Epoxying Magnets - What to Check Beforehand

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_LongWalker_
_LongWalker_ Posts: 1
in Vintage Speakers
I'm pretty darn novice when it comes to audio and audio DIY. I just bought a pair of Monitor 10b's in great condition, and from some reading here, it seems I'd be wise to glue the magnets in place. A 2-part fast epoxy is highly regarded.

Before I attempt this, is there anything I should closely check before applying any type of glue? Make sure the cones are moving freely, and not just with one finger? Anything sound related? And here's probably the silliest question: it's only the mid drivers that I need to be concerned about regarding magnet shift, right?

I'm asking because it seems if I were to glue prematurely, before catching an actual flaw, I'd be in a worse condition. Speakers sound fantastic btw.

Thanks!
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  • F1nut
    F1nut Posts: 49,818
    edited May 2023
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    Use JB Weld, do not use 5 minute epoxy. Apply to the top and bottom around the magnet.

    Yes, only the mid-drivers.

    With fingers spread out evenly gently press the cone in. You should not hear a scraping sound.
    Political Correctness'.........defined

    "A doctrine fostered by a delusional, illogical minority and rabidly promoted by an unscrupulous mainstream media, which holds forth the proposition that it is entirely possible to pick up a t-u-r-d by the clean end."

    President of Club Polk

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  • Gardenstater
    Gardenstater Posts: 4,195
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    I will say that if your speakers have MW6500s, which have a tighter clearance between the VC O.D. and the top plate, I would not use JB Weld because that will be a lot harder to remove should you encounter a rub as they age. I was glad that I didn't on my original 6500s. The Gorilla Max Strength Clear was hard to remove but not impossible. Now I can repair the drivers when I get to it. Future mod platform is what they are now.
    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
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  • F1nut
    F1nut Posts: 49,818
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    A rub as they age...LOL

    That's ridiculous, they are aged already.
    Political Correctness'.........defined

    "A doctrine fostered by a delusional, illogical minority and rabidly promoted by an unscrupulous mainstream media, which holds forth the proposition that it is entirely possible to pick up a t-u-r-d by the clean end."

    President of Club Polk

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  • Gardenstater
    Gardenstater Posts: 4,195
    edited May 2023
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    F1nut wrote: »
    A rub as they age...LOL

    That's ridiculous, they are aged already.

    OK sir, would you prefer as they are played further? My speakers aged quite a bit in their first 5 years of life and were played quite excessively loud :) The more they are played and the louder they are played, the more worn the suspension parts get. What is ridiculous is having to defend the obvious.
    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
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  • F1nut
    F1nut Posts: 49,818
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    I've been playing various Polk speakers excessively loud since 1986. Never a problem.
    Political Correctness'.........defined

    "A doctrine fostered by a delusional, illogical minority and rabidly promoted by an unscrupulous mainstream media, which holds forth the proposition that it is entirely possible to pick up a t-u-r-d by the clean end."

    President of Club Polk

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  • Gardenstater
    Gardenstater Posts: 4,195
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    F1nut wrote: »
    I've been playing various Polk speakers excessively loud since 1986. Never a problem.

    Good for you man. Which ones? The more drivers in the cabinet, the less the individual displacements for a given sPL. Then there is also the quality of amplification and the random element of assembly errors such as a cocked voice coil (etc.) that could easily make it through incoming inspection without being detected.
    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
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  • pitdogg2
    pitdogg2 Posts: 24,603
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    Okay for the sake of the argument.
    Lets say the suspension wears out, are there new suspensions we can buy and replace the old "worn" out suspensions? If so kindly point me in that direction, I'll buy 12 or 20 of them.
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  • bcwsrt
    bcwsrt Posts: 1,608
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    Right. But in any case, with mine recently being firmly J-B Weld-ed in their 30 year-old places, if something bad happens next, I’ll feel like I definitely got my money’s worth and move on to some new speakers.

    Brian

    One-owner Polk Audio RTA 15TL speakers refreshed w/ Sonicap, Vishay/Mills and Cardas components by "pitdogg2," "xschop" billet tweeter plates and BH5 | Stereo REL Acoustics T/5x subwoofers w/ Bassline Blue cables | Rogue Audio Cronus Magnum III integrated tube amp | Technics SL-1210G turntable w/ Ortofon 2M Black LVB 250 MM cart | Sony CDP-508ESD CD player (as a transport) | LampizatOr Baltic 4 tube DAC | Nordost & DH Labs cables/interconnects | APC H15 Power Conditioner | GIK Acoustics room treatments | Degritter RCM
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  • F1nut
    F1nut Posts: 49,818
    edited May 2023
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    Gardenstater wrote: »
    F1nut wrote: »
    I've been playing various Polk speakers excessively loud since 1986. Never a problem.

    Good for you man. Which ones? The more drivers in the cabinet, the less the individual displacements for a given sPL. Then there is also the quality of amplification and the random element of assembly errors such as a cocked voice coil (etc.) that could easily make it through incoming inspection without being detected.

    CRS, CRS+, 2B, RTA15TL, Monitor 7, Monitor 11, 2.3TL and multiple RTiA models.

    Stop over thinking each and every damn thing, you'll live longer.
    Political Correctness'.........defined

    "A doctrine fostered by a delusional, illogical minority and rabidly promoted by an unscrupulous mainstream media, which holds forth the proposition that it is entirely possible to pick up a t-u-r-d by the clean end."

    President of Club Polk

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  • xschop
    xschop Posts: 4,718
    edited May 2023
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    I never met a good engineer that didn't question everything lol.

    Where there's a will, there's a solution. Alot of people have just tossed the drivers before, when the coils start rubbing.

    These spiders are all 4.0" OD x 1.0 ID x 0.5" tall with 6 pleats

    The 6502's are a thicker thread/weave than the others and I have never seen or heard of one's coil rubbing.

    Ticking time bombs...
    6500's
    6503's
    6509's (probably safe as large BP gap)
    6510's GL finding any not worn
    6511's GL finding any not REALLY worn



    Post edited by xschop on
    Don't take experimental gene therapies from known eugenicists.
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  • Gardenstater
    Gardenstater Posts: 4,195
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    pitdogg2 wrote: »
    Okay for the sake of the argument.
    Lets say the suspension wears out, are there new suspensions we can buy and replace the old "worn" out suspensions? If so kindly point me in that direction, I'll buy 12 or 20 of them.

    Maybe you can get the surrounds from Simply Speakers. Are they the same compliance? I don't know. But my point was that if you don't glue with epoxy but choose something that is not so hard to remove but still gives you a tenacious impact resistant bond, you will be more protected in the future and will be able to realign the magnet motor without so much grief.
    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
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  • Gardenstater
    Gardenstater Posts: 4,195
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    F1nut wrote: »
    Gardenstater wrote: »
    F1nut wrote: »
    I've been playing various Polk speakers excessively loud since 1986. Never a problem.

    Good for you man. Which ones? The more drivers in the cabinet, the less the individual displacements for a given sPL. Then there is also the quality of amplification and the random element of assembly errors such as a cocked voice coil (etc.) that could easily make it through incoming inspection without being detected.

    CRS, CRS+, 2B, RTA15TL, Monitor 7, Monitor 11, 2.3TL and multiple RTiA models.

    Stop over thinking each and every damn thing, you'll live longer.

    Every one you mention except the Monitor 7 has 2 or more drivers, which makes them more resistant from over extension at high sPL's. That causes damage over time to the spiders which are basically cotton fabric impregnated with phenolic resin.
    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
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  • F1nut
    F1nut Posts: 49,818
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    Gardenstater wrote: »
    F1nut wrote: »
    Gardenstater wrote: »
    F1nut wrote: »
    I've been playing various Polk speakers excessively loud since 1986. Never a problem.

    Good for you man. Which ones? The more drivers in the cabinet, the less the individual displacements for a given sPL. Then there is also the quality of amplification and the random element of assembly errors such as a cocked voice coil (etc.) that could easily make it through incoming inspection without being detected.

    CRS, CRS+, 2B, RTA15TL, Monitor 7, Monitor 11, 2.3TL and multiple RTiA models.

    Stop over thinking each and every damn thing, you'll live longer.

    Every one you mention except the Monitor 7 has 2 or more drivers, which makes them more resistant from over extension at high sPL's. That causes damage over time to the spiders which are basically cotton fabric impregnated with phenolic resin.

    LMAO...
    Political Correctness'.........defined

    "A doctrine fostered by a delusional, illogical minority and rabidly promoted by an unscrupulous mainstream media, which holds forth the proposition that it is entirely possible to pick up a t-u-r-d by the clean end."

    President of Club Polk

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  • Gardenstater
    Gardenstater Posts: 4,195
    edited May 2023
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    Gardenstater wrote: »
    F1nut wrote: »
    Gardenstater wrote: »
    F1nut wrote: »
    I've been playing various Polk speakers excessively loud since 1986. Never a problem.

    Good for you man. Which ones? The more drivers in the cabinet, the less the individual displacements for a given sPL. Then there is also the quality of amplification and the random element of assembly errors such as a cocked voice coil (etc.) that could easily make it through incoming inspection without being detected.

    CRS, CRS+, 2B, RTA15TL, Monitor 7, Monitor 11, 2.3TL and multiple RTiA models.

    Stop over thinking each and every damn thing, you'll live longer.

    Every one you mention except the Monitor 7 has 2 or more drivers, which makes them more resistant from over extension at high sPL's. That causes damage over time to the spiders which are basically cotton fabric impregnated with phenolic resin.

    In the interest of accuracy it probably only holds true for multiple stereo drivers, that the incidences of over excursions will be less for high sPL.
    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
    · Share on FacebookShare on Twitter
  • bcwsrt
    bcwsrt Posts: 1,608
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    OP has two-driver 10s. Probably sorry he started this thread. Lol

    Brian

    One-owner Polk Audio RTA 15TL speakers refreshed w/ Sonicap, Vishay/Mills and Cardas components by "pitdogg2," "xschop" billet tweeter plates and BH5 | Stereo REL Acoustics T/5x subwoofers w/ Bassline Blue cables | Rogue Audio Cronus Magnum III integrated tube amp | Technics SL-1210G turntable w/ Ortofon 2M Black LVB 250 MM cart | Sony CDP-508ESD CD player (as a transport) | LampizatOr Baltic 4 tube DAC | Nordost & DH Labs cables/interconnects | APC H15 Power Conditioner | GIK Acoustics room treatments | Degritter RCM
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  • odcics2
    odcics2 Posts: 309
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    Hey OP, welcome to this site!!

    :)
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  • xschop
    xschop Posts: 4,718
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    Gardenstater wrote: »
    F1nut wrote: »
    Gardenstater wrote: »
    F1nut wrote: »
    I've been playing various Polk speakers excessively loud since 1986. Never a problem.

    Good for you man. Which ones? The more drivers in the cabinet, the less the individual displacements for a given sPL. Then there is also the quality of amplification and the random element of assembly errors such as a cocked voice coil (etc.) that could easily make it through incoming inspection without being detected.

    CRS, CRS+, 2B, RTA15TL, Monitor 7, Monitor 11, 2.3TL and multiple RTiA models.

    Stop over thinking each and every damn thing, you'll live longer.

    Every one you mention except the Monitor 7 has 2 or more drivers, which makes them more resistant from over extension at high sPL's. That causes damage over time to the spiders which are basically cotton fabric impregnated with phenolic resin.

    Thank you for the "solution".
    Don't take experimental gene therapies from known eugenicists.
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  • xschop
    xschop Posts: 4,718
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    Was not jesting with that comment. Last year when I plugged the original 6516's for the 8TL's, I noticed one of the spiders was more giving/loose than the others. I taped everything off and sprayed a layer of ironing starch on the spider and let dry. It tightened it up very close to the others. I took them out week before last when I installed focus-ringed and phase- plugged 6516's....and it is still holding up, no deterioration. I figured the resin George mentioned could be made into a solution and sprayed as well, to rejuvenate all these old drivers' spiders...
    Don't take experimental gene therapies from known eugenicists.
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  • skrol
    skrol Posts: 3,340
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    The only deterioration I have experienced with the MW65xx (MM65xx for mobile) series spiders is the glue detaching from the basket. That was on two MM6500 and one MW65xx. I just glued them back with a little epoxy and no problem after.

    I have seen shifted magnets cause rubbing and locking. If the VC starts rubbing from loud play, it may be that the VC has deformed due to excessive heating of the coil.
    Stan

    Main 2ch:
    Polk LSi15 (DB840 upgrade), Parasound: P/LD-1100, HCA-1000A; Denon: DVD-2910, DRM-800A; Benchmark DAC1, Monster HTS3600-MKII, Grado SR-225i; Technics SL-J2, Parasound PPH-100.

    HT:
    Marantz SR7010, Polk: RTA11TL (RDO198-1, XO and Damping Upgrades), S4, CS250, PSW110 , Marantz UD5005, Pioneer PL-530, Panasonic TC-P42S60

    Other stuff:
    Denon: DRA-835R, AVR-888, DCD-660, DRM-700A, DRR-780; Polk: S8, Monitor 5A, 5B, TSi100, RM7, PSW10 (DXi104 upgrade); Pioneer: CT-6R; Onkyo CP-1046F; Ortofon OM5E, Marantz: PM5004, CD5004, CDR-615; Parasound C/PT-600, HCA-800ii, Sony CDP-650ESD, Technics SA 5070, B&W DM601
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  • pitdogg2
    pitdogg2 Posts: 24,603
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    If the VC starts rubbing from loud play, it may be that the VC has deformed due to excessive heating of the coil.
    Yuuup.
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  • Gardenstater
    Gardenstater Posts: 4,195
    edited May 2023
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    Both of my originally equipped MW6500s left the factory with cocked voice coils. They are on the alignment fixtures I built and are being coaxed back into alignment by combination of time and blow dryer heat cycles. Neither of them scrape when manually pushed anymore but the VC being cocked is only improved slightly (that's how bad they were built). One of them developed a crack in the spider during it's service life but it was not at the attachment point to the cone and VC. It was near it. Only detectable visibly when I over extended the cone forward. I'm sure the VC being cocked didn't help but neither did my playing them super loud when I was in college with a 55WPC receiver. The VCs never overheated though and are perfectly round as far as I can tell. You can see where they were rubbing on the front plates however by scuff marks in whatever the wire is coated with. They still ohm out correctly at 6.5 ohms.

    m0myie5zwkwa.jpg

    Scuffing from cocked VC's:

    eoafbs8lxwuk.jpg

    This picture gives some idea of how gauz-y the spiders really are (black basket backup driver):

    vskyoqlhpgl9.jpg



    Post edited by Gardenstater on
    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
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  • xschop
    xschop Posts: 4,718
    edited May 2023
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    Clearance the Basplate ID and install some focus rings already.🙂
    Don't take experimental gene therapies from known eugenicists.
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  • Gardenstater
    Gardenstater Posts: 4,195
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    xschop wrote: »
    Clearance the Basplate ID and install some focus rings already.🙂

    I'm actually leaning towards making the front plates alignable/adjustable and leaving the gap what it is, so that the Bxl remains in spec and sensitivity doesn't get reduced.
    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
    · Share on FacebookShare on Twitter
  • xschop
    xschop Posts: 4,718
    edited May 2023
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    B)

    Do your 6500's have a slight air-gap between base plate and frame where the rivets attach?

    I've been finding a few that have this QC issue also, which translates more vibration into the pole-pieces. Remedied one with HDPU and will compare the other with 2-part epoxy in the gap.
    Don't take experimental gene therapies from known eugenicists.
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  • Gardenstater
    Gardenstater Posts: 4,195
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    xschop wrote: »
    B)

    Do your 6500's have a slight air-gap between base plate and frame where the rivets attach?

    I've been finding a few that have this QC issue also, which translates more vibration into the pole-pieces. Remedied one with HDPU and will compare the other with 2-part epoxy in the gap.

    Can't see any light, but the depth to which you can insert a 0.005" feeler gage varies between the two drivers and varies around the circumference of the front plate. This could be part of the problem with the cocked voice coils.

    Mine seem to have come into alignment after almost 14 mos. on the fixtures I made lol.

    But in order to get a 1/8" extension of voice coil you have to make the spiders decidedly concave dish shaped because they were manufactured at only 1/16". That's the next issue to be fixed.
    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
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  • StantonZ
    StantonZ Posts: 440
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    Another data point that might be useful (and supports F1's comments).
    I've played the **** out of my 10B's for over 25 years...and I just epoxy'd them (JB Weld) a couple of years ago before a big move. Once you confirm they are 'good', just do it and don't look back; this is one of those things where an ounce of prevention is worth way more than a pound of cure. The only negative is it's messy/smelly...so make sure you have plenty of ventilation (and wipes).
    Yamaha RX-A2050 AVR (5.0.2); LG OLED77C2 4K TV
    (4) Polk Monitor 10B's w/SoniCaps, Mills, and RDO-194 tweets (R/L F/R)
    (2) Polk RC80i (Top Middle)
    Polk CS300 center channel
    Analog: B&O TX2 Turntable, Nakamichi Cassette Deck 1
    Digital: Pioneer CLD-99 Elite LD, Panasonic DMP-UB900 UHD Blu-Ray
    Bedroom: Arylic Up2Stream AMPv3 driving Polk Monitor 4's w/peerless tweets
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  • lawdogg
    lawdogg Posts: 450
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    If a driver works I just go ahead and epoxy it.
    <3 my 3.1TLs

    I will fix your shifted magnets for free. :)
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