Phase Plug design for MW65xx

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Comments

  • xschop
    xschop Posts: 2,022
    3/8-16 x 2" socket head set screws are the ticket....

    w3zpfk8lsbhz.jpg
  • pitdogg2
    pitdogg2 Posts: 18,530
    I wondered where you were going with this ....
  • Gardenstater
    Gardenstater Posts: 1,881
    I think it's really interesting what you are doing here. Do you need to use a high magnetic permeability screw like soft iron or mild steel so as not to have the function of the magnet motor be disturbed in any way, or is the effect of using a regular steel machine screw negligible? How did you end up getting the magnet separated from the pole pieces without damage?
    George / NJ

    Polk 7B main speakers, all 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
  • pitdogg2
    pitdogg2 Posts: 18,530
    stainless or brass would more likely be the ticket if non magnetic comes into play.
  • xschop
    xschop Posts: 2,022
    I have some nylon ones, but the black-oxide is more aesthetic than puke-yellow hehe.

    On a serious note, this exercise convinces me that the pole-piece and magnet must also be concentric or there will be an offset of magnetic force as witnessed by the teetering pull of the steel shim. It goes away when they are true-centered.
    I've seen many of these Polk MWs where their magnets were offset, although functioning.
  • xschop
    xschop Posts: 2,022
    edited May 2020
    I've removed and installed many tapered bearings in Porsche hubs this way.... I had to remove two layers of paper from the duct-tape inner roll. No magnets were harmed lol...

    42npxjfhj7x4.jpg
    45tfr52tish8.jpg

  • Gardenstater
    Gardenstater Posts: 1,881
    edited May 2020
    Ahh so light taps with a hammer on the inner pole piece by way of a soft metal drift and the duct tape *receiver* is soft so as to not damage the magnet. Did you also use heat first to weaken the adhesive?

    How did you get the magnet plus inner pole piece separated from the pole piece that goes between the magnet and the basket?
    George / NJ

    Polk 7B main speakers, all 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
  • xschop
    xschop Posts: 2,022
    I didn't have to use heat. The factory magnet to basket plate adhesive was so oxidized that it gave with a nice controlled hit. When apart and dipped in acetone, it sloughs right off at only a couple microns thick. It's a miracle that the second one never clicked and froze the voice coil in transit or by doing simple mods to them.
  • Gardenstater
    Gardenstater Posts: 1,881
    Great thread! I'm contemplating my next move on the never ending 7B modifications. I have done Dynamat, BlackHole5, XO Sonicaps and Mills/Vishay resistors, all internal wiring and fuse block wiring Cardas Litz and Neotech solid, Cardas Binding Posts.

    Still haven't done Larry's Rings or Hurricane Nuts.

    Should I do phase plugs next? :)
    George / NJ

    Polk 7B main speakers, all 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
  • xschop
    xschop Posts: 2,022
    Unless you disassemble magnet and drill/tap pole piece, your challenge would be to center plug via circular shim and use a double-sided 3M tape.
    Yes, you should IMO.
  • xschop
    xschop Posts: 2,022
    edited January 25
    Next weekend I'll be starting a batch of the MW backer-rings. I have the aluminum dowel on order for more phase plugs so that'll be a couple weekends before I can get to those and I'll get a set out to you if you'd like. My 8TLs will get them surely.
  • Gardenstater
    Gardenstater Posts: 1,881
    Rob that's awesome! PM sent.
    George / NJ

    Polk 7B main speakers, all 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
  • xschop
    xschop Posts: 2,022
    Peeped in to plagiarize my own work hehe.
    Working on a batch of the self-adhesive plugs.
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