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  • Re: Flex Your PCD Mettle:

    Yes, Russell; that's the acoustic center vertically. The woofer and waveguide are symmetrical below and above there, respectively, by 1/2 the center-to-center distance as mounted in the cab.

    The HF always has an L-pad set at 1:00 included in both the FRD and ZMA.

    FRDs include minimum phase.

    The "extra" FRD with both drivers is to assist in making an initial approximation of the HF Z offset, the vertical plane of the acoustic center differential. Import that as overlay and adjust tweeter z with no filters to match, above ~800 Hz. The HF protection cap used in measuring messes with the phase below there....

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    • Re: Flex Your PCD Mettle:

      Originally posted by Zilch View Post

      FRDs include minimum phase.
      This is something that has puzzled me, the "includes minimum phase" part. Is this just inherent due to the measuring protocol, or is this minimum phase info gotten another way?

      I just figured that since the measurement was taken from the fixed location, with the drivers in their fixed locations relative to the measuring device, this phase information would be included? Seems a little too simple.....

      Russellc

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      • Re: Flex Your PCD Mettle:

        Originally posted by Zilch View Post
        The HF protection cap used in measuring messes with the phase below there....
        This sounds important, could you explain proper use
        and proper size of this protection cap? Is this something like when a electronic cross over is used?

        Russellc

        Comment


        • Re: Flex Your PCD Mettle:

          Originally posted by Zilch View Post
          Yes, Russell; that's the acoustic center vertically. The woofer and waveguide are symmetrical below and above there, respectively, by 1/2 the center-to-center distance as mounted in the cab.
          Thank you for this clarification, I'm just starting here and am scaling the learning curve to generate info to use with PCD. This should aid greatly with my attempts to generate FRD and ZMA files on the 2235H in my 4507 box.

          44 inches it is, between the woofer and waveguide.


          Russellc

          Comment


          • Re: Flex Your PCD Mettle:

            Originally posted by Russellc View Post
            This is something that has puzzled me, the "includes minimum phase" part. Is this just inherent due to the measuring protocol, or is this minimum phase info gotten another way?
            PCD requires minimum phase data in order to calculate summation through the crossover region. It's the acoustic phase of the driver alone, without the flight time from its acoustic center to the mic. This can be derived from the drivers' frequency responses in their .frd files via post processing, but CLIO provides it directly if I click the right button.


            Originally posted by Russellc View Post
            This sounds important, could you explain proper use
            and proper size of this protection cap?
            The high-intensity noise signal used to measure impulse and frequency response is full-spectrum in many test systems, unless they allow you to limit the bandwidth. Thus, you must protect tweeters and compression drivers from the lower frequencies to avoid damaging them due to over-excursion if the output bandwidth is not otherwise limited. To accomplish this, standard practice mandates that a protection capacitor be connected in series with the HF driver under test, usually calculated from the driver impedance to limit beginning an octave below the minimum measurement frequency of interest.

            Compression drivers are pretty rugged in this respect, so I don't bother performing that calculation for different ones, rather, simply use a 47 uF capacitor, which for a nominal 8-Ohm driver gets it somewhat below 500 Hz, as a matter of routine. With conventional cone/dome tweeters, I'm somewhat more precise about the value of the protection cap.

            Similar practice applies as standard to active-crossed multi-amp systems, where a turnon or turnoff thump from an amp or crossover, or failure of either, or a high level of DC offset from an amp, can damage a HF driver. Wear protection.

            [Operator error is also a conspicuous factor here; working with $200+ diaphragms, we smarten up plenty quick. ;) ]


            Originally posted by Russellc View Post
            44 inches it is, between the woofer and waveguide.
            No, 44" is the distance from the mic to the centerpoint in my measurements. The center-to-center distance, more typically 12" or less, varies with the space between the centers of the woofer and waveguide....

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            • EconoWave Altec 414-8B:





              Attached Files
              Last edited by Zilch; 12-01-2010, 07:59 PM.

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              • Re: Flex Your PCD Mettle:

                Im new to these pro sound drivers. I am building a big theatre in my basement and im thinking of building 3 EconoWave SR's for LCR. Will these do the job? what should the LF be crossed at 80hz?

                Comment


                • Re: Flex Your PCD Mettle:

                  Yes, a recommended "budget" HT build, in fact.

                  Parts Express is working on restoring 152i waveguide availability for us (QSC discontinued selling them direct to DIYers), and we are hopeful that may happen soon....

                  Comment


                  • Re: Flex Your PCD Mettle:

                    Originally posted by Zilch View Post
                    Yes, a recommended "budget" HT build, in fact.

                    Parts Express is working on restoring 152i waveguide availability for us (QSC discontinued selling them direct to DIYers), and we are hopeful that may happen soon....
                    When you say budget how is the sound quality on these speakers?

                    Comment


                    • Re: Flex Your PCD Mettle:

                      Originally posted by giverago View Post
                      When you say budget how is the sound quality on these speakers?
                      I say "budget," because you can build a full reference-level LCR front stage including sub(s) for under $1000.

                      I don't do "How's it sound," basically; you'll have to rely on others who have built EconoWaves for that, and there are hundreds who have done so worldwide. Click the "Member Projects" links in the first post of this thread to see some of the builds completed here in Tech Talk, for example. "First" at the top or bottom of any page in this thread will take you there, and Google will lead you to bunches more....

                      Comment


                      • Re: Flex Your PCD Mettle:

                        Originally posted by Zilch View Post
                        Yes, a recommended "budget" HT build, in fact.

                        Parts Express is working on restoring 152i waveguide availability for us (QSC discontinued selling them direct to DIYers), and we are hopeful that may happen soon....
                        Good to hear I e-mailed them a week or so about this.


                        Zilch, what advantages does the HO have over the deluxe? It looks like the HO trades a higher efficiency for a higher FS, not really important if you are looking at an 80hz cross with a sub a theater.
                        I am kinda waffling between the SR and the deluxe though, someone commisioned me to build some speakers for them after hearing my setup and I figured the E-wave is the best way to go. Trying to determine if the deluxe is worth twice the price, figured on deluxe's for the LCR's and a 10E on the rears.
                        My simple speaker project
                        My simple subwoofer project

                        The Inlaws Hometheater

                        Comment


                        • Re: Flex Your PCD Mettle:

                          All said and done, in this application, "HO" designation relates more to the woofer model than to any significant difference in efficiency between the two systems; there's a more in-depth analysis of this by others posted in those sections of this thread. Neither do they sound appreciably different.

                          In my view, preference goes to Deluxe for its greater low-frequency excursion capability, largely due to my own desire to play it two-channel with assist. I haven't optimized the tuning to take full advantage of that as yet, and this may ultimately prove to be less of a factor than I imagine it might be.

                          HO was prototyped using another member's woofers, so I don't have any here for direct comparison, but by that member's own response when we did the A/B (albeit briefly), it's a tossup....

                          Comment


                          • Re: Flex Your PCD Mettle:

                            [QUOTE=Zilch;1692186]PCD requires minimum phase data in order to calculate summation through the crossover region. It's the acoustic phase of the driver alone, without the flight time from its acoustic center to the mic. This can be derived from the drivers' frequency responses in their .frd files via post processing, but CLIO provides it directly if I click the right button. . [QUOTE/]

                            I'll be using HolmImpluse, so I wont have the button on CLIO, wish I did. Is this phase information calculated by entering all the driver location information into PCD? Or is there some way to generate FDR files with this "minimum phase information" using this software?

                            Originally posted by Zilch View Post
                            The high-intensity noise signal used to measure impulse and frequency response is full-spectrum in many test systems, unless they allow you to limit the bandwidth. Thus, you must protect tweeters and compression drivers from the lower frequencies to avoid damaging them due to over-excursion if the output bandwidth is not otherwise limited. To accomplish this, standard practice mandates that a protection capacitor be connected in series with the HF driver under test, usually calculated from the driver impedance to limit beginning an octave below the minimum measurement frequency of interest.

                            Compression drivers are pretty rugged in this respect, so I don't bother performing that calculation for different ones, rather, simply use a 47 uF capacitor, which for a nominal 8-Ohm driver gets it somewhat below 500 Hz, as a matter of routine. With conventional cone/dome tweeters, I'm somewhat more precise about the value of the protection cap.

                            Similar practice applies as standard to active-crossed multi-amp systems, where a turnon or turnoff thump from an amp or crossover, or failure of either, or a high level of DC offset from an amp, can damage a HF driver. Wear protection.
                            Thanks, I have a couple of big Solen 47 uF polyprop caps that ought to work here...


                            Originally posted by Zilch View Post
                            No, 44" is the distance from the mic to the centerpoint in my measurements. The center-to-center distance, more typically 12" or less, varies with the space between the centers of the woofer and waveguide....
                            Sorry, didnt put it very clearly, I understood you meant that the mic was 44 inches away from the centerpoint, which is the point that is "center" of the center to center distance between the drivers?

                            Comment


                            • Re: Flex Your PCD Mettle:

                              Originally posted by Russellc View Post
                              I'll be using HolmImpluse, so I wont have the button on CLIO, wish I did. Is this phase information calculated by entering all the driver location information into PCD? Or is there some way to generate FDR files with this "minimum phase information" using this software?
                              Holm does minimum phase; I used it for one of the projects in this thread.


                              Originally posted by Russellc View Post
                              Sorry, didnt put it very clearly, I understood you meant that the mic was 44 inches away from the centerpoint, which is the point that is "center" of the center to center distance between the drivers?
                              Correct.

                              75035/1032=72.7083

                              Comment


                              • Re: Flex Your PCD Mettle:

                                Originally posted by Zilch View Post
                                Holm does minimum phase; I used it for one of the projects in this thread.
                                Here is a post from JeffB about minimum phase and PCD. This is from the "RE Jeff B's spreadsheet: How to import data" thread that was just posted

                                "My interpolator does not extract minimum phase from the frequency response. You need to use the Hilbert-Bode transform in the Response Modeler for that function. If your phase data is all zeros then that is what you will import. The frd import function only brings in what you have in the file."

                                Havent got to that peak in the learning curve yet, can anyone shed a little light on that?

                                Any and all help much appreciated!

                                Russellc

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