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  • Pwr Ryd

    So you want to use the $20 10" woofer in a 1.5cu ft. enclosure.
    http://www.parts-express.com/pe/show...number=290-912

  • #2
    Re: Ovq Oxc

    Originally posted by moron#99 View Post
    So you want to use the $20 10" woofer in a 1.5cu ft. enclosure.
    http://www.parts-express.com/pe/show...number=290-912
    50's with a +3dB boom at 80 cps? Not me. You?

    Comment


    • #3
      Re: Ovq Oxc

      Originally posted by Chris Roemer View Post
      50's with a +3dB boom at 80 cps? Not me. You?
      no boom. we'll take care of that bump in due process. I not planning vented so the bump might be more like 5 or 6 db at 60hz. no worries though. It will go away.

      Comment


      • #4
        Re: Pwr Pyd

        I don't know how you guys are getting such large humps. Here's what I model (using the factory supplied specs) in a 1.5 Ft^3 closed box with an aperiodic vent:



        The bump is only 0.42 dB at 102 Hz. Qtc is 0.824

        I do have 2 of these drivers at home. I broke them in a couple of weeks ago. I will measure their T/S parameters tonight and post them here.
        Craig

        Comment


        • #5
          Re: Pwr Pyd

          Originally posted by PWR RYD View Post
          I don't know how you guys are getting such large humps. Here's what I model (using the factory supplied specs) in a 1.5 Ft^3 closed box with an aperiodic vent:

          The bump is only 0.42 dB at 102 Hz. Qtc is 0.824 I do have 2 of these drivers at home. I broke them in a couple of weeks ago. I will measure their T/S parameters tonight and post them here.
          sealed box . I always use sealed box. With sealed box you can redefine the driver however it suits you.
          my bad on the hump. i have to get a real calculator.

          alpha = Vas/Vab (Vb corrected for fill ~ 1.15 * 1.5) = 2.81
          Qtc = Qts * SQRT (1+alpha) = 0.62 * SQRT (1.95) = 1.21
          20 log (1.21) = +1.65dB (at 64Hz)

          before this point in a design I would verify feasibility by checking against Qm and Qe. I'll probably do that at lunch or after dinner. At this point in a real prototype I would stop and measure actual Qtc and Fb in the box.

          Comment


          • #6
            Re: Pwr Pyd

            Originally posted by PWR RYD View Post
            I don't know how you guys are getting such large humps. Here's what I model (using the factory supplied specs) in a 1.5 Ft^3 closed box with an aperiodic vent:



            The bump is only 0.42 dB at 102 Hz. Qtc is 0.824

            I do have 2 of these drivers at home. I broke them in a couple of weeks ago. I will measure their T/S parameters tonight and post them here.
            Got to LOVE those aperiodic vents ! :D

            Comment


            • #7
              Re: Pwr Pyd

              The one I measured had a "Q" of 0.75... Fs and Vas were close to spec, though. Within 5% or so IIRC.
              Don't listen to me - I have not sold any $150,000 speakers.

              Comment


              • #8
                Re: Pwr Pyd

                Originally posted by johnnyrichards View Post
                The one I measured had a "Q" of 0.75... Fs and Vas were close to spec, though. Within 5% or so IIRC.
                if there was a case of 50 ... what would you use for T/S? Not trying to say anything. It's just an exercise. But if you have experience then that's got to be better than the marketing department numbers.

                Comment


                • #9
                  Re: Pwr Pyd



                  Obviously Johnny's numbers are the only safe numbers. Logic allows two possibilities:

                  1. Johnny's sample is representative of ALL samples
                  His driver deviates from the manufacturer's spec. The manufacturer's numbers are optimistic at best, or do not represent changes that occured in manufacturing. Clearly manufacturer's specs can't be trusted.

                  2. Johnny's sample is NOT representative of ALL samples
                  His driver is a QC failure and should not be taken as a useful number.

                  If we allow this second option to be true, then we'd have to allow that this driver was not the only suspect driver. It's possible, but highly improbable, that the one faulty driver fell into the hands of a guy capable of measuring it's performance. If there's one faulty driver, then we must logically allow that there are likely to be more faulty drivers, and that means the manufacturer's specs can't be trusted!

                  (I bet you read that in Vizzini's voice)
                  nothing can stop me now

                  Comment


                  • #10
                    Re: Pwr Pyd

                    yeah, plus Johnny has a little hands-on and a lot of prior experience. he may say the driver was cheaply built with sloppy details and to expect a lot of variation from driver to driver. or maybe the driver was precisely built from cheap materials and his test is probably a good average.

                    Comment


                    • #11
                      Re: Pwr Pyd

                      I have two drivers that I will measure when I get home tonight. If they measure close to each other that should rule out a possible manufacturing defect. Both of my drivers are fully broken in (driven to xmax for 8 hours).
                      Craig

                      Comment


                      • #12
                        Re: Pwr Pyd

                        Originally posted by PWR RYD View Post
                        I have two drivers that I will measure when I get home tonight. If they measure close to each other that should rule out a possible manufacturing defect. Both of my drivers are fully broken in (driven to xmax for 8 hours).
                        lol. obviously not an Enya fan.

                        OK. I assigned Qtc=1.21 and then solved for alpha using Qm and Qe. I came up to 2.95 which indicates that the published specs are fairly consistent with each other. Or my math is bad. one or the other. If my math is good then the published Vas might be a little smaller than actual.

                        The next step is to calculate or measure T/S of the woofer mounted in a 1.5u ft. sealed (airtight) box.

                        Comment


                        • #13
                          Re: Pwr Pyd

                          What's an Enya?
                          Craig

                          Comment


                          • #14
                            Re: Pwr Pyd

                            Originally posted by PWR RYD View Post
                            What's an Enya?
                            Craig- Think about the music for Crystal Light commercials, and you'll know what an Enya is.... :rolleyes:
                            Wolf
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                            • #15
                              Re: Pwr Pyd

                              is there a real world F/R on this thing? I keep thinking that if you put this woofer in a three way speaker down at CrazyBob's Audio Emporium then you'll never sell any. Crazy Bob will talk the customers into buying the 12" 3way for a few dollars more. Your real sales pitch is going to be small cabinet, extended bass, student budget, great for dorms. That screams two-way to me.

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