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Galeons - SB13 MTM

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  • Galeons - SB13 MTM

    (Named in honor of my favorite English ale - George Gale's Prize Old Ale)

    When I first heard about the SB Acoustics 5 ¼ inch mid-woofer for $19 I knew I had to try it. Good specs, very good frequency response, papyrus cone (!!) and of course that SB name.

    http://www.sbacoustics.com/index.php/products/oem-only/sb13pfc25-08

    I’ve heard that Meniscus is planning to stock this driver long term, but they are currently out of stock (June 2, 2013)

    After I listened to a single driver running full range in a ½ cube box, I figured they deserved a MTM design, with an eye to replacing my Maurbacs mains. Originally I had thought to use a nice Tangband soft dome, or one of the large face Vifa domes but I wanted to try a MTM with the drivers as close as possible, and I had 2 tweeters in a failed 3 way, so once again the venerable Vifa BC25SC06-04 was brought back.

    http://www.parts-express.com/pe/show...umber=264-1028


    I’d read some articles on Dual-Chamber-Reflex (DCR) alignments, and I wanted to try that also. Once I got the theory of design right (thanks guys!) – I modeled 2 woofers in Unibox (and WinISD) – 27 liters net, 2 ports, 2 inch inside diameter (SCH 40 PVC) that were each 6 inches long should give me an F3 of 42.5 Hz.

    Box internal dimensions 22H x 7 ¼W x 14D
    Local Home Depot had some “cabinet grade” ¾ ply that looked good, so I bought a few sheets. It did not disappoint! Faces were A/A to A/B, internal plys nice and even, and I never found a void.


    DCR theory says model for 2 ports, then use another port of the same length to join 2 chambers, one 2/3 of the volume, and the other 1/3 of the volume. I figured and planned, and still got it a bit wrong. I lined the insides with DOW 703 – really, really nice stuff.


    You can see a "brace: on the right one from front to back. Found out that it basically did nothing! I added some cross braces from side to side that helped a lot.
    Last edited by donradick; 06-03-2013, 05:35 PM. Reason: added title

    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
    Re: Galeons - SB13 MTM

    The SB13 drivers required an irregular shaped cutout. I used nottaway’s method:
    http://techtalk.parts-express.com/sh...r-Shape-Driver
    It worked pretty good, but of course there were complications. I found that I had a really hard time lining up the template on the baffle, so I got some Lexan and cut an opening the same size as the driver and scribed the lines on it.

    Since I wanted the drivers as close as possible, I mounted the tweeter, covered it with a bit of TP and blue tape, and just cut the face of it when I cut the recess for for the woofer. Sort of “white-knuckle” and not to be recommended, but came out pretty good in the end.

    I got some flat cut cherry veneer from Tapease, and researched finishing. Several of the “masters” recommended General Finishes ARM-R-SEAL gel coat, but I wanted something a bit warmer. In the end, I’d heard about the tendency of cherry to blotch with stain, so I decided to just use only the gel coat. They came out really, really nice. About 7 coats and I figured I was done. Typical sub-standard camera work by me.
    https://lh4.googleusercontent.com/-N...rch-3coats.JPG

    Last edited by donradick; 06-03-2013, 06:00 PM. Reason: added content

    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
      Re: Galeons - SB13 MTM

      Crossover turned out to be a standard LR2 on the woofer, and 3rd order on the tweeter. Getting enough BSC on the woofers (3 dB) resulted in a .56mH inductor, suggesting that a single SB13 (8 ohm) would need about a 1.2mH coil.
      I decided to go low budget, and used a NPE on the woofer, and mylar caps on the tweeter. The final FR came out really, really nice – basically +- 1dB from 45 Hz to 9 KHz. Assuming that I spliced the Omnimic curves correctly, it shows the F3 point at 35Hz (!!).


      Measured reverse null about 30 dB:

      Off axis looks good also – pretty smooth - this is on axis, 10, 20, 30 and 45 degrees off axis.


      Seems like I always get questions like “I don’t have a router, can I surface-mount the drivers?” – so I decided to surface mount them and measure the difference. Really, not much difference – surface mount is red.


      Finished crossover




      Auguest 11, 2013 UPDATE:
      Looks like I forgot a 2 ohm resistor for the tweeter in the crossover schematic.
      Correct crossover picture uploaded
      Attached Files
      Last edited by donradick; 08-11-2013, 03:44 PM. Reason: crossover update

      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
        Re: Galeons - SB13 MTM

        That's some really nice looking plywood.

        रेतुर्न तो थे स्रोत
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        in war, victory . . . in peace, vigilance . . . in death, sacrifice.

        Comment


        • #5
          Re: Galeons - SB13 MTM

          Originally posted by greywarden View Post
          That's some really nice looking plywood.
          They probably have it at HD in FLA - reasonable price - about $38 a sheet IIRC

          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
            Re: Galeons - SB13 MTM

            Nice job Don! You are getting pretty good at this.

            How do they sound?
            Don't worry, if your parachute fails, you have the rest of your life to fix it.

            If we all did the things we are capable of doing, we would literally ASTOUND ourselves - Thomas A. Edison

            Some people collect stamps, Imelda Marcos collected shoes. I collect speakers.:D

            Comment


            • #7
              Re: Galeons - SB13 MTM

              very nice writeup Don. Did you find that using two of the sb13 helped you get a f3 od 35? i might have to get two more and do a mtm.
              " To me, the soundstage presentation is more about phase and distortion and less about size. However, when you talk about bass extension, there's no replacement for displacement". Tyger23. 4.2015

              Quote Originally Posted by hongrn. Oct 2014
              Do you realize that being an American is like winning the biggest jackpot ever??

              http://www.midwestaudioclub.com/spot...owell-simpson/
              http://s413.photobucket.com/albums/pp216/arlis/

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              • #8
                Re: Galeons - SB13 MTM

                Originally posted by thekorvers View Post
                Nice job Don! You are getting pretty good at this.

                How do they sound?
                Thanks! I am increasingly reluctant to "blow my horn" on my designs, but I would say these
                are very smooth, have a very wide soundstage, and play bass with real authority.

                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


                • #9
                  Re: Galeons - SB13 MTM

                  Originally posted by [email protected] View Post
                  very nice writeup Don. Did you find that using two of the sb13 helped you get a f3 od 35? i might have to get two more and do a mtm.
                  Well, according to the model, using 1 should get you there, but with a MTM, you can crank them up real nicely. I am really, really digging that nice paper sound.

                  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


                  • #10
                    Re: Galeons - SB13 MTM

                    Don...this is very cool. Do you have any subjective observations on the DCR alignment? Anything in particular that stands out as a positive or negative??

                    Just to satisfy my selfish curoisity, I'm wondering if you can determine if there is any midrange leakage from the ports. Since they are rear-mounted, is there any way you can do a quick and dirty sweep measurement??

                    Really good job on the overall build!! :applause:
                    Bryan K.

                    Midwest Audio Club

                    Speedster | Sub Attaché | The Wildeman | Sean's NLA Towers | COÜGAR, COUGAR II and COÜGAR JR | Triton | Lithium | J-Boom | Trym MLTL | Docere MLTL

                    Comment


                    • #11
                      Re: Galeons - SB13 MTM

                      I'm not Don, Bryan, but I feel it allows the driver a bit more Xmax protection by spreading the tunings out over a broader range.
                      It did wonders on the W3-517S1 project I built. That little 3" still only could take so much though...

                      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


                      • #12
                        Re: Galeons - SB13 MTM

                        Wow, might have to skip my Maurbacs build and go for these, hard to keep up lol. That low end extension is very attractive considering the same size foot print as the Maurbacs. Don, what are your thoughts in comparing the 2 speaker designs? I am looking for a set of garage speaker....

                        Comment


                        • #13
                          Re: Galeons - SB13 MTM

                          Nice work Don, This looks like a high-value, well-executed design with a thorough design write-up. I would be curious to hear them. I did a project a long time ago with some Def Tech buyout 5.25" woofers that helped give me a healthy appreciation for what a good paper cone driver can do in the mids.
                          Keep an open mind, but don't let your brain fall out.

                          Argon | Helium | Lithium | LithMTM | Hafnium
                          Mercury | Matrix | Shrubbery

                          Comment


                          • #14
                            Re: Galeons - SB13 MTM

                            I echo Scott's sentiments on this project, and would like to point out one of the advantages of an MTM with slightly shallower slopes - that off-axis in the horizontal performance is very nice, indeed.

                            FYI: I would have probably voiced mine closer to the surface mount curve
                            Don't listen to me - I have not sold any $150,000 speakers.

                            Comment


                            • #15
                              Re: Galeons - SB13 MTM

                              Originally posted by bkeane1259 View Post
                              Don...this is very cool. Do you have any subjective observations on the DCR alignment? Anything in particular that stands out as a positive or negative??

                              Just to satisfy my selfish curoisity, I'm wondering if you can determine if there is any midrange leakage from the ports. Since they are rear-mounted, is there any way you can do a quick and dirty sweep measurement??

                              Really good job on the overall build!! :applause:
                              Thanks Bryan - the DCR really helps to improve midrange clarity, especially when you crank 'em up. It's spooky to hear all this volume, and
                              the woofers are hardly moving. I do not notice the dip around 90Hz at all.
                              I'll be happy to run a sweep on the rear port - I do expect some midrange oout of it, since it's directly behind the 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

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