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Recapping Polk Monitor 10B crossovers

Discussion in 'Speakers' started by transmaster, May 17, 2018.

  1. transmaster

    transmaster AK Subscriber Subscriber

    Messages:
    8,188
    Location:
    Cheyenne, Wyoming
    Just ordered the parts from Sonic Craft to rebuild a set of Polk Monitor 10B crossovers I purchased a few months ago. The replacement XO's I purchased from eBay are in much better condition than the originals were, before their rebuild, on the 10B's now. The originals had been DC blasted by a Sony receiver I once had. I know a great deal more about the subject and My service equipment is a vast improvement. This time I am going with Mundorf MCap EVO's, and Vishay Mills resistors. I am spending 1/2 the money I spent rebuilding the originals.

    There may be problem with the left side XO right now. It's polarity is not right and it may be triggering my Yamaha AVR to shut down occasionally.

    I am going to rebuild these crossers to 10A spec's, the only difference is I am removing and bridging the polyfuse. The polyfuse has a nominal resistance of .5 Ohms so R1 in the 10B is 2.0 Ohms. The 10A which has a 1 Amp fuse R1 is 2.5 Ohms. A 2.5 Ohm 12 watt Vishay Mills is going in. The safety circuitry in a modern audio amp is far better then anything a vintage speaker such as this set of vintage Polks ever had.

    DA5B72AC-61FB-40F8-BDD1-874BD2768F94.jpeg
    Vishay Mills MRA series resistors.
    FD39E30A-63A2-47AB-B476-9719028E045E.jpeg

    These standoffs are much, much better than the originals.

    829589FA-A489-4E72-A50F-E7C358814C9D.jpeg
     
    Last edited: May 18, 2018

     

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  2. StimpyWan

    StimpyWan AK Subscriber Subscriber

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    I've used Mundorf MCap EVO Oils, and they had a long lead and a short lead. I 'assume' one was for the inner foil, and the other to the outer foil. I still don't know which lead was which, and if it even mattered, in a loudspeaker crossover? Hopefully, it won't matter on the Polks?

    Oh yea, Parts Connexion carries Mundorf capacitors too. They're having a 25% off sale on caps, through the end of this month. Grab some more EVO's and speakers. A good time for more projects!
     
  3. transmaster

    transmaster AK Subscriber Subscriber

    Messages:
    8,188
    Location:
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    I looked at Parts Connexion and Sonic Craft is still just a little cheaper on the Mundorf EVO's Sonic Craft also had the Vishay Mills resistor values I needed. I also purchased some Cardas paste soldering flux.

    On Mundorf cap's the shorter lead is supposed the foil side. There is smoldering flame war on this issue on some specialized forums. I would like input from Polkies here in this subject. Certainly the XO's schematic show no polarities on the cap's. These cap's will go in the same way just for consistency.
     
    Last edited: May 17, 2018
    StimpyWan likes this.
  4. transmaster

    transmaster AK Subscriber Subscriber

    Messages:
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    Location:
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    Just read white paper on the subject from Clarity Cap's and according to their research the quality of the manufacturing is the key Clarity says it does not make any difference how they go in.
     
    Drugolf and StimpyWan like this.
  5. StimpyWan

    StimpyWan AK Subscriber Subscriber

    Messages:
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    Location:
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    I've used both Sonic Craft and Parts Connexion. Sonic Craft definitely has better prices on the Mundorf caps. But, PC carries some Mondorf series, that SC doesn't. Though, I can't typically afford those! I did get my Mundorf's tested and matched. I felt a little less anal, in wondering if the caps met spec or not, afterwards.

    Thanks for the heads up on which lead meant what. I appreciate that. I can't tell which is which, now that the caps are installed. But, I did use the same orientation across the various crossover boards.

    Also, good to know that even ClarityCap says orientation doesn't matter. I guess I'm OK then.
     
    transmaster likes this.
  6. transmaster

    transmaster AK Subscriber Subscriber

    Messages:
    8,188
    Location:
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    This is how the XO is going togather, as a 10A

    Schematic Polk Monitor 10A
    1A8914C2-A006-4307-B724-23655C588D5C.jpeg
    This is the 10B, note the Polyfuse.
    B6EBBD2F-3171-4C5D-B6A0-CB904A6A5401.jpeg
     

     

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  7. Drugolf

    Drugolf AK Subscriber Subscriber

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    Hey transmaster, please be sure to post a few photos of your completed crossover if you don't mind.
     
  8. transmaster

    transmaster AK Subscriber Subscriber

    Messages:
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    I plan on it. :thumbsup:
     
  9. Drugolf

    Drugolf AK Subscriber Subscriber

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    Thanks neighbor!
     

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