Announcement

Collapse
No announcement yet.

What to do about this?

Collapse
X
  • Filter
  • Time
  • Show
Clear All
new posts

  • What to do about this?

    Hello,



    I finally have come around to use my DATS impedance tool on some of my drivers.



    Now, I thought that I had a small fortune in the workshop, consisting of three Dynaudio D28AF tweeters but their impedance curves are like the one attached.



    Are my drivers repairable, perhaps by replacing the magnetic fluid inside of them, or are they ready for the garbage bin?



    Regards//lasse

    Stockholm, Sweden

    Click image for larger version  Name:	Bild Impedans D28AF.JPG Views:	1 Size:	276.1 KB ID:	1401874
    Perry Mason talking to his dentist:

    "Do you swear to take the tooth, the whole tooth and nothing but the tooth, so help you God?"

  • #2
    Do they make "sound"?
    Is your DATS working (do a Z-sweep on your last project)?
    They look like a very small value inductor...

    Comment


    • #3
      The resonant spike comes from mechanical resonance, which these do not appear to have. As Chris said, they measure like small inductors, which means the coil is likely intact but the cone is not moving. If they have (maybe had) ferrofluid, maybe the fluid has dried out and left all the solids, effectively gluing the coil in place. Assuming those are service-able, you could open one up, gently, and have a look-see.

      Comment


      • #4
        Hi,

        The attached DATS-scan of one of my AUDAX domes was taken at the same time so the system seems to work.



        Does anyone know how bad ferrofluid show up in a impedance measurement?


        Click image for larger version

Name:	Bild AUDAX mis dome.JPG
Views:	1
Size:	272.6 KB
ID:	1401898
        Perry Mason talking to his dentist:

        "Do you swear to take the tooth, the whole tooth and nothing but the tooth, so help you God?"

        Comment


        • #5
          Originally posted by 1100xxben View Post
          The resonant spike comes from mechanical resonance, which these do not appear to have. As Chris said, they measure like small inductors, which means the coil is likely intact but the cone is not moving. If they have (maybe had) ferrofluid, maybe the fluid has dried out and left all the solids, effectively gluing the coil in place. Assuming those are service-able, you could open one up, gently, and have a look-see.
          Hi,

          yes a "autopsy" is probably the next logical move….

          Regards//lasse
          Perry Mason talking to his dentist:

          "Do you swear to take the tooth, the whole tooth and nothing but the tooth, so help you God?"

          Comment


          • #6
            Your images are very hard to see. Try changing the Application Look to Light in the DATS View menu.
            www.billfitzmaurice.com
            www.billfitzmaurice.info/forum

            Comment


            • #7
              I'm not a big fan of ferrofluid, but when you remove it, you have a different tweeter. I agree that the coil's likely frozen. Time for careful dissection and cleaning, but you definitely need to measure thoroughly thereafter. The stock response will change, particularly at the extremes of response (1khz, 12khz)

              Comment


              • #8
                Originally posted by badman View Post
                I'm not a big fan of ferrofluid, but when you remove it, you have a different tweeter. I agree that the coil's likely frozen. Time for careful dissection and cleaning, but you definitely need to measure thoroughly thereafter. The stock response will change, particularly at the extremes of response (1khz, 12khz)
                But isn´t it possible to pour in new ferrofluid?
                Perry Mason talking to his dentist:

                "Do you swear to take the tooth, the whole tooth and nothing but the tooth, so help you God?"

                Comment


                • #9
                  Originally posted by lasse View Post

                  But isn´t it possible to pour in new ferrofluid?
                  Yup. Parts Express sells a general purpose replacement. The stuff that's sold for science experiments will not work.

                  Comment


                  • #10
                    Originally posted by lasse View Post

                    But isn´t it possible to pour in new ferrofluid?
                    You have to clean out the old ferrofluid first, then you can add fresh ferrofluid. I have plenty of experience with adding ferrofluid to tweeters.

                    Comment


                    • #11
                      OK,

                      last question from me on this subject:

                      Has anyone replaced the ferrofluid on a Dynaudio tweeter with good results?

                      Regards//lasse
                      Perry Mason talking to his dentist:

                      "Do you swear to take the tooth, the whole tooth and nothing but the tooth, so help you God?"

                      Comment


                      • #12
                        So... your DATS is working fine.

                        DO they make ANY sound? 'cause (as was said) if they can't move, they won't have a resonance.
                        If they HAD FF, it seems to have evaporated leaving the solids to glue everything up !

                        Comment


                        • #13
                          Originally posted by Chris Roemer View Post
                          So... your DATS is working fine.

                          DO they make ANY sound? 'cause (as was said) if they can't move, they won't have a resonance.
                          If they HAD FF, it seems to have evaporated leaving the solids to glue everything up !
                          So, in theory, the same "symptome" (=no resonance peak) could be seen after a over-heat situation with a damaged coil?

                          Regards//lasse
                          Perry Mason talking to his dentist:

                          "Do you swear to take the tooth, the whole tooth and nothing but the tooth, so help you God?"

                          Comment


                          • #14
                            Originally posted by lasse View Post

                            So, in theory, the same "symptome" (=no resonance peak) could be seen after a over-heat situation with a damaged coil?

                            Regards//lasse
                            Most likely, an overheat that actually damaged the coil would result in an open circuit.

                            Comment


                            • #15
                              Is the more probable failure-mode for tweeters to have an open circuit than a overheated and misaligned/stuck voicecoil?
                              Perry Mason talking to his dentist:

                              "Do you swear to take the tooth, the whole tooth and nothing but the tooth, so help you God?"

                              Comment

                              Working...
                              X