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  • GANDI Design Build Thread

    Hope I'm not violating the terms of use for Tech Talk.
    The driver is NLA, and I'm not posting any links.

    A few weeks, ago another distributor had a closeout sale of Gradient Acoustics drivers of various sizes.
    After a bit of Googling, it appeared that these were well-regarded, if not really great, so I picked a quad of the 4 inch
    mid-woofers in kevlar/paper - the AXT-04

    Another user here suggested a TM with the ND20 and I committed to the design.
    I may use a pair of ND25 tweeters I have, or I may decide to use a better tweeter.
    Early days though, I'll make that decision after I've listened to them a bit.

    Here is the manufacturers info:
    Click image for larger version

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    Last edited by donradick; 09-26-2017, 05:57 PM. Reason: added tag

    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

  • #2
    I wanted to build a desktop / computer speaker (because that's what I need, and that's what everyone requests)
    So probably 4-5 liters max.
    Quick Unibox model showed that a sealed alignment was a no-go (exceeded xmax at 100 Hz).
    Here is the model for a 4 liter box tuned to 65Hz with a 1 inch port.

    Doesn't look bad except for port speed. wow. way over the limits.

    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


    • #3
      Second Unibox model. Fixed the port speed issue.

      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


      • #4
        Third model - tried to lower the box tuning to 55 Hz.
        Problem is that xmax is still exceeded at about 57 Hz. Makes me nervous.

        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


        • #5
          I'm always amazed by this change - make the box a bit smaller and it helps with xmax

          A bit more of an EBS alignment, but I'll bet room and boundary gain will fill that in.
          Xmax is now exceeded only below 47 Hz much better.
          Port length is a little long, but there are ways to deal with that.

          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


          • #6
            Final model - my notes:

            TRY SMALLER BOX and even lower tuning

            3.0 liter 1.25 inch port 50 Hz Fb 12W notes.
            add some stuffing (Qa = 10) and helps xmax
            can take 18W before xmax exceeded = 99 dB

            EBS rolloff FR
            99 dB max - with 18 watts not likely to need that much
            F3 = 103
            F6 = 70
            F10 = 42
            XMAX exceeded at 43 Hz
            Port speed 26 m/s marginal, but not likely to play at 99 dB
            Port length 32cm / 12.5 inches - too long

            So I'll just build a slot port.....
            One of the neat things about this approach is that making the port
            a little longer improves FR and lowers xmax Hz.

            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


            • #7
              I'll be following this. The AXT-04 looked like an excellent driver and a steal of a deal.

              How will you handle xmax below 50 hz?

              Comment


              • #8
                What about a basic line level high pass circuit before the amp for excursion control?
                Projects:

                transcenD: http://techtalk.parts-express.com/fo...5035-transcend
                Summits: http://techtalk.parts-express.com/sh...75-The-Summits
                References: http://techtalk.parts-express.com/sh...-My-References
                Vintage Style 2-way: http://techtalk.parts-express.com/sh...-vintage-2-way

                Comment


                • #9
                  using data from here:
                  https://www.gradient-acoustics.com/P...en,7600,156426

                  My initial thoughts were (I'm still learning...):
                  4 liters with 1.375" ID port x 5" long gives Fb 68 Hz, F3/6/10 = 61/55/50 Hz
                  computer speakers so narrow baffle width 5" using 1/2" MDF, height 10 inches or so to keep drivers at ear level when seated at keyboard, depth about 6".

                  But now after learning from your posts above, I'm really liking the idea of making it smaller (3 liters) and using a slot port

                  I was lucky enough to pick up both drivers on sale (AXT-04 and the ND20FA-6) and am looking forward to learning from this build. I know that the ND20s aren't the fanciest tweeters, but when looking at designs like the Quarks, it appears that they can be tamed and made to sing quite nicely.


                  Comment


                  • #10
                    Originally posted by Millstonemike View Post
                    I'll be following this. The AXT-04 looked like an excellent driver and a steal of a deal.

                    How will you handle xmax below 50 hz?

                    I"m using the Quarks as my guide.
                    I used them for a long time as Desktop/Computer speakers, and even used them for a while full range for my HTR front L+R mains
                    and really didn't notice any distress at "normal" listening levels. Now that I've measured a whole bunch of speakers, I know that
                    90dB is quite loud, and I don't plan on running these that loud.

                    I wasn't comfortable in the first model with xmax exceeded at 57 Hz - lots of music in that area.
                    I'm much more comfortable with the 4th model, xmax exceeded at 43 Hz.

                    We shall see, but I feel pretty good about the final model.

                    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


                    • #11
                      Originally posted by dynamo View Post
                      What about a basic line level high pass circuit before the amp for excursion control?

                      That's certainly possible. For me, if the speaker needs protection, I'm likely to put a large cap inline for 1st order bass protection.

                      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


                      • #12
                        Originally posted by ceiol View Post
                        using data from here:
                        https://www.gradient-acoustics.com/P...en,7600,156426

                        My initial thoughts were (I'm still learning...):
                        4 liters with 1.375" ID port x 5" long gives Fb 68 Hz, F3/6/10 = 61/55/50 Hz
                        computer speakers so narrow baffle width 5" using 1/2" MDF, height 10 inches or so to keep drivers at ear level when seated at keyboard, depth about 6".

                        But now after learning from your posts above, I'm really liking the idea of making it smaller (3 liters) and using a slot port

                        I was lucky enough to pick up both drivers on sale (AXT-04 and the ND20FA-6) and am looking forward to learning from this build. I know that the ND20s aren't the fanciest tweeters, but when looking at designs like the Quarks, it appears that they can be tamed and made to sing quite nicely.


                        I think the ND20 will work well for you. I certainly never disliked the ND20 in the Quarks.
                        It's very flat, and pretty revealing. Not a lot to criticize.

                        Do you have a pair of Quarks? I've got a bunch of the FE-83 drivers on the shelf and
                        "might could" ( as they say in the South) take care of you if wanted.

                        It's still early on box design, but It's "gelling" around the 4th model, and I've got some cool
                        ideas for physical design. Gotta make sure that I can build it though.

                        Sketchup physical models coming next unless someone has a better alignment idea.

                        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


                        • #13
                          Originally posted by donradick View Post


                          I"m using the Quarks as my guide.
                          I used them for a long time as Desktop/Computer speakers, and even used them for a while full range for my HTR front L+R mains
                          and really didn't notice any distress at "normal" listening levels. Now that I've measured a whole bunch of speakers, I know that
                          90dB is quite loud, and I don't plan on running these that loud.

                          I wasn't comfortable in the first model with xmax exceeded at 57 Hz - lots of music in that area.
                          I'm much more comfortable with the 4th model, xmax exceeded at 43 Hz.

                          We shall see, but I feel pretty good about the final model.

                          That's what I thought you'ld say,, not a lot of music below 40 Hz. And the HTR may have a HP on the mains (maybe explicit or hidden in the form of the "small speaker" parameter.

                          Comment


                          • #14
                            Been looking at tweeters, taking my esteemed colleague Johny's advice, no one willl be using a ND20 tweeter with this driver.

                            Put the AXT-04s in some test boxes today and broke them in a little.
                            My wife came in and immediately noticed a much better quality of sound than usual.
                            Bass is not shabby either, even in a small sealed box.

                            Ok, back to tweeter selection.
                            Honestly, if the RS28 was still available, I'd use those and be done with it.

                            But, I'd like to keep this tweeter about $30--35 if possible.
                            If there is a great AMT at that price I'd like to try it, but for 1 inch domes, I'm leaning
                            towards a mid-priced TB soft dome - 25-1933S

                            The only other top contender is the SB26TCN-4, which several people like.

                            My requirements are smooth, low distortion, moderate low Fs, at least moderate to good detail.


                            Any other suggestions?


                            Tang Band 25-1933S 1" Fabric Dome Shielded Tweeter

                            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


                            • #15
                              Those are 2 excellent choices, you probably need to look no further. However, I really love the Dayton Audio AMT Mini-8 with a similar driver to the AXT-04, the DA PS95-8. Hard to make a wrong move among those 3, IMHO. Good luck and proceed. Watching with interest.

                              Comment

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