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Markaudio Alpair 6P Measurements

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  • Markaudio Alpair 6P Measurements

    Well I picked up a Markaudio Alpair 6P Gen 2 (6.2 or whatever :D) for testing, thinking I'll use that in a 3-way with shallow slope crossovers. Right now I'm envisioning an OX20 for the top end, and then some nice pair of 8" or a 10" for the bottom. Here is the first measurement. I did no break in, besides listen to some music. Its on a test baffle (flush and rears routed out for breathing room) 12" wide and 4.25" from the top, like so:

    Click image for larger version

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    What you can't see behind that is a poorly (but effectively) mated .25 cubic foot PE box providing what could pass as a rear enclosure. I took these measurements with my ECM8000 at 6.5" from the cone (somewhat nearfield) on 0, 30, and 60 degrees. The voltage was calibrated by meter to 2.8V. The off-axis plots are scaled at -5 and -10 db for visibility.

    Click image for larger version

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    Well alright, so there is an impressive dip from 1000 to 2000 hz with a deep base, -5 db at its worst. Also, some kind of 1200hz 2 order harmonic distortion hiccup. Both of these issues begin to fade when you move off-axis however. So I wonder what the cause is, perhaps cone geometry?

    Its interesting that I could not detect the dip or 2nd order peak in my listening, but I didn't do anything extended. I just crossed it over at 150 hz to my subwoofer and gave it a quick listen on acoustic stuff I know well. It sounded nice and balanced, with too much top end sizzle (I could hear the peak above 10k).

    More tests to come.
    Last edited by JasonP; 10-31-2013, 04:22 PM. Reason: Corrected frequency error 1200 hz
    Audio: Media PC -> Sabre ESS 9023 DAC -> Behringer EP2500 -> (insert speakers of the moment)
    Sites: Jupiter Audioworks - Flicker Stream - Proud Member of Midwest Audio Club

  • #2
    Re: Markaudio Alpair 6P Measurements

    How does it sound 15 degrees off axis (vertical)?

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    • #3
      Re: Markaudio Alpair 6P Measurements

      Off-axis 15 degrees (or so) the top-end boost droops and it sounds nice.

      Here is an in-room at 1 meter with N6 smoothing and the raw measurement in gray underneath. Its not bad at all, nicely done Markaudio.

      Click image for larger version

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      Audio: Media PC -> Sabre ESS 9023 DAC -> Behringer EP2500 -> (insert speakers of the moment)
      Sites: Jupiter Audioworks - Flicker Stream - Proud Member of Midwest Audio Club

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      • #4
        Re: Markaudio Alpair 6P Measurements

        I am a big fan of mark audio. I am using the alpair10 in my Intrepids crossed 1st order HP at 300 and 3k LP 2ND order, electrical on both. The enclosure is about .375 sealed and heavily stuffed.
        At Iowa Mike Jennens brought in a pair of paper cone 70s that really sounded nice, no filtering vented box.
        https://www.facebook.com/Mosaic-Audi...7373763888294/

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        • #5
          Re: Markaudio Alpair 6P Measurements

          Originally posted by isaeagle4031 View Post
          ... I am using the alpair10 in my Intrepids ...
          Indeed, this is what made me start looking at them I just figured I'd try the smaller, most cost-effective model.
          Audio: Media PC -> Sabre ESS 9023 DAC -> Behringer EP2500 -> (insert speakers of the moment)
          Sites: Jupiter Audioworks - Flicker Stream - Proud Member of Midwest Audio Club

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          • #6
            Re: Markaudio Alpair 6P Measurements

            very cool!
            https://www.facebook.com/Mosaic-Audi...7373763888294/

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            • #7
              Re: Markaudio Alpair 6P Measurements

              I've measured larger Alpair driver and it showed similar issues between 1khz and 2khz. Is you cabinet stuffed? Could it be 9" related standing wave?
              http://www.diy-ny.com/

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              • #8
                Re: Markaudio Alpair 6P Measurements

                Originally posted by JasonP View Post
                Well alright, so there is an impressive dip from 1000 to 2000 hz with a deep base, -5 db at its worst. Also, some kind of 2khz 2 order harmonic distortion hiccup. Both of these issues begin to fade when you move off-axis however. So I wonder what the cause is, perhaps cone geometry?
                A carefully designed narrow baffle could potentially fill a good part of that dip with a diffraction bump. At least some part of it.

                Eg : Click image for larger version

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                Almost 2 db of correction in the right spot.

                Chuck

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                • #9
                  Re: Markaudio Alpair 6P Measurements

                  Originally posted by NyxOne View Post
                  A carefully designed narrow baffle could potentially fill a good part of that dip with a diffraction bump. At least some part of it.
                  Right, and that is also why if you compare the 1M measurement to the closer one, you can see the lower part of it has been filled in. That would be an easy solution to the response dip, its worth investigating.
                  Audio: Media PC -> Sabre ESS 9023 DAC -> Behringer EP2500 -> (insert speakers of the moment)
                  Sites: Jupiter Audioworks - Flicker Stream - Proud Member of Midwest Audio Club

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                  • #10
                    Re: Markaudio Alpair 6P Measurements

                    Originally posted by r-carpenter View Post
                    . Is you cabinet stuffed? Could it be 9" related standing wave?
                    Its stuffed full of Acousta-Stuf, maybe too full. Well I can play with that during retest, but I doubt its a rear wave issue. I'll see if there is a bump in impedance at that point too, I bet there is. I'm starting to wonder if it something to do with an internal reflection, the whole motor is rather sealed.
                    Last edited by JasonP; 10-31-2013, 05:46 PM.
                    Audio: Media PC -> Sabre ESS 9023 DAC -> Behringer EP2500 -> (insert speakers of the moment)
                    Sites: Jupiter Audioworks - Flicker Stream - Proud Member of Midwest Audio Club

                    Comment


                    • #11
                      Re: Markaudio Alpair 6P Measurements

                      In my continuing examination, I took a rear measurement from very near the driver, like so:

                      Click image for larger version

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                      Ignore the socks please, I live alone :P

                      That looks like so:

                      Click image for larger version

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                      I'm going to take a stab at the distortion issue and droop in response between 1 to 2 khz: Its likely a cone issue, material + geometry. Note that the 2nd order (all I'm showing, higher orders are much lower) peak is much lower here.

                      I'm sort of interested in seeing what would happen if I opened the little cap on the cone, or played with other cone altering options, but I'm not sure I want to trash a driver that costs more than 50 bucks. Call me cheap. Also, those two issues are the only ones present in an otherwise perfect driver. I mean the distortion would be impressively clean, and the response virtually ruler fact excluding the very top octave.
                      Audio: Media PC -> Sabre ESS 9023 DAC -> Behringer EP2500 -> (insert speakers of the moment)
                      Sites: Jupiter Audioworks - Flicker Stream - Proud Member of Midwest Audio Club

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                      • #12
                        Re: Markaudio Alpair 6P Measurements

                        A resonance should remain in the off-axis. The dip looks to be diffraction. Do a sim in The Edge or better yet, the BDS or Jeff's spreadsheet.

                        dlr
                        WinPCD - Windows .NET Passive Crossover Designer

                        Dave's Speaker Pages

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                        • #13
                          Re: Markaudio Alpair 6P Measurements

                          Originally posted by dlr View Post
                          A resonance should remain in the off-axis. The dip looks to be diffraction. Do a sim in The Edge or better yet, the BDS or Jeff's spreadsheet.

                          dlr
                          Ok, but I've never seen diffraction rear its head in a 2 inch measurement. The dip is real and from the driver best I can tell.
                          Audio: Media PC -> Sabre ESS 9023 DAC -> Behringer EP2500 -> (insert speakers of the moment)
                          Sites: Jupiter Audioworks - Flicker Stream - Proud Member of Midwest Audio Club

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