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  1. #1

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    Default Resistor substitution on SDA2

    I'm ready to upgrade my crossovers on my SDA2 double top tweeters speakers. This might have even been covered before, but I have looked and searched and cant find the answer I need.
    The schematic calls for a 2.7 ohm 5 watt resistor. There are none on Parts express website., only 2.5 ohm 12 watt resistors. can this be substituted in its place, or do I need to search out the exact resistor on another web site?
    Also the poly switch I want to replace with a resistor as well. Can you recommend me a value to replace the poly switch with.
    Any and all suggestion's would be much appreciated.
    Thanks so much

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    Sonic Craft carries the exact value you need.

    That said, you could get away with a 2.5 ohm. Some folks wouldn't be able to tell the difference, others like myself can.

    I found the 0.5 ohm 12 watt works well as the replacement for the poly.
    'Political Correctness'.........defined

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  3. #3

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    Quote Originally Posted by F1nut View Post
    Sonic Craft carries the exact value you need.

    That said, you could get away with a 2.5 ohm. Some folks wouldn't be able to tell the difference, others like myself can.

    I found the 0.5 ohm 12 watt works well as the replacement for the poly.
    ^^^^^^^^^^^
    +1 But they're closed until September 2nd
    Last edited by westmassguy; 08-29-2013 at 04:11 AM.
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    The higher-watt-rating is no problem if you have room for it on the circuit board. A lower-watt-rating could be trouble.

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    Thanks for the info on the resistors.
    One more question. The 750 pf mica and 0.5 uf mylar caps can be removed totally and not to be replaced correct?

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    Quote Originally Posted by emionence1963 View Post
    Thanks for the info on the resistors.
    One more question. The 750 pf mica and 0.5 uf mylar caps can be removed totally and not to be replaced correct?
    Yes to the both you are correct. When using better caps they are no longer needed
    Last edited by pitdogg2; 08-29-2013 at 11:13 AM.

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    Quote Originally Posted by pitdogg2 View Post
    Yes to the both you are correct. When using better caps they are no longer needed
    The Silver Micas can all go, but the .5uf Mylar should be replaced with the same quality Metalized Polypropylene Cap you're using in the rest of the Hi-Pass Circuit. It's a shunt for the resistor. Do not eliminate it. You'll change the voicing of the tweeter if you do.
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    Quote Originally Posted by westmassguy View Post
    The Silver Micas can all go, but the .5uf Mylar should be replaced with the same quality Metalized Polypropylene Cap you're using in the rest of the Hi-Pass Circuit. It's a shunt for the resistor. Do not eliminate it. You'll change the voicing of the tweeter if you do.
    Thanks for the info on the mistake I made on the elimination of the .5uf Mylar.
    I am using the Jantzen from Parts Express. Now I don't see the .5 uf Jantzen at Parts express.
    Will a Sonic Cap 5 uf work instead? I don't see a .5 uf listed on the Sonic Craft web site either. Or am I just dumb and blind?

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    Quote Originally Posted by emionence1963 View Post
    Thanks for the info on the mistake I made on the elimination of the .5uf Mylar.
    I am using the Jantzen from Parts Express. Now I don't see the .5 uf Jantzen at Parts express.
    Will a Sonic Cap 5 uf work instead? I don't see a .5 uf listed on the Sonic Craft web site either. Or am I just dumb and blind?
    5uf is way, way too big. Use the 0.47uf cap from Sonicap. Are you mixing and matching different brand caps in the same circuit?
    I just checked the Jantzen 400 volt crosscap, if that's what you're using. They make a 0.47uf which will due nicely.
    Last edited by westmassguy; 08-29-2013 at 12:31 PM.
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    Sonicaps, Mills, RDO-194s-198s, Dynamat & Hurricane Nuts.
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    Quote Originally Posted by westmassguy View Post
    The Silver Micas can all go, but the .5uf Mylar should be replaced with the same quality Metalized Polypropylene Cap you're using in the rest of the Hi-Pass Circuit. It's a shunt for the resistor. Do not eliminate it. You'll change the voicing of the tweeter if you do.
    that is what i get for reading too quickly. I should of asked if it was across a resistor
    thanks WMG

    wouldn't either one of these work.
    http://www.parts-express.com/pe/show...number=027-206

    http://www.parts-express.com/pe/show...number=027-906

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    Quote Originally Posted by pitdogg2 View Post
    that is what i get for reading too quickly. I should of asked if it was across a resistor
    thanks WMG

    wouldn't either one of these work.
    http://www.parts-express.com/pe/show...number=027-206

    http://www.parts-express.com/pe/show...number=027-906
    Yes, either will work, but you want to stay with one brand, Dayton or Jantzen if possible.
    Home Theater/2 Channel:
    Front: SDA-2ATL
    Center: Custom Built http://www.polkaudio.com/forums/show...hannel-Project
    Surrounds & Rears: Custom Built http://www.polkaudio.com/forums/show...rround-Project
    Sonicaps, Mills, RDO-194s-198s, Dynamat & Hurricane Nuts.
    Pioneer Elite VSX-72TXV, Carver PM-350

    "So is there any tread left on those tires or is it just like throwing a hotdog down a hallway?"

    www.dhsspeakerservice.com

  12. #12

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    Quote Originally Posted by westmassguy View Post
    5uf is way, way too big. Use the 0.47uf cap from Sonicap. Are you mixing and matching different brand caps in the same circuit?
    I just checked the Jantzen 400 volt crosscap, if that's what you're using. They make a 0.47uf which will due nicely.
    I am not trying to mix caps if at all possible.
    If you guys are telling me to use the Jantzen 0.47 uf cap then that what I will get.
    Man I am so grateful for the response's, I am receiving. This upgrade is no small coin, as I don't have a lot of money to burn.
    Thank God for this site and all the members here helping me get through this upgrade.

  13. #13

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    Some of my caps came in today. So I decided to pull apart first the speaker that was always sounding less than the other in volume.
    And I found these caps in the crossovers
    I cant believe that someone would put these junk caps into a Polk speaker. Cap values are correct, but the volts are not even close.
    On with the mods.

    Click image for larger version

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    Click image for larger version

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    Those look very familiar!!! Those caps probably cost 15-80 cents each when these were built. This is why I do upgrade these first if it is a speaker I'm going to keep for a while. I'm actually trying the same caps w/ Sonicaps for the tweets, in a CRS system I'm rebuilding. I can't wait to hear your impressions once they burn in.

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    Quote Originally Posted by emionence1963 View Post
    I cant believe that someone would put these junk caps into a Polk speaker. Cap values are correct, but the volts are not even close.
    Those are the stock crossovers with stock components, used to save money to make the speakers more affordable to the regular joe. Remember that the components you are buying will be much larger for the same value, and you will have to work to make them fit on the same board; make sure you use plenty of hotglue/zip-ties.

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    Quote Originally Posted by emionence1963 View Post
    Some of my caps came in today. So I decided to pull apart first the speaker that was always sounding less than the other in volume.
    And I found these caps in the crossovers
    I cant believe that someone would put these junk caps into a Polk speaker. Cap values are correct, but the volts are not even close.


    Attachment 89638

    Attachment 89639
    Those are the stock caps in the pics, what Polk used. They were probably the best available at the design price point when they drew up these speakers. Modern film caps and resistors are so much better, you're gonna love the upgrade when you complete the Xover mods and get everything burned in.
    "Science is suppose to explain observations not dismiss them as impossible" - Norm on AA; 2.3TL's w/sonicaps/mills, polyswitches removed, Lg Solen inductors, RD-0198's, MW's dynamatted, Armaflex speaker gaskets, H-nuts, brass spikes, Cardas CCGR binding posts, upgraded IC Cable, Black Hole Damping Sheets (3" strips) installed on back wall behind MW's & Tweeters, interior of cabinets sealed, AI-1 interface with 1000VA transformer

  17. #17

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    Quote Originally Posted by emionence1963 View Post
    Some of my caps came in today. So I decided to pull apart first the speaker that was always sounding less than the other in volume.
    And I found these caps in the crossovers
    I cant believe that someone would put these junk caps into a Polk speaker. Cap values are correct, but the volts are not even close.
    On with the mods.

    Attachment 89638

    Attachment 89639
    Typical Polk Crossover my friend. The Yellow Mylars were about the best back in the day, but still needed a little help, that's what the little silver micas were for. Electrolytics are cheap but do the job, and are still used widely by all mass market speaker companies. Your new caps will be larger, especially if your replacing the NP Electrolytics with Metalized Polypropylenes. To make some room, you can relocate the resistors to the bottom/copper foil side of the circuit board. It will free up a lot of room. Try to avoid using hot glue. Use 3M VHB tape under all the caps, nylon wire ties, and get yourself a bottle of brush-on Cyanoacrylate (super/crazy glue). Use it whenever two caps are bundled or up against each other. Most of all, take your time, and have fun.
    Home Theater/2 Channel:
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  18. #18

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    WOW ok so they are stock. I thought that somebody else was in there replacing the caps already as the binding post is different than what was originally on them. At least this side. Also this speaker that I am doing right now was a tad duller than the other.
    50 and 100 volt cap? All I can say is WOW!

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    Quote Originally Posted by emionence1963 View Post
    50 and 100 volt cap? All I can say is WOW!
    Are your speakers seeing more than 50V? I want to see the math...

  20. #20

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    Hi Zingo,
    I just finished redoing crossovers exactly the same as yours and just posted some pictures of
    the process in this thread:
    http://www.polkaudio.com/forums/show...nature-Upgrade

    Hope it helps a little if you need it, and if you have any questions I'm happy to help.

    Chuck

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    Well for today, I just installed one set of caps in one speaker. At first I did not notice any difference. But listening for the last 3 hours since the install, there is a noticeable improvement every where. Highs mids lows. I am not going to upgrade the other till the resistors come in, as its too much work to keep pulling the crossovers in and out. Best to make this a one shot upgrade. Just the way it sounds right now I could be happy.
    Pics of the caps I used
    Name:  IMG_0988.jpg
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