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  • Speedster MMTMM

    Looking for some help.

    I built the Speedsters a few years ago and am considering a center with the same drivers. While I've found a TMM design (and a build using the same crossover that was reordered into an MTM), I'm wondering if an MMTMM option is reasonable?

    I'm thinking of using the TMM crossover schematic, but with extra drivers in series.

    Thoughts?

    Thanks!



  • #2
    Adding more drivers or modifying the baffle would probably require a completely different crossover.

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    • #3
      What buggers said. Might sound good in the end, but you'll need to play with the crossover to get there.
      Francis

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      • #4
        The Speedster is a tiny speaker. Unless you need a super low profile center channel speaker, I'd just use one more TM Speedster for the center. The design has ample bass.

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        • #5
          You'll need to modify the crossover. With this configuration as a centre channel (laying on it's side I'm assuming) those two outer woofers should not play the same frequencies as the inner woofers as you will end up with really bad off axis response.

          Also if this is to match up with existing speedsters it's preferable to have them level matched. If you double up the woofers you'll have increase output from the centre that you'll have to try and level match with the mains through your receiver, if it has the capability. Probably not a big deal but just something to be aware of.
          Constructions: Dayton+SB 2-Way v1 | Dayton+SB 2-Way v2 | Fabios (SB Monitors)
          Refurbs: KLH 2 | Rega Ela Mk1

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          • #6
            Thank you for the replies. To be clear, the starting point of the crossover pictured above was not the speedster TM, but instead the speedster TMM. They’re already different crossovers.

            The circle is where I added the additional drivers in series.

            Thanks!

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            • #7
              You're doubling the load seen by the filter(s).
              To keep the same FR, you need to double-up any (coil) inductances and resistors, and halve all cap values.
              The high-pass (tweeter) is unaffected.

              This leaves you with (amp to drivers, or left to right):
              a 1.2mH series coil (w/twice the orig. DCR), then a shunt (to gnd) using a 2n(ohm) resistor and a 4uF cap,
              then a 0.40mH series coil followed by the 1st woofer(s) series string to ground, then the "extra" (large) coil
              of 4.0mH, and finally the 2nd (outer) woofer(s) series string to ground.

              Should work okay (and now you have an 8ohm nominal speaker).

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              • #8
                Thank you!

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                • #9
                  Originally posted by DeZZar View Post
                  ... With this configuration as a centre channel (laying on it's side I'm assuming) those two outer woofers should not play the same frequencies as the inner woofers as you will end up with really bad off axis response.
                  https://www.youtube.com/watch?v=GZrdsxrcpBw
                  " The Problem with Most Center Channel Speakers. (With Sound Demos & Data)"

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                  • #10
                    Originally posted by DrewsBrews View Post

                    https://www.youtube.com/watch?v=GZrdsxrcpBw
                    " The Problem with Most Center Channel Speakers. (With Sound Demos & Data)"
                    That’s a great link, thank you.

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