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I theorize: 'Synchaeta'....a Minimus 7 revamp...

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  • I theorize: 'Synchaeta'....a Minimus 7 revamp...

    I'm awaiting the pictures from Bill to arrive taken from InDIYana before I do my official walkaround, so I felt I should do something else while I wait for them...

    Synchaeta is a rotifer, prevalent in both salt and fresh water, and capable of living very easily all over the world. Being they are small in size, the cabinet is a 'synch' to build, and it has prevalent applications for all sorts of sound systems, I dubbed the name appropriate. More on the cabs later.... (yes- I'm building these!)

    This has been brewing for awhile now, to revamp an old set of speakers many people have. I'm going to start off by drivers used, the PRV 4MR60-4, and the Dayton ND25FA-4, so this is in fact a 4 ohm system design. The specs have a high Qts on the PRV, and they were similar to the older Radio Shack 40-1030 4" that Matt and I swapped in for better results than the stock units.

    40-1030:



    PRV:



    Not only was it that it was close, but it was also higher sensitivity. The breakup wouldn't be hard to fix, so I modeled the stock specs and came up with this as a best compromise:

    Preliminary box:



    Well- I measured the PRV's today, and they measured quite a bit differently than they were spec'd:




    So- I have to remodel the box yet, but I'm confident it'll match the 40-1030 closer than originally intended. I'll update this in the future...

    On with the preliminary xover...






    It came out really nice and easy at 7 parts. I recommend 5W resistors where possible, and even rod-core or steel-core inductors to make the networks fit in the box. I wound a 1.2mH coil from 18AWG around a steel spacer from the hardware store for mine, and I wound the tweeter coil around the tweeter cap to save space in layout- pictures to come later. The 15 ohm 5W resistor will be soldered to the tweeter itself, and sits perfectly between it's terminals to do so. I'll likely solder the RC across the woofer's terminals for the same space concern reasons. Came out an asymmetric BW2/BW3 at 4.2k- not bad!

    More to come, thanks for looking!
    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

  • #2
    Re: I theorize: 'Synchaeta'....a Minimus 7 revamp...

    thanks ,
    subscribed

    Comment


    • #3
      Re: I theorize: 'Synchaeta'....a Minimus 7 revamp...

      Can't wait man!
      https://www.facebook.com/Mosaic-Audi...7373763888294/

      Comment


      • #4
        Re: I theorize: 'Synchaeta'....a Minimus 7 revamp...

        You see how close to the RS they match? That's just unbelievable!!!

        Oh- on test tones, the PRV actually played well up to 15k. The breakup was not really objectionable either, so my methods should work appropriately.

        This will happen...
        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


        • #5
          Re: I theorize: 'Synchaeta'....a Minimus 7 revamp...

          Originally posted by Wolf View Post

          Synchaeta is a rotifer, ...
          Wolf
          It's not often I have to use a dictionary on 2 of the first 4 words of a sentence.
          Isn't it about time we started answering rhetorical questions?

          Paul Carmody's DIY Audio Projects
          Twitter: @undefinition1

          Comment


          • #6
            Re: I theorize: 'Synchaeta'....a Minimus 7 revamp...

            I think I am probably missing something, but why not take the tweeter down to at least 3 KHz? It looks like that tweeter looks like it could do it with no sweat.

            Comment


            • #7
              Re: I theorize: 'Synchaeta'....a Minimus 7 revamp...

              Originally posted by fdieck View Post
              I think I am probably missing something, but why not take the tweeter down to at least 3 KHz? It looks like that tweeter looks like it could do it with no sweat.
              Ben and I talked about this when he started formulating the plan. Part of it is the crossover size. It's pretty small area to fit it into. And really look at that phase! That is just where these 2 meet up really well.
              https://www.facebook.com/Mosaic-Audi...7373763888294/

              Comment


              • #8
                Re: I theorize: 'Synchaeta'....a Minimus 7 revamp...

                Now I know... Understand the part about limited space. I updated the crossover on a pair of Pioneer B22s and it was a tight fit for two 100V film caps.

                Comment


                • #9
                  Re: I theorize: 'Synchaeta'....a Minimus 7 revamp...

                  Originally posted by Paul Carmody View Post
                  It's not often I have to use a dictionary on 2 of the first 4 words of a sentence.
                  My thoughts exactly.:D

                  Looks like a nifty little speaker, though.


                  Mark
                  You go your way, I'll go mine. I don't care if we get there on time.

                  ~Pink Floyd

                  Comment


                  • #10
                    Re: I theorize: 'Synchaeta'....a Minimus 7 revamp...

                    Originally posted by isaeagle4031 View Post
                    And really look at that phase! That is just where these 2 meet up really well.
                    I want to but I'm not sure which graph shows this. :(
                    People hear with their eyes.

                    Comment


                    • #11
                      Re: I theorize: 'Synchaeta'....a Minimus 7 revamp...

                      The very first one at the top. But honestly, looking at that plot, I wonder if Fred might not be right. Space considerations aside, it looks like the woofer, at least, might be happier crossing lower, even given the pretty reverse null. It seems that phase is tracking really nicely up to 1.5kHz, whereupon it diverges noticeably. I'm well aware that Ben has forgotten more than I'll ever know about this stuff, but I wonder, nonetheless.
                      You go your way, I'll go mine. I don't care if we get there on time.

                      ~Pink Floyd

                      Comment


                      • #12
                        Re: I theorize: 'Synchaeta'....a Minimus 7 revamp...

                        Dan look at the two orangeish and light blue lines in the pcd sim. That is the driver phase. They track each other very well especially at the crossover point. Then look at the reverse null (grey line in the pcd sim). Deep and narrow also identifies good phase tracking.
                        https://www.facebook.com/Mosaic-Audi...7373763888294/

                        Comment


                        • #13
                          Re: I theorize: 'Synchaeta'....a Minimus 7 revamp...

                          Originally posted by Mark65 View Post
                          The very first one at the top. But honestly, looking at that plot, I wonder if Fred might not be right. Space considerations aside, it looks like the woofer, at least, might be happier crossing lower, even given the pretty reverse null. It seems that phase is tracking really nicely up to 1.5kHz, whereupon it diverges noticeably. I'm well aware that Ben has forgotten more than I'll ever know about this stuff, but I wonder, nonetheless.
                          Another concern is the Qts of the tweeter being 1.5, and having a HUGE bump before rolloff. To tame that, this is where it fell. FWIW, I see good phase alignment from 200 Hz to about 7-8k before it spreads quite a bit. When you view the phase unwrapped, the departure you speak of at 1.5k is really very minor.

                          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


                          • #14
                            Re: I theorize: 'Synchaeta'....a Minimus 7 revamp...

                            Originally posted by isaeagle4031 View Post
                            Dan look at the two orangeish and light blue lines in the pcd sim. That is the driver phase. They track each other very well especially at the crossover point. Then look at the reverse null (grey line in the pcd sim). Deep and narrow also identifies good phase tracking.
                            As well as the plot below the system sim that I've attached above.

                            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


                            • #15
                              Re: I theorize: 'Synchaeta'....a Minimus 7 revamp...

                              Okay- the Box model looks a LOT better in that little box. Aperiodic really isn't necessary, and 8W yields Xmax that is reasonable all the way down at an output of 94dB. The best part- the F3 is 108Hz! That's almost a half-octave lower than prior. Sealed and stuffed!

                              The grit:




                              This is likely going to be better than I thought....

                              I'll be revising the Xover sim for accuracy next.
                              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

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