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  • Experienced FR Graph Analyst Wanted - Minimal Hours, Low Low Pay

    I would welcome observations on this woofer's FR graph ...

    Woofer.png

  • #2
    Is that supposed to be manufacturer data? If not, then there's nothing really to comment on without the measurement conditions like mic distance, baffle size, driver size, location on baffle, distance to walls, floor, ceiling, etc. Without any data, all I can say is you have a reflection occuring at 80Hz. Other than that, it sure looks wiggly...
    "I just use off the shelf textbook filters designed for a resistor of 8 ohms with
    exactly a Fc 3K for both drivers, anybody can do it." -Xmax

    Comment


    • #3
      It is an mfg graph. I was looking for a second opinion to confirm the probable reflection at 80 Hz

      Also, looking at the ~7 dB dip 1.5K Hz. Break up?

      Comment


      • #4
        That's one weird curve. Down below 200 Hz or so, a driver's response curve can basically be predicted by t/s parameters, unless there's something grossly wrong with the driver.
        Brian Steele
        www.diysubwoofers.org

        Comment


        • #5
          Originally posted by Millstonemike View Post
          It is an mfg graph. I was looking for a second opinion to confirm the probable reflection at 80 Hz

          Also, looking at the ~7 dB dip 1.5K Hz. Break up?
          What manufacturer, may I ask? And what size is the driver? 1.5kHz is likely breakup, easier to be sure knowing the size of the driver and the cone material. 80Hz reflection is too low in freq to be caused by the driver iteself, this is more like a back wall behind a measurement baffle. You should not expect this from an infinite baffle measurement.
          "I just use off the shelf textbook filters designed for a resistor of 8 ohms with
          exactly a Fc 3K for both drivers, anybody can do it." -Xmax

          Comment


          • #6
            Originally posted by dcibel View Post

            What manufacturer, may I ask? And what size is the driver? 1.5kHz is likely breakup, easier to be sure knowing the size of the driver and the cone material. 80Hz reflection is too low in freq to be caused by the driver iteself, this is more like a back wall behind a measurement baffle. You should not expect this from an infinite baffle measurement.
            And you triggered an idea when you asked if it's a mfg graph. Most all the mfg's 10" and 12" woofers have the same dip at circa 80 Hz. And most of those graphs are kind of wonky.

            It is a cheap MCM 12" 8 Ohm woofer with high Qts; poly cone and rubber surround. I'm using it to replace the missing woofers in a pair of Large Advents. I know, I know. Not the right driver for the application.

            But according to WinISD, it models the best of some 40 to 50 woofers I've analysed with an F3 circa the original woofers at 46 Hz. In WinPCD I have the breakup down ~25 dB at 2K. The original tweeters are intact. But they're falling off below 2K so there's a 3 dB dip between 1300 and 1800 or so. But the speakers were a find and they're kind of common - utility cab version. So I wasn't going to spend hundreds buying and re-foaming original woofers. I'll use them as test beds for the digital amps I'm evaluating.

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            • #7
              Well the good news is that you can disregard the performance below 200Hz and use your cabinet model instead. As for the response above 1kHz, it is not surprising, a 12" driver will be into breakup modes starting around 800-900Hz.
              "I just use off the shelf textbook filters designed for a resistor of 8 ohms with
              exactly a Fc 3K for both drivers, anybody can do it." -Xmax

              Comment


              • #8
                The natural roll off above 3000 hz and the lack of sharp peaks at the high end should make for a relatively easy crossover.

                Comment


                • #9
                  Is that the MCM "Direct Replacement Series"? If so, you might like it quite a bit, they are pretty similar to the GRS drivers, very similar in fact, and I used the 12" in my monkey coffin build a few years ago.
                  Don't listen to me - I have not sold any $150,000 speakers.

                  Comment


                  • #10
                    Originally posted by johnnyrichards View Post
                    Is that the MCM "Direct Replacement Series"? If so, you might like it quite a bit, they are pretty similar to the GRS drivers, very similar in fact, and I used the 12" in my monkey coffin build a few years ago.
                    Under Newark Electronics, the new distributor for the MCM drivers they're called the 'Audio Select Series". I don't recall seeing "Direct Replacement".

                    But, thanks. I'm was having second thoughts - looks like there's lots of smoothing in the measurements. I couldn't consider the GRS woofers as they have no graph. I don't have measurement equipment nor the experience or hearing to do an XO without WinPCD.

                    Comment


                    • #11
                      No driver is ever going to chart like that in a standard wall mounted baffle measured anechoic. As mentioned already ignore that chart below 200Hz, model it to see what it really will do in your enclosure.
                      www.billfitzmaurice.com
                      www.billfitzmaurice.info/forum

                      Comment


                      • #12
                        Originally posted by billfitzmaurice View Post
                        No driver is ever going to chart like that in a standard wall mounted baffle measured anechoic. As mentioned already ignore that chart below 200Hz, model it to see what it really will do in your enclosure.
                        I've been modeling; 40+ woofers.

                        The WinISD model looks pretty good with an F3 of 46 Hz - just about the same as the original. The WinPCD model, not as nice. The tweeter graph is a measurement I found online from the original speaker including the XO in the response. I had to "guess" on SPL from many comments online. So the tweeter HP remains intact - maybe a pad needed if it's hot.. I'm using the original inductor 1.6 mH 1st order LP on the woofer but added a tank and made it 2nd order with a cap/resistor as shown in the model. $48 for the woofers including shipping and another $$5 for XO parts I didn't have on hand. If it's not a total bust, another $20 recreating the grill.

                        Comment


                        • #13
                          OK, some digging indicates that is the so-called "direct replacement series" 12" woofer sold by a competitor. You will like how it sounds, but you will probably have to pad the tweeter a bit. It is pretty much identical to the 12" I used in this:

                          http://techtalk.parts-express.com/fo...rs-based-3-way
                          Don't listen to me - I have not sold any $150,000 speakers.

                          Comment


                          • #14
                            Originally posted by johnnyrichards View Post
                            OK, some digging indicates that is the so-called "direct replacement series" 12" woofer sold by a competitor. You will like how it sounds, but you will probably have to pad the tweeter a bit. It is pretty much identical to the 12" I used in this:

                            http://techtalk.parts-express.com/fo...rs-based-3-way
                            Looks identical. T/S spec.'s are different. In the Advent cab,WinISD shows a lower F3 but a 3 dB hump at 60 Hz. And the GRS exceeds xmax at 1/3 it's rated 100 W where the MCM can take 2/3 it's rated 100 W). I wonder if the GRS F3 at 37 Hz with the hump would have been a better sound than the MCM's nearly flat response, F3 at 46 Hz. No matter, without a FR graph, I'm handicapped.

                            Do you why they're different? Altered to MCM's spec.'s?

                            Yep, have an assortment of padding resistors on hand ...

                            Comment


                            • #15
                              They are actually closer than advertised, just FYI
                              Don't listen to me - I have not sold any $150,000 speakers.

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