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It’s that time audio enthusiasts! Registration for the 2019 Speaker Design Competition is now open! Visit midwestaudiofest.com for details and to list your speaker project. We are excited to see all returning participants, and look forward to meeting some new designers this year, as well! Be sure your plans include a visit to the Parts Express Tent Sale for the lowest prices of the year, and the Audio Swap Meet where you can buy and trade with other audio fans. We hope to see you this summer! Vivian and Jill
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Another small subwoofer with W6-1139SIF

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  • #16
    Originally posted by Brian Steele View Post

    THD will vary not only with frequency, but the SPL level the subwoofer is producing. Test it at different output levels to see how the THD varies, and how the frequency response varies as well. It's easy to very the test signal level in REW in 1dB or 3dB steps in order to take these measurements.
    OK, I was overthinking your comment. It makes sense. Am I correct that all these types of measurements should be done with the mic about 1 cm away from the driver? That is how I did the previous readings.

    I've also played around with the in room measurements (mic turned up 90 degree at the listening position) and I am get a large rise at approximately 40Hz. I'm still trying to figure out if I am doing this correctly.

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    • #17
      It might be difficult to do THD tests at different output levels with the mic so close, as the mic may get overloaded. Measuring from about 1M outside should reduce room effects.
      Brian Steele
      www.diysubwoofers.org

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      • #18
        Looks good! Hows it sound sealed?

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        • #19
          Originally posted by tkundhi View Post
          This was primarily a learning exercise for design and woodworking. I need a small subwoofer to pair with a set B&W M-1s. The M1s will be replaced with something I build in the near future. But space for the sub is very limited. This setup is used for music but not critical listening. No home theater. I'm thinking I may build a Voxel or another proven design to compare.

          Overall I'm pleased with the result. I would do a couple things differently next time. Like, routing a recess for the plate amp so it sits flush. For the finish I tried a vinyl made in Germany. It took 2 tries to get it right. In the end it turned out OK. It was a challenge to get the edges to look professional. I'm new woodworking so I wasn't ready to attempt veneer.

          Tang Band W6-1139SIF
          Yung SD100-6
          Modeled F3 @ 40Hz
          9 inch cube constructed from 3/4" MDF
          d-c-fix 346-8007 Decorative Self-Adhesive Film, Blackwood
          no fill or lining
          Nice sub, but I don't understand how you get f3 40 hz in a 7 liter sealed enclosure. Even in a ported 7 liter enclosure it is just possible to get that responce. Do you used bass boost or am I see it wrong.
          ​​​​​​
          Greetz

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          • #20
            Yung "SD100" = no boost
            "SD100-6" = +6dB boost

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            • #21
              That explain it. Thanks Chris! A question in my mind...a sealed speaker will have a decrease of 3 db. Does this mean the xmax will also decrease. If it's that way you can make a sealed enclosure that play as loud as ported, it will only need more power.

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              • #22
                Originally posted by Scarface1 View Post

                Nice sub, but I don't understand how you get f3 40 hz in a 7 liter sealed enclosure. Even in a ported 7 liter enclosure it is just possible to get that responce. Do you used bass boost or am I see it wrong.
                ​​​​​​
                Greetz
                Sorry for the delayed reply. Lots of work travel since April. Yes, bass boost as Chris stated. I'm hoping to do some more measurements soon. All the travel time allowed me to do a fair bit of reading on measurements.

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