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  • Re: The Bloom

    Originally posted by Skywave-Rider View Post
    More proof diffraction off of the baffle edge affects both woofers and tweeters. In this case, the woofer especially. (Move those KDT baffles forward guys.) The directivity is getting so progressive and smooth throughout the frequency range... what remains to be done?
    Flush-mounting the waveguide and rounding over the edges themselves. I believe we have incrementally demonstrated that while commonly known "best practice" may only minimally affect on-axis response of waveguide designs, its value in achieving smooth power response is clear -- getting the directivity "right" is fundamental....



    Originally posted by Zilch View Post
    I'm not ready to throw in the towel quite yet. ;)
    Attached Files
    Last edited by Zilch; 09-16-2010, 06:00 PM.

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    • Re: Flex Your PCD Mettle:

      Originally posted by Skywave-Rider View Post
      Oh...verticals.
      http://techtalk.parts-express.com/sh...27#post1669327

      It dropped below 4 Ohms at 5.2 kHz and ended up at 3 Ohms at 20 kHz.

      I've since reworked it, and here is the measured result in comparison:



      It just took an additional resistor and some component value tweaks to keep it above 8 Ohms across the entire spectrum. I'm gonna try to move the forward axis down a couple of degrees before calling it a "wrap." Extra effort with these old Altec midwoofs, 'cause they're sounding mighty tasty....

      Footnote: 16-Ohm 4555s and diaphragms are available; I just don't have any.
      Attached Files
      Last edited by Zilch; 09-17-2010, 04:45 AM.

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      • Re: Flex Your PCD Mettle:

        Interesting Zilch,
        Availability being what it is on the altec, are there any other candidates for mid-woofer that you would recommend?
        Regards,
        Dan

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        • Altec

          I recently called in to GPA for prices on new Altec (GPA) 414 woofers:
          Pricing from GPA minus shipping:
          414 Alnico: $330.
          414 Ceramic: $240.
          Both 8 or 16 Ohm.
          http://www.nytimes.com/2010/10/14/bu...html?src=busln

          http://mixonline.com/mag/audio_new_york_metro_46/

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          • Re: Flex Your PCD Mettle:

            Originally posted by NEO Dan View Post
            Interesting Zilch,
            Availability being what it is on the altec, are there any other candidates for mid-woofer that you would recommend?
            Vintage alnico ones like the ones I'm using here seem to be going for ~$300/pair. Altec made both consumer and pro products with pairs in them and 811B horns. There was even a HeathKit clone. These are not rare woofers.

            I'm not suggesting stripping them, rather, merely observing that there is ongoing availability from those who do that. GPA can also recone damaged ones.

            We've worked through several options already in this thread, and there are plenty more to try. Let's not ignore the vintage EconoWave candidates, if that's our pleasure, is all; PCD can coax even difficult combinations such as this one to happen....

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            • Re: The Bloom

              [QUOTE=Zilch;1672274]Is all but gone after moving the baffle flush front:



              Beautiful polar.

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              • Re: The Bloom

                Originally posted by bruson View Post
                Beautiful polar.
                The speaker itself is somewhat of a work of art at this point.

                [I ain't sayin' what "movement," tho.... :D ]

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                • Re: Flex Your PCD Mettle:



                  Still a work in progress.

                  Used the 1 cu ft PE sub box on sale for the 10" B&C 10PS26.

                  This fall I'll do some measuring for the xover and pretend I'm Zilch (HA!)

                  Xover is now a simple LR around 1200hz.
                  Sounds good but I expect some measurements will improve that this fall.

                  I routed a 1/2" roundover on the box and I'm back to using the 3" yellow swim noodle for the WG roundover, not pictured.

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                  • Re: Flex Your PCD Mettle:

                    I've linked your project in the first post and uploaded your pics here so they don't get lost if they're deleted from PhotoBucket, including your earlier version:

                    http://techtalk.parts-express.com/sh...94#post1663194
                    Attached Files

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                    • Re: Flex Your PCD Mettle:

                      OK I'm giving PCD a try and I would appreciate any tips. I am using a 15" woofer with the D220ti on a QSC waveguide. My vertical C-C spacing is 12" and WG is 3/4" forward of the 15. I don't quite know how to set the offsets in PCD. the modeled response does closely match the measured so wegot something right.
                      The crossover I'm working with currently is the ewave SR variant minus the LCR notch on the woofer. I have a small bump in the crossover region I would like to improve. all measurements are on axis @1meter.
                      Attached Files

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                      • Re: Flex Your PCD Mettle:

                        The pic.
                        Attached Files

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                        • Comment


                          • Re: Flex Your PCD Mettle:

                            Originally posted by bkillen View Post
                            The pic.
                            That's gonna work, looks like. Get the system up off the floor for your measurements. As you see in the ZilchLab pics, I have the mic and axis of device under test at ~1/2 ceiling height to minimize reflections from the floor and ceiling, and a similar distance away from other objects and boundaries in the space. For convenience, that means inverting the speaker on my relatively high test stand, and thinking "upside down."

                            From my own experience, you have too much overlap of the drivers in the crossover region. Look back at the final crossover design plots of the projects completed earlier in this thread to get more of a feel for this.

                            Since you have a wider center-to-center distance using a 15" driver than I typically show with 12s (10.5"), aim for the lowest crossover frequency that'll work to maximize the usable height of the forward lobe. That suggests moving your lowpass successively downward, or increasing its rolloff slope, leaving your highpass where it presently is for starters; the response hump in the crossover region should disappear when you have it "right."

                            Pete and others may have additional suggestions....

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                            • Re: Flex Your PCD Mettle:

                              Thanks for those concise, clear posts, Zilch.

                              Sorry, no "thumbsup" emoticon here on Techtalk.
                              http://www.nytimes.com/2010/10/14/bu...html?src=busln

                              http://mixonline.com/mag/audio_new_york_metro_46/

                              Comment


                              • Re: Flex Your PCD Mettle:

                                Originally posted by Skywave-Rider View Post
                                Thanks for those concise, clear posts, Zilch.
                                Yea, What he said.

                                thanks, that clarifies a lot, I will let everyone know how it comes out.
                                Last edited by bkillen; 09-29-2010, 06:11 PM. Reason: fixed quote

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