Monitor 5jr weirdness: Tweeter only on one, Mid woofer only on the other!?

charmquark
charmquark Posts: 4
in Vintage Speakers
These speakers are brand new to me. Like, right out of the box. They are 1980s-era, and they're ported - no passive woofer. Starting from when I hooked them up, one of them only plays through the tweeter, the other only the woofer. Swapping sides doesn't change it. Other speakers (several pairs) all work fine with my receiver. So it is definitely the speakers. I have no knowledge base to figure this out. Speakers just aren't what I know. The person I bought them from assured me they were working excellently before being shipped. Could something jiggle loose in shipping? The same thing in both speakers but reversed? It seems a little far-fetched, but I can't for the life of me guess what might be going on.

Thanks for any help!
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Comments

  • F1nut
    F1nut Posts: 50,498
    The mid-driver issue is likely due to a shifted magnet. It's a common issue with vintage Polk mid-drivers that have not had additional adhesive added. The tweeter issue could be any number of issues such as a bad fuse, oxidized fuse ends/fuse holder clips, loose wires or a bad tweeter.
    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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  • charmquark
    charmquark Posts: 4
    Thanks! I've been talking to the seller, and they suggested changing fuses first off, so I've ordered some. For the mid-driver, that's a good tip - I will look for that. I'm hoping it was just some things getting jiggled in shipping. The way my UPS delivery person rolled another package - with a bass amp inside! - up my steps leads me to believe it is definitely possible.
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  • F1nut
    F1nut Posts: 50,498
    You can test the suspect fuse by simply swapping it with the known good fuse.
    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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  • boston1450
    boston1450 Posts: 7,630
    Iirc the fuse is just for the tweeter. You need to do the push lightly in/out test on the driver/woofer. Use 2 fingers so it is evenly pushed in LIGHTLY. If it feels scratchy or frozen it will need to be replaced OR fixed
    ..
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  • boston1450
    boston1450 Posts: 7,630
    The magnet may have shifted like F1 stated above. The lightest nudge/drop or even in shipping may cause shifted magnet. They need to be reglued to help them from shifting again
    ..
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  • charmquark
    charmquark Posts: 4
    So I looked at the mid driver on the one with tweeter only and everything looks tight and solid - no shift. But the driver is still frozen and doesn't give at all when I gently push on it like the other one does. Is there another reason the driver would be frozen? Or can the magnet still be shifted even though everything is pretty tightly together? Here are a couple of pictures:


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  • Gardenstater
    Gardenstater Posts: 4,458
    Most likely the pole piece, which is also called the T Yoke (silver plate on the magnet with the Polk label on it) is shifted relative to the Front Plate (the other silver plate on the forward side of the magnet). It wouldn't be visible necessarily, that it is off center and the magnet is so strong that even if the adhesive has let loose the pieces are held together firmly from the magnetic attraction.

    You can also check to make sure that the spider doesn't have any cracks or distortions in it. That is the orange gauzy convoluted phenolic impregnated cloth suspension. It isn't always easy to see cracks and you may have to really examine it closely while moving the cone. Unfortunately yours is locked up so you can't move the cone.

    Most likely it is shift within the magnet assembly due to adhesive failure.
    George / NJ

    Polk 7B main speakers, std. mods+ (1979, orig owner)
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  • xschop
    xschop Posts: 5,000
    You should be able to pull the magnet and pole-piece off the base plate and basket.
    Don't take experimental gene therapies from known eugenicists.
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  • charmquark
    charmquark Posts: 4
    Well, I am slightly annoyed. I have looked into what is required to fix a shifted magnet and I don't have the setup. Not even close. I wasn't aware it was so involved. Grrr. Guess I'll be forking over some money to someone else to do it. I just can't add another project or time suck to my life at the moment. My instinct was to get a refund and now I'm kinda wishing that's what I'd done.

    That said, thanks for all your help! At least now I know what I am looking for!
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