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Tony Gee's Black Box / Big Cap on woofer in small box

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  • Tony Gee's Black Box / Big Cap on woofer in small box

    Has anyone built the Black Box? Or any comments about the "big cap on woofer to allow a smaller box" concept? Perhaps in another design?

    Thanks

  • #2
    https://sbacoustics.com/technical-notes/ CAPACITOR TUNING
    Attached Files
    Last edited by AEIOU; 07-11-2020, 09:31 AM.

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    • #3
      It's called a Passive Assist. It works with a higher Qts, the driver's Fs, and the Fc of the cap to facilitate bumping up the knee before rolloff in a 3rd order slope. Typically the driver should have a large Xmax, and a Qms between 7 and 10.

      Later,
      Wolf
      "Wolf, you shall now be known as "King of the Zip ties." -Pete00t
      "Wolf and speakers equivalent to Picasso and 'Blue'" -dantheman
      "He is a true ambassador for this forum and speaker DIY in general." -Ed Froste
      "We're all in this together, so keep your stick on the ice!" - Red Green aka Steve Smith

      *InDIYana event website*

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      http://techtalk.parts-express.com/blog.php?u=4102

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      • #4
        A worked example. This is an old Infinity 122.7W 12" car audio subwoofer in a 36 l box. A high-inductance woofer, it's a bit peaky at 56 Hz. Great for car audio I guess. Fb is at 40 Hz

        With 1000 uF of capacitance in series, the peak is tamed, and the response is extended down to 26 Hz. Hello, home audio subwoofer....

        Click image for larger version  Name:	20200710-1227W-cap.png Views:	0 Size:	64.4 KB ID:	1445833
        Last edited by Brian Steele; 07-11-2020, 05:09 PM.
        Brian Steele
        www.diysubwoofers.org

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        • #5
          With the price of a 1F cap being what it is I'd use DSP instead.
          www.billfitzmaurice.com
          www.billfitzmaurice.info/forum

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          • #6
            It's not so bad, Bill.

            If you use electrolytics(horrors!).

            Might need service in 30-50 years.

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            • #7
              When you can use DSP to not only remove the peak but also to totally tune the response to the room at a price no more than caps why use caps?
              www.billfitzmaurice.com
              www.billfitzmaurice.info/forum

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              • #8
                For minimum circuit involvement .
                I . E . More natural sound .
                Less solid state artifacts .

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                • #9
                  Originally posted by hitsware2 View Post
                  For minimum circuit involvement .
                  I . E . More natural sound .
                  Less solid state artifacts .
                  Big electrolytics aren't exactly artifact-free.
                  Francis

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                  • #10
                    More so than D.S.P.
                    ( Or even analog active Eq. )

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                    • #11
                      Originally posted by hitsware2 View Post
                      More so than D.S.P.
                      ( Or even analog active Eq. )
                      No. No, not for a long time at least. Good DSP these days has almost unmeasurable distortion.
                      Francis

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                      • #12
                        I don't know. Bill.....$15 for a channel of dsp and amplification is hard to reach in non-industrial quantities.

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                        • #13
                          Originally posted by billfitzmaurice View Post
                          When you can use DSP to not only remove the peak but also to totally tune the response to the room at a price no more than caps why use caps?
                          Exactly.

                          You can lead a horse to water......
                          Being defeated is often a temporary condition. Giving up is what makes it permanent.

                          Scanspeak Revelator R2904/7000's, Scanspeak Revelator 15M/4531K00's, Scanspeak Revelator 22W/8857T00's, Eminence NSW6021's.
                          MiniDSP 4x10HD. ICE Power amplification and an NX3000D.

                          Sennheiser HD650's powered by TEAC amplification.

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                          • #14
                            Unmeasurable does not mean inaudible .

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                            • #15
                              Originally posted by hitsware2 View Post
                              Unmeasurable does not mean inaudible .
                              OK, I'm outa here.
                              Francis

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