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RST28F in a Visaton waveguide

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  • #31
    Hey civit , I haven't done much more with this than what I posted on Dec 7th. I am planning to use this in an upcoming design, but definitely haven't put anything approaching a passive XO on here to take measurements yet. Xmax may have some more details. I think he's played with this a bit in his shop.
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    • #32
      Originally posted by KEtheredge87 View Post

      hmm... that's an interesting question. I have never done any work with waveguides before this, but I think no sealant would be required based on my thoughts... By way of example, if you disassemble the tweeter, you'll see the RST28 itself is a stacked assembly consisting of the magnet / body, the dome carrier with voice coil and hook-up tabs, the wire mesh grille, and the large aluminum mounting flange. The only thing that is even a slight gasket in that stack is a little bit of material between the dome carrier and the magnet / body. If I were not putting this tweeter in a waveguide, I wouldn't have opened it up to put more gasketing between the dome and the grille / mounting flange. This waveguide mounting arrangement also has a flat surface pressed against the dome carrier, so in my mind the joint is maintained in the same fashion.

      For what it's worth - I will also be using this in a vented cabinet arrangement when I get around to it. A miniscule leak around the tweeter dome will be nearly impossible to detect in the frequency response. Even if I were using it in a sealed cabinet arrangement, many woofers like the dayton reference series have a vented pole piece and a phase cone which would allow some air to breathe in and out of the cabinet. I don't believe it's enough to throw off any acoustic suspension (sealed cabinet) alignments.

      All in all, I wouldn't do it. If others disagree with me, I'm happy to hear from others with some real experience.
      I had issues with a home made waveguide. The seal between the waveguide and dome tweeter, or possibly the waveguide to box seal. It would occasionally squeak from air being pushed past the seal. It was easy to hear when it occurred. If I was making one now, I think I would make a small chamber to isolate the whole tweeter / waveguide assembly. Like a mid chamber.

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      • #33
        Originally posted by rpb View Post

        I had issues with a home made waveguide. The seal between the waveguide and dome tweeter, or possibly the waveguide to box seal. It would occasionally squeak from air being pushed past the seal. It was easy to hear when it occurred. If I was making one now, I think I would make a small chamber to isolate the whole tweeter / waveguide assembly. Like a mid chamber.
        The mid-chamber idea makes a lot of sense... an easy way to avoid pressurization and squeaks if they're going to happen! I'll keep that one in mind. Thanks rpb.
        Voxel Down Firing with Dayton SA70
        Translam Subwoofers - The Jedi Mind Tricks
        The Super Bees - Garage 2 way
        SevenSixTwo - InDIYana 2018 Coax
        The Defiants - InDIYana 2019 "Bare Minimum" Build

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        • #34
          Originally posted by KEtheredge87 View Post

          The mid-chamber idea makes a lot of sense... an easy way to avoid pressurization and squeaks if they're going to happen! I'll keep that one in mind. Thanks rpb.
          Surely it would be easier to produce a viable gasket between the faceplate and waveguide? I have access to laser cutters; it may make sense to just do that.

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          • #35
            I think that depends on how thick your gasket material is... I know that getting the dome into the WG throat is important, so as long as you aren't causing your dome to sit too far back, it's probably OK. Response Measurements would help clarify how far back is too far. Sent from my Pixel 2 XL using Tapatalk
            Voxel Down Firing with Dayton SA70
            Translam Subwoofers - The Jedi Mind Tricks
            The Super Bees - Garage 2 way
            SevenSixTwo - InDIYana 2018 Coax
            The Defiants - InDIYana 2019 "Bare Minimum" Build

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            • #36
              Originally posted by KEtheredge87 View Post
              I think that depends on how thick your gasket material is... I know that getting the dome into the WG throat is important, so as long as you aren't causing your dome to sit too far back, it's probably OK. Response Measurements would help clarify how far back is too far. Sent from my Pixel 2 XL using Tapatalk
              I'd cut a disc out of compressible 1/16th inch neoprene foam. Similar to what is used as a gasket on some driver frames. I don't think you'd need much - it's not like there's a gasket anywhere in the normal tweeter assembly, although the grille retaining piece might have some give to it.

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              • #37
                Originally posted by civit View Post
                I cut a disc out of compressible 1/16th inch neoprene foam. Similar to what is used as a gasket on some driver frames.
                Nice! I'd love to see some pictures when you can. Sent from my Pixel 2 XL using Tapatalk
                Voxel Down Firing with Dayton SA70
                Translam Subwoofers - The Jedi Mind Tricks
                The Super Bees - Garage 2 way
                SevenSixTwo - InDIYana 2018 Coax
                The Defiants - InDIYana 2019 "Bare Minimum" Build

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                • #38
                  I just ordered an RST28f and a DX25BG60-04 (the big dual magnet looking unit from vifa/peerless/scan speak classic). Audioexcite loaded this one in the monacor waveguide with excellent results. Will do some measurements when I get them.

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                  • #39
                    If you plan to use the DX25BG60... or ...30 without the face plate, you will need to turn or mill the back of the guide to accommodate the tweeter body. This is worth the effort though. In my experience both of these ring radiators produce pleasantly impressive sound in waveguides. The only better sounding tweeter in a wg, as I recently found is the TB 25-1372SC, which is outstanding. I hope you will listen as well as test.

                    Below is a link to photos of the back of a guide and tweeter less the face plate.

                    https://flic.kr/p/28cicH3

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                    • #40
                      Originally posted by TN Allen View Post
                      If you plan to use the DX25BG60... or ...30 without the face plate, you will need to turn or mill the back of the guide to accommodate the tweeter body. This is worth the effort though. In my experience both of these ring radiators produce pleasantly impressive sound in waveguides. The only better sounding tweeter in a wg, as I recently found is the TB 25-1372SC, which is outstanding. I hope you will listen as well as test.

                      Below is a link to photos of the back of a guide and tweeter less the face plate.

                      https://flic.kr/p/28cicH3
                      That looks like a hassle. I have access to some machine tools but I'd like to keep it simple...Heissman acoustics online mated it to the monacor waveguide without too much trouble so I assumed I could too.

                      https://heissmann-acoustics.de/en/cnc-adapterplatte/


                      I see the issue now that you mention it. When I have them in hand I'll see if it's a simple matter of making an adapter or if waveguide modification is needed, hopefully the latter.

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                      • #41
                        If you want to send me the guide so I can measure it, I can make you an adapter. I have done similar things for other forum members and don't charge in order to promote research. I am interested in your test results and listening impressions. I might also post a .stl file for others to print their own adapters, although, there is also a .stl file in the writeup you linked.

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                        • #42
                          The guide throat dia. here is 38mm, or 1.496", as I recall the surround dia. on the ring radiator is 1.525". Click image for larger version

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                          • #43
                            Originally posted by TN Allen View Post
                            The guide throat dia. here is 38mm, or 1.496", as I recall the surround dia. on the ring radiator is 1.525". Click image for larger version

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                            TN I may just take you up on that. When I get the waveguide I will take more accurate measurements and make a model in Rhino and send you an STL or DXF or whatever format you prefer. The faceplate of the tweeter would need to be characterized too.

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                            • #44
                              OK. I should have Rhino soon, otherwise an IGES file may be better. Importing .stl files as a surface or solid is time consuming. I may have a guide with the correct mounting configuration, if you want to try another contour.

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                              • #45
                                Originally posted by TN Allen View Post
                                The guide throat dia. here is 38mm, or 1.496", as I recall the surround dia. on the ring radiator is 1.525".[/ATTACH]
                                It didn't occur to me that the DX25 surround diameter was so wide given it's a 25mm dome. I will check it when I get it. Perhaps we can try another small dome; some of the new SB acoustics models might be ideal.

                                Keep in mind the writeup I linked from Heissman acoustics is for another waveguide; one produced by Monacor, which has a throat which extends past the mounting plate.

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