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2-way MT: Dayton RS180S-8 and SEAS 27TDFC

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  • #16
    Re: 2-way MT: Dayton RS180S-8 and SEAS 27TDFC

    When I modeled that woofer in BassBox no matter what vented profile I tried there was a huge hump at cutoff. I wonder if the fs/qes of 85 is responsible, not really vented, not really sealed.


    Design Goals

    This design employs two cost-effective, low-distortion drive units, Dayton RS180S-8 and Seas 27TDFC (H1189), which have been popular and tested favorably by several well-known DIY'ers. The goal of this designing attempt was to develop a relatively simple crossover network that exploits the potential of the drivers in a 2-way.


    Crossover


    LR4 crossover at 1.6 kHz


    For this design, to suppress the high frequency breakup nodes of the metal cone driver, a bottomless LC notch filter, which is made of C2 and L3 in the above schematic, is used. This not only suppresses breakups but also contributes to low pass filtering of the woofer. In fact, a notch filter alone is not very effective in suppressing breakup nodes when applied to the RS180 since the woofer's breakup has two main peaks at 6 and 9 kHz. In this design, a low crossover frequency (1.6 kHz) through a large shunt capacitor (C2) and a notch filter centered in the middle of two breakups provide a good result.



    Predicted system response and individual driver rolloffs


    Plots of filter transfer functions and system impedance curve are attached below.


    Enclosure

    Net internal volume:
    For a vented option, 14 to 21 liters with 35 to 45 Hz port tuning.
    For example, Dayton 0.5 cu ft cabinet with PE 260-476 tube with no cutting;
    or Dayton 0.75 cu ft cabinet with 2" ID Precision Port cut to total 7".

    For a sealed option, 8 to 11 liters. Requires a subwoofer or two for full range reproduction.

    Baffle size:
    8" to 10" wide. Baffle height does not matter though it will somewhat affect midrange tonal balance.

    Driver layout on baffle:
    Tweeter's center is 3" from the baffle's top edge with 0.75" horizontal offset (L/R mirror image).
    Midwoofer's center is 5.75" below the horizontal line at which the tweeter's center is located.
    Drivers should be mounted flush with the baffle in recessed cutouts.


    Options

    Non-BSC, in-wall mount version is here (post yet to be added).


    Listening Impressions

    These are decent sounding speakers; way better than any commercial offerings under $500/pr I recently auditioned (mostly from Internet Direct loudspeaker companies). Voicing is near-perfect to my ear. The SEAS tweeter is really an excellent performer; it handles the design's low crossover requirement with aplomb. No wonder it's so popular. After trying various filter topologies, I really don't think this driver combination needs a more complex crossover.

    See another review here.

    [/QUOTE]

    Comment


    • #17
      Re: 2-way MT: Dayton RS180S-8 and SEAS 27TDFC

      Never mind, missing xmax and pe in the Bassbox database. Edited, normal now.

      Originally posted by clyde47 View Post
      When I modeled that woofer in BassBox no matter what vented profile I tried there was a huge hump at cutoff. I wonder if the fs/qes of 85 is responsible, not really vented, not really sealed.


      Design Goals

      This design employs two cost-effective, low-distortion drive units, Dayton RS180S-8 and Seas 27TDFC (H1189), which have been popular and tested favorably by several well-known DIY'ers. The goal of this designing attempt was to develop a relatively simple crossover network that exploits the potential of the drivers in a 2-way.


      Crossover


      LR4 crossover at 1.6 kHz


      For this design, to suppress the high frequency breakup nodes of the metal cone driver, a bottomless LC notch filter, which is made of C2 and L3 in the above schematic, is used. This not only suppresses breakups but also contributes to low pass filtering of the woofer. In fact, a notch filter alone is not very effective in suppressing breakup nodes when applied to the RS180 since the woofer's breakup has two main peaks at 6 and 9 kHz. In this design, a low crossover frequency (1.6 kHz) through a large shunt capacitor (C2) and a notch filter centered in the middle of two breakups provide a good result.



      Predicted system response and individual driver rolloffs


      Plots of filter transfer functions and system impedance curve are attached below.


      Enclosure

      Net internal volume:
      For a vented option, 14 to 21 liters with 35 to 45 Hz port tuning.
      For example, Dayton 0.5 cu ft cabinet with PE 260-476 tube with no cutting;
      or Dayton 0.75 cu ft cabinet with 2" ID Precision Port cut to total 7".

      For a sealed option, 8 to 11 liters. Requires a subwoofer or two for full range reproduction.

      Baffle size:
      8" to 10" wide. Baffle height does not matter though it will somewhat affect midrange tonal balance.

      Driver layout on baffle:
      Tweeter's center is 3" from the baffle's top edge with 0.75" horizontal offset (L/R mirror image).
      Midwoofer's center is 5.75" below the horizontal line at which the tweeter's center is located.
      Drivers should be mounted flush with the baffle in recessed cutouts.


      Options

      Non-BSC, in-wall mount version is here (post yet to be added).


      Listening Impressions

      These are decent sounding speakers; way better than any commercial offerings under $500/pr I recently auditioned (mostly from Internet Direct loudspeaker companies). Voicing is near-perfect to my ear. The SEAS tweeter is really an excellent performer; it handles the design's low crossover requirement with aplomb. No wonder it's so popular. After trying various filter topologies, I really don't think this driver combination needs a more complex crossover.

      See another review here.

      [/QUOTE]

      Comment

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