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Peerless MTMMM and MMTMMMM - 2.5 way designs

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  • Peerless MTMMM and MMTMMMM - 2.5 way designs

    Goals:
    - Cheap drivers (although crossover got a bit silly :-)
    - Drivers available in northern and southern hemisphere (no point having cheap drivers if shipping more than drivers)
    - Simple build - no router required - flush mounted drivers
    - Efficiency >= 89dB

    All the following is simulation only (including box, baffle step and baffle diffraction) based on traced FR graphs HBT generated phase and allowing for Z axis offsets for woofers.

    Looking to get feedback before finalising the "prototype" design before ordering parts.

    Drivers:
    Woofer - Peerless 830657
    Tweeter - Vifa DX25TG05-04 (aka Scan speak D2604-830000)

    Options:
    Design "A" - a 4 woofer MTMMM 2.5 way. Min impedance 3.6 ohms between 4KHz and 7Khz
    Design "B" - a 6 woofer MMTMMMM 2.5 way. Min impedance 3.0 ohms at 9KHz

    Enclosures
    Design A - 80L vented, tuned to 40 Hz, F3 = 54Hz, Max SPL 111dB. System sensitivity ~ 89 dB (including ~ 4 dB baffle step compensation)
    Design B - 120L vented, tuned to 40 Hz, F3 = 54Hz, Max SPL 114dB. System sensitivity ~ 92 dB (including ~ 4 dB baffle step compensation)

    The photos in this post are for design A

  • #2
    Design B:

    Comment


    • #3
      You might want to have an optic at the design Don Radick did for a similar project on PETT, which I think was six 830657 and a VIFA tweeter. Will post the link when I can find it.

      Geoff

      Comment


      • #4
        Originally posted by Geoff Millar View Post
        You might want to have an optic at the design Don Radick did for a similar project on PETT, which I think was six 830657 and a VIFA tweeter. Will post the link when I can find it.

        Geoff
        +1. I remember a similar build here.

        Comment


        • #5
          Cheers - yes I found it - the Trump Towers. I can't get the same response he got when modeling. Could be something I'm doing.

          Comment


          • #6
            Did you run a box model? To get low 40s (vented), I'm seeing over 2cf PER PAIR! A quad needs 4cf (too huge for most peeps), and six... would be even bigger.

            Comment


            • #7
              Originally posted by Dave Bullet View Post
              Cheers - yes I found it - the Trump Towers. I can't get the same response he got when modeling. Could be something I'm doing.
              Dave, I'm a little busy right now. IIRC, the Peerless I used had a VAS of about 20 liters, and I was determined to make 6 of them fit into a medium size tower.
              Ended up using a low tuned slot port, and heavily stuffing the box. They can really crank. PM me if you need some help.

              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


              • #8
                Originally posted by Chris Roemer View Post
                Did you run a box model? To get low 40s (vented), I'm seeing over 2cf PER PAIR! A quad needs 4cf (too huge for most peeps), and six... would be even bigger.
                Looks ok in a 120L vented enclosure as per below - dimensions - 51 H, 9 W, 22 D - not too big :-)

                Comment


                • #9
                  Originally posted by Dave Bullet View Post

                  Looks ok in a 120L vented enclosure as per below - dimensions - 51 H, 9 W, 22 D - not too big :-)
                  That looks great! What does excursion and port speed look like?

                  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
                    Excursion and port speed attached. This puts the output @ 114 dB max. Port is 12.7cm diameter (5 inches) and 10.43 cm long. Max speed < 16 m/s (should be ok?) I don't know if Jeff B's spreadsheet allows for a flared port (assuming no).

                    Attached a comparison of the 4 woofer and 6 woofer designs at 80 L and 120 L enclosure sizes. As you can see - the "big boy" is quite a bit deeper (over half a metre!) And you need to allow for a rear firing port - not shown in pictures (space from wall). So only big (i.e. deep) rooms need apply!

                    Comment


                    • #11
                      Even if you go w/6, I'd keep the MtM up top, w/a quad of woofers down below. Generally aim to keep the tweeter near seated "ear level" (if you'll be listening to these sitting down).
                      Personally, I'd maybe go w/4 in 100L. Else I'd miss the bottom end w/out a sub.

                      Comment


                      • #12
                        Originally posted by Chris Roemer View Post
                        Even if you go w/6, I'd keep the MtM up top, w/a quad of woofers down below. Generally aim to keep the tweeter near seated "ear level" (if you'll be listening to these sitting down).
                        Personally, I'd maybe go w/4 in 100L. Else I'd miss the bottom end w/out a sub.
                        I have quite a high sofa. My current 3 ways put the tweeter at 823mm from the ground which is exactly ear level. the 6 driver "B" model has the height at 842mm - so not far off.

                        I do agree you get another ~8 Hz (F3) extension going with the "A" model with 100L enclosure, vs. "B" model @ 120L. The optimum is 280L for the B (to get an F3 ~ 33Hz), but there's no way I'm going to get approval to build them 2.5 times bigger!

                        The plan for the 6 was to do
                        M (2.5 way)
                        M (2)
                        T
                        M (2)
                        M (2.5 way)
                        M (2.5 way)
                        M (2.5 way)

                        To maintain the upper mid Ms next to the tweeter.

                        I have no idea how nasty vertical lobing will be :-)
                        Last edited by Dave Bullet; 07-29-2018, 08:06 PM.

                        Comment


                        • #13
                          Port speed and excursion look good. You might try modeling with "heavy fill" and/or use a longer port, I found that both of those helped.
                          You can also safely model excursion using factory xmax + 15% = about 3.96 or 4.00 if you are me.

                          But the basic box model looks good at this point.

                          Um, one consideration - using a MMT up top means you will have to have some kind of 2.5 crossover there, or you will get combing.
                          You are right to keep the tweeter at ear level.


                          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


                          • #14
                            Originally posted by Dave Bullet View Post
                            Design B:
                            How about a wtmwww 3-way?

                            Comment


                            • #15
                              Originally posted by rpb View Post

                              How about a wtmwww 3-way?
                              With the same 830657? hmmmm good idea.

                              I'm worried my .5 isn't aggressive enough )ie. should be using a higher value inductor for a steeper drop off). I don't know if there is a rule of thumb in how much attenuation a .5 design should have to be considered a truue .5 design

                              Comment

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