Polk Monitor 4, 5, 7 MW6502 magnet shift video...

Mystery
Mystery Posts: 2,543
edited January 25 in Vintage Speakers
This is one of the Polkaudio woofers that has magnet shift.
It's from Monitor 4.5 I think. Date stamp is April 06 1987
I had it in the basement and was working like 8 years ago.
Now it's stiff and frozen.
I can rotate the magnet with hand.
Looks like the magnet and the bottom plate are stuck together while the top plate is shifted.
Either way, it's done for.
What is weird is there is no visible difference around the magnet to see what direction it shifted to.
I know it's in mm but still. I'll see if whacking it with a mallet works. :sweat_smile:


Sonus Faber Concerto Grand Piano, Klipsch, B&W DM602.5, Epicure 20+, T/E 280, 100V, Polk.
Subwoofers: Monitor Audio, B&W ASW300, Triad ProSub Bronze.

Comments

  • xschop
    xschop Posts: 2,050
    As long as they ohm out they are repairable.
  • Mystery
    Mystery Posts: 2,543
    xschop wrote: »
    As long as they ohm out they are repairable.

    Maybe too much work.
    BTW, I was applying epoxy to another good driver and I saw it was pretty dirty.
    I started cleaning it with Windex and a cloth.
    Set it down to dry and checked few hours later to find it just locked up.
    So the magnet shifted when I was cleaning the cone.
    What the H E L L...
    I should have waited till the epoxy worked in. :(
    Be careful when cleaning the cone without epoxying the magnets first.

    Sonus Faber Concerto Grand Piano, Klipsch, B&W DM602.5, Epicure 20+, T/E 280, 100V, Polk.
    Subwoofers: Monitor Audio, B&W ASW300, Triad ProSub Bronze.
  • Gardenstater
    Gardenstater Posts: 2,026
    My god man, are you sure you didn't use that Ajax the White Tornado cleaner?

    https://www.youtube.com/watch/6K722Mer0ow

    But seriously, you would be a prime candidate at this point to purchase one of xschop's driver repair fixtures if he has any still available.
    George / NJ

    Polk 7B main speakers, std. mods+ (1979, orig owner)
    Martin Logan Dynamo sub w/6ft 14awg Power Cord
    Crown D150 amp
    Logitech Squeezebox Touch Streamer w/EDO applet
    iFi nano iDSD DAC
    iPurifier3
    iDefender w/ iPower PS
    Custom Steve Wilson 1m UPOCC Interconnect
    iFi Mercury 0.5m OFHC continuous cast copper USB cable
    Custom Ribbon Speaker Cables, 5ft long, 4N Copper, 14awg, ultra low inductance
    Custom Vibration Isolation Speaker Stands and Sub Platform
  • Mystery
    Mystery Posts: 2,543
    edited January 26
    My god man, are you sure you didn't use that Ajax the White Tornado cleaner?

    https://www.youtube.com/watch/6K722Mer0ow

    But seriously, you would be a prime candidate at this point to purchase one of xschop's driver repair fixtures if he has any still available.

    It never happened to me before.
    I wasn't cleaning it roughly either.
    Just dabbed cloth with Windex and wiped the cone. Of course have to press the cone slightly but can't imagine that was enough for magnet shift. 😡

    Sonus Faber Concerto Grand Piano, Klipsch, B&W DM602.5, Epicure 20+, T/E 280, 100V, Polk.
    Subwoofers: Monitor Audio, B&W ASW300, Triad ProSub Bronze.
  • Gardenstater
    Gardenstater Posts: 2,026
    I think in your case the adhesive had already lost its bond and the only thing holding things in relative positions was the force of magnetic attraction. Who knows if these drivers were stored in a temperature controlled environment all their lives.
    George / NJ

    Polk 7B main speakers, std. mods+ (1979, orig owner)
    Martin Logan Dynamo sub w/6ft 14awg Power Cord
    Crown D150 amp
    Logitech Squeezebox Touch Streamer w/EDO applet
    iFi nano iDSD DAC
    iPurifier3
    iDefender w/ iPower PS
    Custom Steve Wilson 1m UPOCC Interconnect
    iFi Mercury 0.5m OFHC continuous cast copper USB cable
    Custom Ribbon Speaker Cables, 5ft long, 4N Copper, 14awg, ultra low inductance
    Custom Vibration Isolation Speaker Stands and Sub Platform
  • Mystery
    Mystery Posts: 2,543
    edited January 26
    I think in your case the adhesive had already lost its bond and the only thing holding things in relative positions was the force of magnetic attraction. Who knows if these drivers were stored in a temperature controlled environment all their lives.

    Could be.
    Now my peerless monitor 4 are incomplete.
    That MW6502 was for them. :(
    No wonder people butcher Polk speakers to part drivers out as these fail so often and so easily.

    Sonus Faber Concerto Grand Piano, Klipsch, B&W DM602.5, Epicure 20+, T/E 280, 100V, Polk.
    Subwoofers: Monitor Audio, B&W ASW300, Triad ProSub Bronze.