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Modula NeoD CC build for fireplace mantel

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  • #16
    This is with the added mass method. Peak cone excursion is at 80 watts and 81hz when going for QTC of .707.
    Click image for larger version

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    • #17
      That looks much more reasonable. I assume that the 80Hz number is well below the red line at 45 degrees? If so, then you have a viable solution. If you start decreasing the box volume, then Qtc will go up. Basically, Frequency response will start to roll off pretty quickly below Fb. The higher the Qtc, the faster the rolloff. You will also start to see some ripple show up in the passband.

      https://en.wikipedia.org/wiki/Chebyshev_filter
      Welcome to Rivendell, Mr. Anderson.

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      • #18
        There isn't that much room but considering that it should be fine at regular listening levels, I am thinking it should be an ok size. At the same time, the measurements seem to be changing a bit as I run them and I may try to break them in a bit before completing the model.

        I am seeing a trend that most ported designs show over exclusion at lower levels. I assume these are not a concern due to the volume levels used and/or the recordings not going that low?
        Click image for larger version

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        • #19
          So, I think this is where it will land based on break-in. Vented has more extension and is tempting.
          Click image for larger version

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          • #20
            Your closed box model has the SPL intersect the Xmax curve right at 80Hz. Since most subwoofer crossover slopes are LR4 (-24dB/octave; -6 dB @ Fc), you should be just fine blasting your ears at 108dB.

            In the Vented model, you can clearly see what happens when the cone unloads below Fb. One either needs to be very cautious about content below ~40Hz (no explosions, no deep organ pipe music), or you are back to the subwoofer crossover. Since a Vented alignment is typically much larger than sealed, the additional extension only matters if you want to run full-range. There are opinions about what happens in the upper bass area for midwoofers designed to be vented but which are in closed boxes, but that's a discussion unto itself.
            Last edited by Bear; 16 August 2021, 09:51 Monday. Reason: grammar
            Welcome to Rivendell, Mr. Anderson.

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            • #21
              The vented modula MTM seems to have the same issue no? Or is there a frequency at which this is no longer a concern?
              Click image for larger version

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              • #22
                Take a look at something like the SW223BD02 in ~30L tuned to ~20 Hz. Or the L26ROY in about 50 - 60 liters. You'll see what the power handling looks like in a vented enclosure, but then look at the port resonance vs air speed for any given ID of vent. TANSTAAFL. That's why many of these subwoofers that can also be woofers do best with a PR alignment (e.g., SW223BD03 in 30L with a RSS265PR at 425g - 500g).
                Welcome to Rivendell, Mr. Anderson.

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                • #23
                  Crossover parts have been ordered. I will remeasure the drivers since I found an odd bug in the 3.11 version of DATS. One of my rs150-8 drivers was not responding to getting a FS measurement until I updated to 3.15.

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