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  • #16
    Even w/the undersized box, adding a 3"id x 10" long vent (you can use/make an elbow to fit it in there) might add 10 more Hz to the bottom end. The port is undersized (dia.) which will tend to "chuff" more (at high volume) so I'd exit it out the back. The inner end of the port would best be placed up behind the 3" (so, NOT right behind the woofer).

    You can add that Zobel (resistor and cap - in series w/each other) across the woofer's terminals, for about $1 ! It will help the woofer roll off immensely.
    To help control the top end rise on the 3", add a (small) 0.10mH coil inline with the 10uF cap (can go before or after the cap - makes no difference).

    I'm about 90min from you (Appleton). I'd offer to measure these for you IF you can add the vent, the Zobel, and the small coil (inline w/the 3" to curb the top end. It would help if the XO was (temporarily) external - that way I could measure each driver individually, and the system as a whole). We could meet somewhere in the middle (like Waupun) for the "handoff" (twice) in about an hour. I'd want to have a few days to work with it (don't need/want both boxes).

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    • #17
      Originally posted by BikesAndRain View Post
      Hello! This is my first real speaker build and I was absolutely stoked to throw the drivers in and hear them for the first time yesterday. They still need veneering, but I couldn't wait to give them a try.

      They sound great to me, but I thought I'd ask if anyone had any advice in modifications or interpreting the frequency response. I do have some polyfill, and am planning on reinforcing the enclosure a little more on the sides. I also have a bunch of capacitors between 7 and 15 uF that I could swap out.


      Driver Specifications
      Woofer - Dayton Audio DC300-8 12" Classic Woofer
      Mid/Hi - Dayton Audio PC83-8 3" Full-Range Poly Cone Driver

      Enclosure
      Baffle, Top, Bottom 3/4" MDF, Sides, Back 1/2" MDF
      Mid Volume - 0.83 ft^3 CORRECTION 0.083 ft^3
      Woofer Volume - 1.34 ft^3

      Crossover
      First Order at 2000 Hz - 1.6 mH Inductor on the Woofer, 10 uF Cap on the Mid

      Measurement
      Measurements made in a 20x20ft room with a good amount of furniture, using REW and a Tascam DR-05 recorder positioned 1 yard away centered between woofer and mid.

      Thank you for looking!
      Kind of an unusual combination of drivers and enclosure. Beautiful cabinet work, but something like an 8 inch woofer would probably have worked better, that and a real tweeter. Save the 12" drivers for subwoofer duty.

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      • #18
        Chris - Thanks again! I'm mostly focusing on the low end right now, but when I get that sorted, I will definitely try out those crossover adjustments.

        AEIOU - Thanks. I incorrectly thought that a 12" could play low even in an undersized enclosure, but as you said, seems like an 8" would be more appropriate.

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        • #19
          Port Experiments Update

          I am somewhat apprehensive about cutting a large hole in my enclosure that I spent so much time on, so I figured I could use the terminal cup opening as a port and experiment around.

          The hole is about 3" by 2.25".

          I built a box "tube" with the same cross section as the terminal port that I could clamp to the back of the enclosure. I then took measurements and cut the tube shorter by 2" after each measurement.

          Results

          I was pretty surprised by the effect a small port had on the low end response - the best response was with only a stubby 2" section of the tube remaining!

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          • #20
            I'd have to say that that's fairly ingenious, still . . .
            you might have to play some music through them. Your goal here isn't just to maximize output (which SEEMs to be near 80Hz). A "boost" that's -20dB down (while visible on a plot) probably won't add much to overall enjoyment. Your closed box (in a box model) basically drops pretty fast below 60Hz. It peaks near 80Hz. I'd try to actually lower the 80Hz output seeking a gain in the 40-50Hz range.

            Veery, interesting.

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            • #21
              These are very cool speakers. I love the curved cabs and the idea. I’ve never seen that Dayton 3” before but it is very nice; good response and copper in the motor.

              If you follow Chris’ suggestions it will turn out very nice. If you take his generous offer to meet up to measure them, you will really have something! Those things could have some real potential.
              Projects:

              Breezy Monitors: http://techtalk.parts-express.com/fo...reezy-monitors
              transcenD: http://techtalk.parts-express.com/fo...5035-transcend
              Summits: http://techtalk.parts-express.com/sh...75-The-Summits
              References: http://techtalk.parts-express.com/sh...-My-References
              Vintage Style 2-way: http://techtalk.parts-express.com/sh...-vintage-2-way

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