Magnet Shift Repair Solved...for me that is.

124»

Comments

  • txcoastal1txcoastal1 Posts: 11,619
    He’s using them as spacers
    2-channel: Modwright KWI-200 Integrated, Dynaudio C1-II Signatures
    Desktop rig: LSi7, Polk 110sub, Dayens Ampino amp, W4S DAC/pre, Sonos, JRiver
    Gear on standby: Melody 101 tube pre, Unison Research Simply Italy Integrated
    Gone to new homes: (Matt Polk's)Threshold Stasis SA12e monoblocks, Pass XA30.5 amp, Usher MD2 speakers, Dynaudio C4 platinum speakers, Modwright LS100 (voltz), Simaudio 780D DAC

    erat interfectorem cesar et **** dictatorem dicere a
  • GardenstaterGardenstater Posts: 1,659
    edited August 2020
    I'm glad it's clear to you. The picture seems to show a pole piece and a basket with a ring gauge inserted between the two. That sure can't be a voice coil former! So if the ring gauge weren't in there I guess those wires fit in between the basket and the pole piece, and the magnet which is already glued to the pole piece is moved around (with an aluminum vice clamped to it) to fine tune before the epoxy between the magnet and basket has time to set up. But the question is, if one already has a ring gauge that is the proper size, why not just use that instead of all those wire pieces? PS: I guess I can see the advantage of the wires to be used as initial "feeler gauges" and to find the high spots to know which way you have to move the magnet/pole piece vs the basket to get it exactly center so the ring gauge (must be aluminum) fits in.
    Post edited by Gardenstater on
    George / NJ

    Polk 7B main speakers, most mods comp. (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
  • dcmeigsdcmeigs Posts: 707
    edited August 2020
    Shirley here. There is no ring gauge there. I don't have one. Obviously the cone and voice coil have been removed. I measured the gap between the pole piece and the basket and discovered I need a set of shims exactly the size of 18 gauge solid core wire. So... Why not?

    I purchased a replacement driver in perfect shape and used it in my RT5 and so I'm left with either tossing these driver parts or making an attempt at repair. What you see is a COVID madness project, haha.
    Post edited by dcmeigs on
    The world is full of answers, some are right and some are wrong. - Neil Young
  • GardenstaterGardenstater Posts: 1,659
    OK thanks. It looks like there is a ring in there. I see now that the 18 gauge *stripped* wire would have a dia. of about 0.040" and that is apparently what you have there for the annular space for the voice coil to get centered up into and then you will do the final centering of the voice coil when you glue the surround to the basket by using some flexible shims between the ID of the voice coil and the pole piece? That's one way to do it I guess. :)
    George / NJ

    Polk 7B main speakers, most mods comp. (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
  • dcmeigsdcmeigs Posts: 707
    edited August 2020
    You are mostly correct. The 40 thousandth diameter bare wire is the shim, period. Some of the wires are in a bind, pinched by the pole piece which is drawn off center by magnetic forces. Once the epoxy is in place I mounted the assembly in the vice oriented to force the pole piece to the center as the vice is tightened until all the wires are equally loose while the epoxy sets. That part appears to be successful. Tomorrow I'll replace the cone and voice coil. Downinmexico's approach is by far the better, but I dont have the lathe or the skill set to pull that off. Hat's off to him.
    The world is full of answers, some are right and some are wrong. - Neil Young
  • BlueBirdMusicBlueBirdMusic Registered User Posts: 1,384
    Alright I can't take it any longer.......what are these wire segments I'm looking at? Surely those can't be voice coil to pole piece gap spacers (sorry for calling you Shirley). :D

    @Gardenstater, I'm glad you asked the question. I read it yesterday and I was confused to no end. I did not know what question to ask. I thought a picture or two had been omitted.
    If the telephone doesn't ring ......... it's me
    Harry / Marietta Georgia
  • GardenstaterGardenstater Posts: 1,659
    dcmeigs wrote: »
    You are mostly correct. The 40 thousandth diameter bare wire is the shim, period. Some of the wires are in a bind, pinched by the pole piece which is drawn off center by magnetic forces. Once the epoxy is in place I mounted the assembly in the vice oriented to force the pole piece to the center as the vice is tightened until all the wires are equally loose while the epoxy sets. That part appears to be successful. Tomorrow I'll replace the cone and voice coil. Downinmexico's approach is by far the better, but I dont have the lathe or the skill set to pull that off. Hat's off to him.

    Could you show a picture of the assembly in your vice? Where do you get an aluminum vice and what size is it and orientation relative to basket?
    George / NJ

    Polk 7B main speakers, most mods comp. (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
  • dcmeigsdcmeigs Posts: 707
    edited August 2020
    It’s a zyliss brand. Popular with cruisers and woodworkers. If you think you want one, you might want an older one. The new ones are said to be not as strong. The aluminum vice is obviously handy around magnets but I can’t see why a steel vice wouldn’t work about as well if you’re careful not to get your fingers pinched.

    srq5pymj719c.jpeg
    The world is full of answers, some are right and some are wrong. - Neil Young
  • GardenstaterGardenstater Posts: 1,659
    Question.....Epoxy is probably quite a bit thicker joint than Blue threadlocker or whatever Polk used, does it effect the magnetic field strength? Also, do you need to clamp it to try to squeeze out the excess or does the magnet do all the clamping necessary? The Swiss made Portable Aluminum Vice is very cool. I found some on eBay for about $100 shipped.
    George / NJ

    Polk 7B main speakers, most mods comp. (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
  • lawdogglawdogg Posts: 388
    Apply the adhesive around the perimeter of the magnet, on the edges where it meets the basket on one side and the pole piece on the other. You will avoid issues of uneven adhesive causing the axis of the voice coil and pole piece to be out of alignment. Epoxy isn't ferrous so it shouldn't have any effect on the magnetic field...
    <3 my 3.1TLs

    I will fix your shifted magnets for free. :)
  • GardenstaterGardenstater Posts: 1,659
    edited August 2020
    I just thought that the intimacy of contact (for want of a better word lol) between the magnet and the frame pole piece and the inner pole piece might be somewhat decreased by a more viscous and thicker adhesive layer, and that might affect the strength of the N and S poles nearest the voice coil. There might be a reason why they used such a thin *adhesive* as threadlocker. I know that epoxy is not ferrous but the pole pieces certainly are and maybe they need physical contact with the magnet.

    PS: I guess what I should've said is what is the best adhesive for this, a relatively thick epoxy, or the thin threadlocker?
    George / NJ

    Polk 7B main speakers, most mods comp. (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
  • dcmeigsdcmeigs Posts: 707
    Epoxy is not very viscous until it starts to go off. If you want you could use slower 30 minute or West Systems that takes hours. The clamping force of the magnet will certainly create a thin film. I second Law Dogs comment about biasing the application to the outside away from the pole piece. No clamps required.
    The world is full of answers, some are right and some are wrong. - Neil Young
Sign In or Register to comment.

Howdy, Stranger!

It looks like you're new here. If you want to get involved, click one of these buttons!