Rta 12b woofers not connected and barely working

Dr Rick
Dr Rick Posts: 4
in Vintage Speakers
These have been in my family since my brother bought them new. Their sound always seemed a little lacking. I decided to open them up and found that the left woofer on both speakers was disconnected. When I connected them there was barely any movement and no discernible sound. It made me wonder if they were never connected. How could I tell if it needs new crossovers? What else could explain this? Recommendations?
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  • gp4jesus
    gp4jesus Posts: 1,988
    Either that or the VCs are sticky or frozen
    Samsung 60" UN60ES6100 LED, Outlaw Audio 976 Pre/Pro Samsung BDP, Amazon Firestick, Phillips CD Changer Canare 14 ga - LCR tweeters inside*; Ctr Ch outside BJC 10 ga: LCR mids “Foamed & Plugged**”, inside* & out
    8 ga Powerline: LR woofers, inside* & out
    *soldered **Rob the Man (Xschop) LR: Tri-amped RTi A7 w/Rotels. Woofers - 980BX; Tweets & Mids - 981, connected w/Monoprice Premiere ICs
    Ctr Ch: Rotel RB981 -> Bi-amped CSi A6 Surrounds: Premiere ICs ->Rotel 981 -> AR 12 ga -> RTi A3. 5 Subs: Sunfire True SW Signature -> LFE & Ctr Ch; 4 Audio Pro Evidence @ the “Corners”. Power Conditioning & Distribution: 4 dedicated 20A feeds; APC H15; 5 Furman Miniport 20s
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  • CH46E
    CH46E Posts: 3,591
    If you press evenly on the said drivers do the scratch, rub, or make any noises?

    Did you make sure you hooked them up right? I THINK in those speakers the black is positive.
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  • westmassguy
    westmassguy Posts: 6,850
    On the 12 B & C, the two woofers receive power differently. On the left speaker, the left/outside woofer receives its signal from the upper crossover section. The right/inner woofer receives its signal from the lower crossover section. The right speaker is the opposite/mirror image.

    8g8ljuhvmd23.jpg
    Home Theater/2 Channel:
    Front: SDA-2ATL forum.polkaudio.com/discussion/143984/my-2as-finally-finished-almost/p1
    Center: Custom Built forum.polkaudio.com/discussion/150760/my-center-channel-project/p1
    Surrounds & Rears: Custom Built forum.polkaudio.com/discussion/151647/my-surround-project/p1
    Sonicaps, Mills, RDO-194s-198s, Dynamat, Hurricane Nuts, Blackhole5
    Pioneer Elite VSX-72TXV, Carver PM-600, SVS PB2-Plus Subwoofer

    dhsspeakerservice.com/
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  • Dr Rick
    Dr Rick Posts: 4
    The drivers are frozen. 😡. Still seems like it wouldn't be coincidence that the same drivers on both speakers froze. Something I should fix before I replace them, so it doesn't happen again? Also, where do I find a replacement? I searched polk for mw 6501 and found nothing. Some ebay options, but they are originals and I don't trust the longevity or quality.
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  • pitdogg2
    pitdogg2 Posts: 25,576
    It's not unusual actually. The thing is you can also use the mw6600 driver as well. They pop up on ebay more often than mw6501. They are sonically the same. First thing to do is glue up the good drivers. Original JB weld or power grab express heavy duty.
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  • Gardenstater
    Gardenstater Posts: 4,502
    Well maybe the previous owner knew they weren't working and thought that it was best to disconnect them, perhaps out of a lack of knowledge of how a loudspeaker works or fear that there was a short circuit or something. We need Colombo (ahh one more thing.....) to question that guy.

    You definitely want to go with the originals (6501 or 6600X). They really do hold up very well over time, except for the vulnerability to magnet/pole piece shift, probably due to adhesive that wasn't up to snuff. The surrounds seem to last a long long time, being of butyl rubber (maybe neoprene?), which doesn't deteriorate very easily unless the storage conditions are very bad.

    Just ask any eBay sellers whether the voice coils are rubbing or not and ask them to make sure to pack them with lots of cushioning around them.
    George / NJ

    Polk 7B main speakers, std. mods+ (1979, orig owner)
    Martin Logan Dynamo sub w/6ft 14awg Power Cord
    Onkyo A-8017 integrated
    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: 50,654
    Dr Rick wrote: »
    The drivers are frozen. 😡. Still seems like it wouldn't be coincidence that the same drivers on both speakers froze. Something I should fix before I replace them, so it doesn't happen again? Also, where do I find a replacement? I searched polk for mw 6501 and found nothing. Some ebay options, but they are originals and I don't trust the longevity or quality.

    You're not going to find new ones....lol
    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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  • westmassguy
    westmassguy Posts: 6,850
    https://www.ebay.com/itm/154361801427?ul_noapp=true
    Just popped up on fleabay
    Home Theater/2 Channel:
    Front: SDA-2ATL forum.polkaudio.com/discussion/143984/my-2as-finally-finished-almost/p1
    Center: Custom Built forum.polkaudio.com/discussion/150760/my-center-channel-project/p1
    Surrounds & Rears: Custom Built forum.polkaudio.com/discussion/151647/my-surround-project/p1
    Sonicaps, Mills, RDO-194s-198s, Dynamat, Hurricane Nuts, Blackhole5
    Pioneer Elite VSX-72TXV, Carver PM-600, SVS PB2-Plus Subwoofer

    dhsspeakerservice.com/
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  • Dr Rick
    Dr Rick Posts: 4
    I contacted Polk. They, of course, don't make replacements. They suggested these: MW Audio MW-6503-8: 6.5 inch Polk Audio Copy Woofer | Midwest Speaker Repair.

    Turns out the glue on the magnet completely failed on those speakers. Now I need to learn how to repair them. Looks like I would have to take off the cone to get them to line up perfectly.

    Good idea on the JB Weld for the current speakers. Might as well keep them running as long as possible
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  • audioluvr
    audioluvr Posts: 5,603
    edited March 2021
    Dr Rick wrote: »
    Good idea on the JB Weld for the current speakers. Might as well keep them running as long as possible

    That is what we do. Though I have not heard these models, if they are cosmetically good the restoration process is very desirable and satisfying! You'd be surprised at how many really good sounding speakers are tossed because drivers fail, surrounds fail, crossover components fail or just sound like crap! I've restored several old Polks, Infinitys, Klipsch's and Boston Acoustics all of which turned out superb using the knowledge gained from this forum and it's great members!
    Gustard X26 Pro DAC
    Belles 21A Pre modded with Mundorf Supreme caps
    B&K M200 Sonata monoblocks refreshed and upgraded
    Polk SDA 1C's modded / 1000Va Dreadnaught
    Wireworld Silver Eclipse IC's and speaker cables
    Harman Kardon T65C w/Grado Gold. (Don't laugh. It sounds great!)

    There is about a 5% genetic difference between apes and men …but that difference is the difference between throwing your own poo when you are annoyed …and Einstein, Shakespeare and Miss January. by Dr. Sardonicus
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  • Gardenstater
    Gardenstater Posts: 4,502
    That eBay seller is accepting offers (only 3 left!) and the price ain't terrible. Your speakers are more than worth it! There are members here who have repaired them successfully but I would go with the eBay ones and keep yours to repair as spares. Keep us posted and good luck.
    George / NJ

    Polk 7B main speakers, std. mods+ (1979, orig owner)
    Martin Logan Dynamo sub w/6ft 14awg Power Cord
    Onkyo A-8017 integrated
    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: 25,576
    @lawdogg

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  • pitdogg2
    pitdogg2 Posts: 25,576
    Looks like I would have to take off the cone to get them to line up perfectly.

    No you do not remove the cone
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  • lawdogg
    lawdogg Posts: 455
    Dr Rick wrote: »
    I contacted Polk. They, of course, don't make replacements. They suggested these: MW Audio MW-6503-8: 6.5 inch Polk Audio Copy Woofer | Midwest Speaker Repair.

    Turns out the glue on the magnet completely failed on those speakers. Now I need to learn how to repair them. Looks like I would have to take off the cone to get them to line up perfectly.

    Good idea on the JB Weld for the current speakers. Might as well keep them running as long as possible

    Let me know if you'd like to know how to build a jig to re-center them. Or, if you'd like me to do it for you if you wanted to mail them to me, no charge.
    <3 my 3.1TLs

    I will fix your shifted magnets for free. :)
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  • Dr Rick
    Dr Rick Posts: 4
    Hi All. I'm just circling back to this after a few years. I'm about to order the MW Audios and looked here to see your offers to fix them or send me to jig plans. Thank you! Would you send the jig plans and I'll see if I can do it myself? If not, I'll send them to you.
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  • lawdogg
    lawdogg Posts: 455
    In the time since I posted above, I made a how-to guide here: https://forum.polkaudio.com/discussion/197152/diagnosing-fixing-shifted-polk-mw-drivers/p1

    Hopefully that helps.
    <3 my 3.1TLs

    I will fix your shifted magnets for free. :)
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