 PM.

            Comment


            • #36
              Re: Chamfer vs. Roundover?

              Originally posted by Chas View Post
              Turns out that Colloms was referring to the work of Hayakawa, et al (Kenwood) back in the 80's; see:

              http://www.aes.org/e-lib/browse.cfm?elib=5138

              I couldn't find any diagrams online, so I'm including a scan from the book
              "High Performance Loudspeakers", Fourth Edition, 1991, Wiley Press (Buy the book!). I hope there is no rule against posting this, as I have given proper credit to the source.

              Note the resulting frequency responses, especially on-axis. As far as "defined and controlled directivity", I'll leave it to others here to comment...


              That looks great actually. A 1st order HP filter would give you completely flat response from 5KHz on up, with the off axis response being unchanged from the on axis response, other than level.
              R = h/(2*pi*m*c) and don't you forget it! || Periodic Table as redrawn by Marshall Freerks and Ignatius Schumacher || King Crimson Radio
              Byzantium Project & Build Thread || MiniByzy Build Thread || 3 x Peerless 850439 HDS 3-way || 8" 2-way - RS28A/B&C8BG51

              95% of Climate Models Agree: The Observations Must be Wrong
              "Gravitational systems are the ashes of prior electrical systems.". - Hannes Alfven, Nobel Laureate, Plasma physicist.

              Comment


              • #37
                Re: Chamfer vs. Roundover?

                Here's the DXT:


                http://www.seas.no/index.php?option=...274&Itemid=248

                And as Zaph measured it:


                http://www.zaphaudio.com/offaxis.html
                Attached Files

                Comment


                • #38
                  Re:http:dxt tweeter

                  Here's the DXT
                  I'd like to thank dlr for his interesting analysis of the DXT; It makes for an interesting and enlightening read:

                  http://www.speakerdesign.net/seas/tw...t_tweeter.html

                  For instance, I didn't think the screw holes in the faceplate had such a noticeable effect on F.R. within the audible range.

                  Maybe I'll try using the DXT in my next project...

                  -Chas

                  Comment


                  • #39
                    Re: Chamfer vs. Roundover?

                    The principles are well worn:

                    http://www.lansingheritage.org/html/...nical/lens.htm

                    Geddes links HOMs with diffraction, and I'd expect DXT to be no exception.

                    I heard Mark's at the NorCal meet, and liked them, perhaps primarily for their constant directivity and uniform power response.

                    In any case, the Seas white paper is very specific about that obviating the necessity for cab edge treatments, so I'm including it as evidence here, independent of its different derivation.

                    I'll be getting up close and personal with DXT for comparison to my favorite waveguides.... :D

                    Comment

                    Working...
                    X