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Flex Your PCD Mettle:

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  • #16
    Re: Flex Your PCD Mettle:

    Well, I reset the targets and took another shot at it. I still have more components than you, mainly to take care of that resonance and give the woofer a smoother roll off. 4 on the woofer, 5 on the tweeter to do some shaping as well.[/IMG]
    We are very close, and have arrived at the same topology, looks like, as I'm 5 on the tweeter, not 4. I have PM'd you my values.

    The speaker is upside-down in the pic for convenience in measuring, though it should work either way. When I said forward axis "above" the midpoint between drivers, I meant between there and the waveguide, actually. Sorry for that confusion.

    Interestingly, there's a current thread about speakers for a HS bandroom. In that installation, they'd be mounted as in the pic, up high, with the forward axis aimed slightly downward.

    http://techtalk.parts-express.com/sh...d.php?t=215547

    If we can tame it, DC300-8 appears to be a capable low-cost performer:

    http://techtalk.parts-express.com/sh...34#post1600434

    Comment


    • #17
      Re: Flex Your PCD Mettle:

      Originally posted by Zilch View Post
      We are very close, and have arrived at the same topology, looks like, as I'm 5 on the tweeter, not 4. I have PM'd you my values.

      The speaker is upside-down in the pic for convenience in measuring, though it should work either way. When I said forward axis "above" the midpoint between drivers, I meant between there and the waveguide, actually. Sorry for that confusion.

      Interestingly, there's a current thread about speakers for a HS bandroom. In that installation, they'd be mounted as in the pic, up high, with the forward axis aimed slightly downward.

      http://techtalk.parts-express.com/sh...d.php?t=215547

      If we can tame it, DC300-8 appears to be a capable low-cost performer:

      http://techtalk.parts-express.com/sh...34#post1600434
      Why not go for the gusto and use a 12" pro woofer? This beast can handle the range nicely, and it's 6dB more sensitive. :D

      R = h/(2*pi*m*c) and don't you forget it! || Periodic Table as redrawn by Marshall Freerks and Ignatius Schumacher || King Crimson Radio

      Byzantium Project & Build Thread || MiniByzy Build Thread || 3 x Peerless 850439 HDS 3-way || 8" 2-way - RS28A/B&C8BG51


      95% of Climate Models Agree: The Observations Must be Wrong
      "Gravitational systems are the ashes of prior electrical systems.". - Hannes Alfven, Nobel Laureate, Plasma physicist.

      Comment


      • #18
        Re: Flex Your PCD Mettle:

        Why not go for the gusto and use a 12" pro woofer? This beast can handle the range nicely, and it's 6dB more sensitive. :D
        I have Kappalite 3012LFs coming for another variant. Is that what you're showing above?

        With assist, those'll do 114 dB @ 30 Hz in these cabs.

        [Better use Gorilla Glue to build 'em tho.... :p ]

        Comment


        • #19
          Re: Flex Your PCD Mettle:

          Augerpro's measurements of this waveguide are posted here:

          http://sites.google.com/site/driverv...-jbl-knock-off

          The polars were taken using DE250 and a throat adapter with no highpass filter:

          Horizontal:

          http://493531664873718246-a-18027447...attredirects=0

          Vertical:

          http://493531664873718246-a-18027447...attredirects=0

          It's beginning to lose vertical pattern control at 3 kHz, still usable at 2 kHz, but below that, we're relying upon the vertical nulls to augment the pattern per the teachings of Pi-Speakers' Wayne Parham. The horizontals reach nearly an octave lower with equivalent control. Load in separate tabs and click between them to view the difference in directivity....

          Comment


          • #20
            Here's mine:









            Attached Files
            Last edited by Zilch; 02-01-2010, 08:17 PM.

            Comment


            • #21
              Driver Alignments in KD Trap Cab:

              DC300 rear mount & D2500Ti on standard eWaveguide front mounted:



              Kappalite 3012LF rear mount & DE250 on QSC waveguide front mounted:


              [Please excuse the dust.... ;) ]
              Attached Files

              Comment


              • #22
                Flex It, Round Two:

                KappaLite 3012LF and B&C DE250 on QSC 152i waveguide:


                I have provided an FRD of both drivers concurrently from the midpoint between them (10.5" c/c distance) for finding the acoustic offsets per the method of Ralph:

                http://www.speakerdesign.net/sbarticle.html

                See driver alignment pic in previous post.

                What I've got:





                Attached Files
                Last edited by Zilch; 02-26-2010, 01:51 AM.

                Comment


                • #23
                  Re: Flex It, Round Two:

                  Originally posted by Zilch View Post
                  KappaLite 3012LF and DE250 on QSC 152i waveguide:


                  I have provided an FRD of both drivers concurrently from the midpoint between them (10.5" c/c distance) for finding the acoustic offsets per the method of Ralph:

                  http://www.speakerdesign.net/sbarticle.html

                  See driver alignment pic in previous post.

                  What I've got:





                  Looks a little "hot" around 1-2KHz. Can you begin the tweeter roll off just a tad sooner to help bring down that peaking?
                  R = h/(2*pi*m*c) and don't you forget it! || Periodic Table as redrawn by Marshall Freerks and Ignatius Schumacher || King Crimson Radio

                  Byzantium Project & Build Thread || MiniByzy Build Thread || 3 x Peerless 850439 HDS 3-way || 8" 2-way - RS28A/B&C8BG51


                  95% of Climate Models Agree: The Observations Must be Wrong
                  "Gravitational systems are the ashes of prior electrical systems.". - Hannes Alfven, Nobel Laureate, Plasma physicist.

                  Comment


                  • #24

                    http://www.avsforum.com/avs-vb/showt...3#post18127203

                    The wavelength at 1.5 kHz is 9.04" by my calc, so we're operating in the region between 1 and 1.5 lambda there....
                    Attached Files

                    Comment


                    • #25
                      Re: Flex Your PCD Mettle:

                      Regenerated FRDs from one axis, midpoint between the woofer and waveguide, @ 44" measuring distance.

                      [WHAT, no dancing banana...? :p ]
                      Attached Files

                      Comment


                      • #26
                        Re: Flex Your PCD Mettle:

                        Reworking the crossover from the new data, I was able to eliminate a couple of parts, but it still has some excess energy at 2 kHz:


                        Key to the vertical polar map:

                        Red = Forward Axis
                        Up toward waveguide = Org, Yel, Gry, Lt. Gry
                        Down toward woofer = Grn, Blu, Vio, Cyn
                        Attached Files

                        Comment


                        • #27
                          Re: Flex Your PCD Mettle:

                          Originally posted by Zilch View Post
                          Reworking the crossover from the new data, I was able to eliminate a couple of parts, but it still has some excess energy at 2 kHz:

                          I'd like to play with them. Do your FRD files already include relative acoustic offset?
                          R = h/(2*pi*m*c) and don't you forget it! || Periodic Table as redrawn by Marshall Freerks and Ignatius Schumacher || King Crimson Radio

                          Byzantium Project & Build Thread || MiniByzy Build Thread || 3 x Peerless 850439 HDS 3-way || 8" 2-way - RS28A/B&C8BG51


                          95% of Climate Models Agree: The Observations Must be Wrong
                          "Gravitational systems are the ashes of prior electrical systems.". - Hannes Alfven, Nobel Laureate, Plasma physicist.

                          Comment


                          • #28
                            Re: Flex Your PCD Mettle:

                            I'd like to play with them. Do your FRD files already include relative acoustic offset?
                            The new set of FRDs was taken from a single point in space, at the midpoint between the drivers and on axis horizontally, so the responses would include the relative offsets.

                            They include minimum phase. I don't know how CLIO calcs that, but I did not alter the time window.

                            I also provided the same measurement for the two drivers combined, from which the relative offsets may be derived by matching the response with no filters.

                            I did that, and came up with a crossover having a beautiful response curve and phase behavior. I built it up, measured the response, and it had a perfect inverse notch at the design axis, which I take to mean that the correct offsets should be derived with the HF polarity inverted.... :p

                            Comment


                            • #29
                              Re: Flex Your PCD Mettle:

                              Originally posted by Zilch View Post
                              The new set of FRDs was taken from a single point in space, at the midpoint between the drivers and on the horizontal axis, so the responses would include the relative offsets.

                              They include minimum phase. I don't know how CLIO calcs that, but I did not alter the time window.

                              I also provided the same measurement for the two drivers combined, from which the relative offsets may be derived by matching the response with no filters.

                              I did that, and came up with a crossover having a beautiful response curve and phase behavior. I built it up, measured the response, and it had a perfect inverse notch at the design axis, which I take to mean that the correct offsets should be derived with the HF polarity inverted.... :p
                              If it includes minimum phase, then relative offsets are not included, but could be derived by adjusting the individual offsets until the summed response matches the measured combined response. From what I can see, the tweeter is behind the woofer about 2.5" in order to get the result you measured for the raw combined response.
                              R = h/(2*pi*m*c) and don't you forget it! || Periodic Table as redrawn by Marshall Freerks and Ignatius Schumacher || King Crimson Radio

                              Byzantium Project & Build Thread || MiniByzy Build Thread || 3 x Peerless 850439 HDS 3-way || 8" 2-way - RS28A/B&C8BG51


                              95% of Climate Models Agree: The Observations Must be Wrong
                              "Gravitational systems are the ashes of prior electrical systems.". - Hannes Alfven, Nobel Laureate, Plasma physicist.

                              Comment


                              • #30
                                Re: Flex Your PCD Mettle:

                                If it includes minimum phase, then relative offsets are not included, but could be derived by adjusting the individual offsets until the summed response matches the measured combined response. From what I can see, the tweeter is behind the woofer about 2.5" in order to get the result you measured for the raw combined response.
                                Yes, and I got the same result, ~60 mm, which is consistent with the actual physical alignment:

                                Comment

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