How can I fix these speakers?

speakerfix
speakerfix Posts: 4
edited April 26 in Vintage Speakers
I have a set of Polk audio speakers I enjoy the sound of. Recently had one speaker work fine but start to crackle. The middle part was pushed in and I thought that was the issue but managed to vacuum it back to normal. The other doesn’t make noise. Both tweeters in the box work. Bottom speakers in the box aren’t wired which isn’t something I’ve seen so I don’t know how they work. I tried attaching a video but it will only let me upload pictures.
Please help.

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Answers

  • pitdogg2
    pitdogg2 Posts: 26,915
    Bottom woofers are passive radiators. They work from the back wave of the active mid-woofer to produce bass.
    Does the active woofer move freely? When you place 3 or 4 fingers around the dust cap and push in as evenly as possible do you feel scratchy as it moves?
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  • speakerfix
    speakerfix Posts: 4
    Ok that makes sense. Yes they move freely but do make a scratchy noise.
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  • SeleniumFalcon
    SeleniumFalcon Posts: 4,269
    That sound can sometimes be caused by uneven pressing on the cone. Make sure you are moving the complete cone as a single unit when you press, no one side getting more pressure than the other. If you still hear the scratchy sound this can be caused by either a shifted magnet structure or a voice coil that has been heated sufficiently to cause a warping of its shape.
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  • pitdogg2
    pitdogg2 Posts: 26,915
    Chances are the magnet has shifted a bit. It is a well known problem. There's a fix but it is a very involving.
    The other issue could be corrosion in the pole piece area with the voice coil. Those that have taken the magnet and voice coil apart have documented corrosion between the parts.
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  • speakerfix
    speakerfix Posts: 4
    How would I test for those things. I dont know how to tell if the magnet shifted or not. I searched for videos that show some magnet repair but didn't get a better idea. Does scratchy mean anything? it seems that could be a sign of the magnet shifting. The only thing I know for sure is one measures 3.8 ohms and the other measures 0. I want to try to measure the electronics on the crossovers to see if I discover anything out of spec, but read online I have to take them off the board to get an accurate reading. It should be either new board components or new drivers if they're bad correct?
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  • pitdogg2
    pitdogg2 Posts: 26,915
    edited April 30
    Did you disconnect the wires from the driver before the ohm test?
    If so then the zero driver is cooked.
    The driver measuring 3.8 is in the correct ohm range.

    If you do buy some, before installing them glue the magnets with original JB weld two part epoxy to the top and bottom of the magnets. Craft (popsicle) sticks are your friend.
    Post edited by pitdogg2 on
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  • pitdogg2
    pitdogg2 Posts: 26,915
    edited April 30
    Deleted
    Post edited by pitdogg2 on
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  • audioluvr
    audioluvr Posts: 5,861
    Where are you located? There might be a member here that could help.
    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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  • F1nut
    F1nut Posts: 51,655
    I have plenty of MW6502 mid-drivers listed for sale in the classified section.
    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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  • pitdogg2
    pitdogg2 Posts: 26,915
    F1nut wrote: »
    I have plenty of MW6502 mid-drivers listed for sale in the classified section.

    Get these! ^^^^ F1nut knows how to ship, highly recommend!!

    https://forum.polkaudio.com/discussion/199927/mw6510-and-mw6502-mid-drivers#latest
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  • speakerfix
    speakerfix Posts: 4
    pitdogg2 wrote: »
    Did you disconnect the wires from the driver before the ohm test?
    If so then the zero driver is cooked.
    The driver measuring 3.8 is in the correct ohm range.

    If you do buy some, before installing them glue the magnets with original JB weld two part epoxy to the top and bottom of the magnets. Craft (popsicle) sticks are your friend.

    Yes I did. They were disconnected and removed from the box. I will need to look up a video to do that properly.
    audioluvr wrote: »
    Where are you located? There might be a member here that could help.
    Northern Virginia.
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  • grantza
    grantza Posts: 9
    edited June 7
    speakerfix wrote: »
    I have a set of Polk audio speakers I enjoy the sound of. Recently had one speaker work fine but start to crackle. The middle part was pushed in and I thought that was the issue but managed to vacuum it back to normal. T

    The vacuum was a pretty brave and bold move.
    A friend of mine has a audio shop - repairs to some fancy stuff, replacing speaker surrounds etc.
    When that centre cone has been somehow pushed in, I have noticed they use "Prestik", from Bostik to pull them back out. The Prestik is gently heated to make it very soft and pliable, then gently placed on the centre cone. It is allowed to cool again for about 10mins, then the centre cone is gently pulled out and back into position using the Prestik. It makes sense as one has complete control over the process.
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  • pitdogg2
    pitdogg2 Posts: 26,915
    grantza wrote: »
    The vacuum was a pretty brave and bold move.
    No it's not.
    The dust caps on most of the Polk driver are open mesh, not felt or plastic. It fact you can see right through them to the pole piece.
    Holding the driver in place and a quick on/off is sufficient to pop them right out. We've used this method for dacades.

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