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Theorized and proven: "Zingers", an InDIYana 2019 8" 2-way design...

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  • Theorized and proven: "Zingers", an InDIYana 2019 8" 2-way design...

    I built these for the Bare Minimum challenge for InDIYana 2019. I've long wanted to build a 2-way with the SD215A-88, even when the older model, SD215-88, was around. The theme just gave me the excuse to do so. Yeah- I know what you're thinking... "An 8" subwoofer in a 2-way? That won't work!" However- it works rather well! The name comes from the toys and built up 1/32 scale models from the '70s, as well as those related to Rat Fink, et al. Basically, a large performance motor crammed into a chassis that had nowhere near enough volume for it to occupy the destination without some major changes. This wasn't that drastic of a shoehorn, but the namesake still applies hearkening to the larger woofer 2-ways of old, as well as the bigger motor in a small box mantra. The following will lay out the pertinent information.

    I'm going to start off by saying these should have been characterized as a build that was done all wrong. I didn't round the baffle edges to reduce diffraction. I didn't round the port exit to reduce turbulence, even though the inner end is angled for a utilized flare. I didn't flush-mount the woofer, as it had to mount atop of the tweeter for a closer CTC distance. I used an 8" in a 2-way, which is seldom done well, and even more often unsuccessfully. Then I was limited to use 5 parts per the challenge- which was listenable- but I preferred the addition of a 6th part to make it as good as I felt it could be without much more complexity. I had 2 weeks to assemble, measure, listen, and verify results. And lastly- I finished the baffle first before I cut the drivers' locations so the tear-out would be minimized. Suffice to say the odds were stacked against me.

    I've been a fan of these woofers since 2007 when I heard them in Paul Carmody's 'Aethers' design at Iowa DIY. The bass was solid, deeply extended, and pretty well defined for a driver of that price. It was utilized in a 1.5ft^3 vented box for an F3 of 29Hz at that time. While it would likely still apply to this design by elongating the cabinet a bit, I shrunk the volume to 1ft^3 and lost 5Hz off the bottom end in extension. Using real T/S as follows:

    As in the Aethers:

    Click image for larger version  Name:	Zinger-LargeBox.jpg Views:	1 Size:	183.2 KB ID:	1412016

    As used here in the Zingers:

    Click image for larger version  Name:	Zinger-SmallBox.jpg Views:	1 Size:	182.0 KB ID:	1412017

    Next step was a logical look and layout to make them buildable:

    Click image for larger version  Name:	Zingers.png Views:	1 Size:	404.0 KB ID:	1412018

    I was able to get these constructed with bracing from a 2' x 4' MDF Handipanel and another plywood panel of the same. I only used half the ply for the 2 baffles, and required minimal scrap MDF to complete the boxes. All panels are tied into the bracing scheme, even the baffles between the W/T and just below the woofer. I used a side-exit port this time around just to be different and to the fact these might end up against a wall. The cabs had a barrier of rolled on RedGard applied to the inside walls. Ed Froste always swore by this elastomeric shower moisture barrier product inside his boxes. I finally clicked this method on my building bucket-list. It is messy, but it does damp the walls a bit, as well as seal the inside rather nicely.

    Click image for larger version  Name:	IMG_4327.JPG Views:	1 Size:	63.1 KB ID:	1412019

    The terminals were from a large bag of binding posts that did not have the jam nut, solder-ring, isolation washers, or the outer free-wheeling nut to clamp down on the wire/spade. I had to devise a solution to use these, and it turns out they will thread into a 9/16" hole, half-inch thick, rather nicely from the inside. I soldered leads, shrunk some heatshrink around them, and installed them by hand. I laid some E6000 adhesive over the collars and all was done. Note to self- make tool to install posts this way to avoid massive blisters and bloody knuckles. I have the hand strength to get them threaded in, but my fingers weren't happy, and my knuckles kept getting scraped on the RedGard stuff. In the end, this leaves a nice pair of 'Nanner-Only' connections:

    Click image for larger version  Name:	IMG_4320.JPG Views:	1 Size:	53.5 KB ID:	1412020

    More in the next post...
    Wolf

    EDIT: The 5.325" dimension in the baffle and size layout is incorrect. The tweeter to top, and CTC is accurate, so please use those for dimensional agreement, and allow the woofer to bottom to be the variable unknown. Drawing is not to scale.
    Last edited by Wolf; 05-03-2019, 05:26 AM.
    "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
    I happened to have a pair of Peerless DA25BG08-06 tweeters on hand, and thought these would be a good tweeter to pair the SD215A-88 with. They have a low enough Fs, low cost, and a really nice sound I'd heard in a few others' builds before. They are touted as being able to xover fairly low in their spec sheet as well. Their sensitivity was also high enough that they should have enough output to keep up with an 8" DVC woofer wired in parallel. I also wanted to be different and not use a waveguide or the newer RST tweeters since those seem to be the latest hot-ticket items.

    Click image for larger version

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    Click image for larger version

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    Woofers in box:

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    Tuning verified! On-tweeter-axis and 20* H off-axis measurements for both units were then taken as you see here:

    Click image for larger version

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    Did I mention that the ply I found had a really nice figured veneer already applied? A bit of Watco Danish oil and a couple wipe-on polyurethane coats are all this took.
    Measurements up next...
    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


    • #3
      Left speaker measurements; on-axis/20*H/HD:

      Click image for larger version

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      Click image for larger version

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      Click image for larger version

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      Woofer at same mic position:

      Click image for larger version

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      Click image for larger version

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      To be continued...
      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


      • #4
        Click image for larger version

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        You can see here that the HD of the woofer and tweeter really are not awful being -35dB from reference for the woofers, and even lower for the tweeters. They might not be world-class SOTA low HD, but it's still quite decent. The added benefit of the HD inherently reducing itself above about 1.2kHz is a welcomed bonus on the woofers.

        And to also show the right channel...

        Click image for larger version

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        Click image for larger version

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        Click image for larger version

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        Woofer nearfield:

        Click image for larger version

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        More to come...
        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
          You can see the breakup for the woofer was in different places for the left channel (above, 2.5K) and the right channel (below, 1.9k).

          Click image for larger version

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          Click image for larger version

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          Click image for larger version

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          Since the right channel FR measured closer to the spec sheet, I used it as info in the initial sim, and made sure off-axis FRs, and the left channel FRs did not produce any peaking with the simulated schematic.
          This is what I came up with for the on tweeter axis right channel FR:

          Click image for larger version

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          The impedance and phase angle make for a relatively benign load, albeit a 4 ohm nominal load. The breakup is reduced enough that I did not find it (them) audible. The acoustic phase (not shown) was about 90 degrees out, so this is likely closer to a Butterworth alignment than an LR, but I do get a very narrow reverse null that dips to -20dB from reference. I'm assuming more parts can make it better aligned, but since the off-axis is not causing issues, I'm leaving it alone! Xover point came out about 1850Hz. Second order electrical on the woofer rolls it off fairly well. The tweeter is second order as well with a series resistor for level, and an added parallel resistor for Fs compensation. Trust me- it needed it!

          Network is as follows:

          Click image for larger version

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          Just a bit more...
          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


          • #6
            I was able to get the network on a 4" x 7" board relatively easily. Yes- you do see 2 other twisted taps on the xover's LP coils. I wound those in my jig so I had 2 other options to play with. I had 1.8mH, 2.0mH and 2.2mH (simmed), and wound up (HA! LOL!) at the 2.2mH level. I tried 7.6, 8.2, and 9.1 ohms for the 1st resistor on the tweeter. 7.6 was not enough, 9.1 was dull, and 8.2 might be just a touch over. Then I added the 33 ohm across the tweeter, and it came into the right spot as well as reducing the grit/glare/nasality.

            Click image for larger version

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            Total cost as built came out to about $240 with the parts I used. $111 or so in drivers, and guesstimating on the xover parts I used since some are NLA. Using 250V CSA caps drops the cost to about $230 total.

            FWIW, I really like these! Bass for days that extends really low, sensitivity that is in the upper 80s, and a size factor that won't make most builders cringe. Top it off with an affordable cost, and these are a very easy project to stomach that would gut punch you with bass if you said otherwise.

            I look to get actual measurements of the final responses and post them in the near future, as I've not verified them as yet.

            Thanks for looking, and hope you find these interesting.
            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


            • #7
              I sure would enjoy hearing these.

              Comment


              • #8
                I'm going to look for some CL cabs to make these.

                Comment


                • #9
                  Very cool! Keep us posted.
                  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


                  • #10
                    I liked these, very easy to listen to. Not sure why they didn't stand out of the tough crowd in your group, but I'm sure the more challenging tracks with the deep bass would have put them in a better spot. I can't speak for anyone else in the room, but when I hear 40Hzish notes filling the room my attention is piqued. I'm a little bass biased

                    djg CL?... my guess is constrained layer, is that right?
                    Electronics engineer, woofer enthusiast, and musician.
                    Wogg Music
                    Published projects: PPA100 Bass Guitar Amp, ISO El-Cheapo Sub, Indy 8 2.1 powered sub, MicroSat, SuperNova Minimus

                    Comment


                    • #11
                      I really liked these, I voted for them.

                      Comment


                      • #12
                        CL = craigslist. As in $20 vintage rotted foam driver cabs. Most I've seen are taller and shallower than the design calls for. I think this could be a very popular design.

                        Comment


                        • #13
                          Cool build Wolf.

                          Comment


                          • #14
                            I'll also add that, you've been lucking-out on the veneer front, that is a lovely baffle.

                            Comment


                            • #15
                              Nice to see some wood, Benny! Will these show up at MWAF this year?
                              A mains
                              The Ventures
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