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It’s that time audio enthusiasts! Registration for the 2019 Speaker Design Competition is now open! Visit midwestaudiofest.com for details and to list your speaker project. We are excited to see all returning participants, and look forward to meeting some new designers this year, as well! Be sure your plans include a visit to the Parts Express Tent Sale for the lowest prices of the year, and the Audio Swap Meet where you can buy and trade with other audio fans. We hope to see you this summer! Vivian and Jill
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Bantams MTM Underway...

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  • Bantams MTM Underway...

    As soon as I heard the tiny "Bantams" handling demanding program material fairly loudly with no problem, I knew I wanted to explore the possibilities of an MTM version. I hadn't planned on working on it this soon, but DIY Indiana is coming up in April and the 3 Liter "Nano" theme this year seemed perfectly suited to an ND91 based MTM.

    Here is a front box drawing of what I envision:



    Side view of same:



    The design uses the same Dayton Audio AMTPOD tweeter... the one intended to go in a car: http://www.parts-express.com/dayton-...-pair--275-195

    Hey, I see they're only $35 on sale, nice!

    Woofer is the 8 ohm version of the ND-91: http://www.parts-express.com/dayton-...8-ohm--290-226

    ...and the passive radiators are the non-PE Peerless 5.25" passive radiators... a Mad deal at $12.75 There are two per cabinet opposing on the sides by the way.


    Here are a few shots of how construction as gone so far:










    The thin strips of solid wood are maple, and they will provide some additional backing material for screwing in the back panel. I need to have the back removable because I intend to do a solid hardwood baffle and I plan on fastening it from the rear, pulling it towards the cabinet. I may even rear-mount the woofers if I can pull it off.




    The maple corners and side thingy's are going to have oversized holes drilled in them to allow for some movement of the hardwood baffle as time goes on.



    As you can see from the initial sketches, I intend to round over the corners and base with probably a 3/4" roundover or so. Not sure on veneer or hardwood yet, I will have to take a closer look at what I have as time gets closer. I do now have a few pieces of decent wood to pick from, so that's nice.

    I want to try a 45 degree bevel on the front as I've never done that before and I think it will look nice and sharp with the hardwood front.

    So, internal volume is 2.9 liters not including any bracing, which there isn't any except the corner and side screw blocks. The original "Bantams" made do with about 1.2 liters, so the extra volume with the MTM version along with using two larger PR's should bring the F3 down to around 62 Hz or so... F6: 55 Hz, F10: 45 Hz. I'm anticipating these will have even more 'punch' in the bass region. Sometimes it's harder for smaller drives to have the same 'impact' as larger ones playing the same frequencies... hard to explain, but I think these will be even more satisfying to play loud.

    More to come...

    TomZ
    *Veneering curves, seams, using heat-lock iron on method *Trimming veneer & tips *Curved Sides glue-up video
    *Part 2 *Gluing multiple curved laminations of HDF *Cello's Speaker Project Page

    *Building the "Micro-B 2.1 Plate Amplifier -- Part 1 * Part 2 * Part 3 * Part 4 * * Part 5 'Review' * -- Assembly Instructions PDF

  • #2
    Looks like a great project, Tom.

    Comment


    • #3
      Very nice!
      I'm sure these will become a popular new standard.

      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
        Tom's turning into quite the mean mini-speaker machine!

        Comment


        • #5
          Very cool project.
          Can you share you box models. I'm curious about the tunning your getting from the ND91 with the PR.

          Also, is the frame on those ND91s similar to the ND140? They look thicker in the photos, but it could just be the perspective. I ask because, as everyone heard at the last DIY Chicago, I had some issues. I tightened the screws a bit too hard and warped the frame ever so slightly. It created the most fun air leak I've ever heard. On the deep bass passages, it sounded like someone was playing a trombone.
          - Ryan

          CJD Ochocinco ND140/BC25SC06 MTM & TM
          CJD Khanspires - A Dayton RS28/RS150/RS225 WMTMW
          CJD Khancenter - A Dayton RS28/RS150/RS180 WTMW Center
          CJD In-Khan-Neatos - A Dayton RS180/RS150/RS28 In/On Wall MTW

          Comment


          • #6
            I vote for rear mount with a hardwood baffle - love the front roundover in wood.

            Comment


            • #7
              Very neat build initiation, Tom! Just a note about pricing for those reading this, since you intend to compete...
              The driver prices to be used for the entries are to be non-sale prices, and PR's are included. Not saying you can't use on-sale items, just that the total price is to be calculated with daily retail pricing.

              Have fun! I bet those will be really cool!
              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


              • #8
                Tom, you do some bangin' work bruh. Keep it up. Love the design and the sexy standoffs.
                Builds - C-Killa - Speedsters - LithMTM - Talking Sticks - Pocket Rockets - Khanspires - Dayton RS Center - RS225/28A - Kairos - Adelphos - SEOS TD12X - Dayton 8 - Needles - 871S - eD6c - Overnight Sensations - Tritrix (ported) - Lineup F4 - Stentorians - The Cheapies - Tub Thumpers - Barbells - Tuba HT - Numerous subwoofers - probably missing a few...... :p

                Comment


                • #9
                  Originally posted by howard View Post
                  Looks like a great project, Tom.
                  ​Thanks Howard. I think the trick with making this one look special will be in what veneers/wood I use. Might need to ask the wife to get it right.

                  Originally posted by donradick View Post
                  Very nice!
                  I'm sure these will become a popular new standard.
                  ​Gracias!

                  Originally posted by Chris Roemer View Post
                  Tom's turning into quite the mean mini-speaker machine!
                  I gotta stop doing that, my fingers are far to fat for this stuff.

                  Originally posted by ---k--- View Post
                  Very cool project.
                  Can you share you box models. I'm curious about the tunning your getting from the ND91 with the PR.

                  Also, is the frame on those ND91s similar to the ND140? They look thicker in the photos, but it could just be the perspective. I ask because, as everyone heard at the last DIY Chicago, I had some issues. I tightened the screws a bit too hard and warped the frame ever so slightly. It created the most fun air leak I've ever heard. On the deep bass passages, it sounded like someone was playing a trombone.
                  ​Mr. K, here is a bit of information on that:

                  ​This design specifies heavy stuffing. Also, the PR's do not have any weight added. I tried adding and subtracting weight from these in my sim, but the stock weight was really the best.

                  ​I have not used the ND140's, but I have used the ND105's. I'm pretty sure the 91's and 105's at least are the same gauge metal - and possibly your 140's as well. It's great that PE gives us a gasket on these drivers pre-installed, but it's pretty thin, and on the 140's I can see where it would not be too hard to get an air leak due to the large screw-to-screw distance. I've done on one of my ND105's before, can be maddening! I actually made another gasket out of black craft foam for one of them that just didn't seem to want to sit right. I must have also bent the frame enough to keep it from sitting correctly.

                  Originally posted by Millstonemike View Post
                  I vote for rear mount with a hardwood baffle - love the front roundover in wood.
                  Thanks, me too. I'm going to try it if I have room with all the tweeters and woofers and things.

                  Originally posted by Wolf View Post
                  Very neat build initiation, Tom! Just a note about pricing for those reading this, since you intend to compete...
                  The driver prices to be used for the entries are to be non-sale prices, and PR's are included. Not saying you can't use on-sale items, just that the total price is to be calculated with daily retail pricing.

                  Have fun! I bet those will be really cool!
                  Wolf
                  ​Thanks for the clarifications. I assumed exactly what you stated, but it's nice to hear it for sure. I'm really looking forward to being part of the fun this year.

                  Originally posted by joeybutts View Post
                  Tom, you do some bangin' work bruh. Keep it up. Love the design and the sexy standoffs.
                  ​Thanks a lot. I hope I can stuff a couple of crossover bits in there at least!

                  TomZ
                  *Veneering curves, seams, using heat-lock iron on method *Trimming veneer & tips *Curved Sides glue-up video
                  *Part 2 *Gluing multiple curved laminations of HDF *Cello's Speaker Project Page

                  *Building the "Micro-B 2.1 Plate Amplifier -- Part 1 * Part 2 * Part 3 * Part 4 * * Part 5 'Review' * -- Assembly Instructions PDF

                  Comment


                  • #10
                    Crap, more stuff I would really like to see and hear going to Indiana! Cool concept and I bet they sound awesome for their size!
                    My "No-Name" CC Speaker
                    Kerry's "Silverbacks"
                    Ben's Synchaeta's for Mom
                    The Archers
                    Rick's "db" Desktop CBT Arrays
                    The Gandalf's

                    Comment


                    • #11
                      A "Mad deal", lol.

                      Comment


                      • #12
                        Originally posted by djg View Post
                        A "Mad deal", lol.
                        Hey, I drop a few Easter eggs in there from time to time...

                        TomZ
                        *Veneering curves, seams, using heat-lock iron on method *Trimming veneer & tips *Curved Sides glue-up video
                        *Part 2 *Gluing multiple curved laminations of HDF *Cello's Speaker Project Page

                        *Building the "Micro-B 2.1 Plate Amplifier -- Part 1 * Part 2 * Part 3 * Part 4 * * Part 5 'Review' * -- Assembly Instructions PDF

                        Comment


                        • #13
                          Tom,
                          Thanks for sharing the bass response model. It appears reasonable for the drive/box size. Though, I must admit I was wishing those PRs had more magic extension.

                          The frames on my ND140 is the same as my ND105. Sounds like the same as on the ND91. Which isn't a problem when used correctly.
                          - Ryan

                          CJD Ochocinco ND140/BC25SC06 MTM & TM
                          CJD Khanspires - A Dayton RS28/RS150/RS225 WMTMW
                          CJD Khancenter - A Dayton RS28/RS150/RS180 WTMW Center
                          CJD In-Khan-Neatos - A Dayton RS180/RS150/RS28 In/On Wall MTW

                          Comment


                          • #14
                            Why does the front baffle need to be removable?

                            Comment


                            • #15
                              Originally posted by ---k--- View Post
                              Tom,
                              Thanks for sharing the bass response model. It appears reasonable for the drive/box size. Though, I must admit I was wishing those PRs had more magic extension.

                              The frames on my ND140 is the same as my ND105. Sounds like the same as on the ND91. Which isn't a problem when used correctly.
                              Yeah, I was hoping for a tune in maybe the high 50's, but low 60's is about the best it's going to do in this iteration. More weight on the PR's extended the knee down to the mid 50 Hz range, but also dropped the total output from 50 to 70 Hz or so relative to the rest of the output. I don't think they could take much more weight as it is anyway, but at least I looked into it.

                              Why does the front baffle need to be removable?
                              It doesn't need to be really. Mostly, I'm just not in love with the idea of exposed screw/bolt heads on the front of the baffle. I've done that once and it's not as clean of a look as I like to have.
                              Plus if I rear-mount the woofers - which I'm likely to do - it will be a bit easier to get that done with the baffle removed.

                              It sure is a bit of extra work, though! And I'll have to be careful tightening the baffle or those little maple side thingy's are popping off!

                              And Kevin... it's only a 15 hour drive or so, right? I'm looking at over 10 hours myself. Sleep? who needs sleep?

                              TomZ
                              *Veneering curves, seams, using heat-lock iron on method *Trimming veneer & tips *Curved Sides glue-up video
                              *Part 2 *Gluing multiple curved laminations of HDF *Cello's Speaker Project Page

                              *Building the "Micro-B 2.1 Plate Amplifier -- Part 1 * Part 2 * Part 3 * Part 4 * * Part 5 'Review' * -- Assembly Instructions PDF

                              Comment

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