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  1. #1

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    Default Inductor DCR Insanity For SDA's

    WARNING: If simple math & basic electronic theory gives you a headache you may want to move on.

    Let's get on with it. So you've been reading DarqueKnight's threads on replacing the stock board level inductors in his SDA SRS 1.2TL's and SDA CRS+'s and the good results he's gotten from doing so using Jantzen perfect lay inductors from Parts Express (Special order) Link to thread and you've gotten the inductor upgrade bug. Well your in luck if you've got ether the SDA SRS 1.2TL's or the SDA 2B/CRS+'s as DarqueKnight has done all the heavy lifting on doing this mod and was kind enough to supply part numbers and a contact person at Parts Express to order the inductors from.

    Now what do the rest of us do who don't have the 1.2TL's or 2B/CRS+'s and want to upgrade there inductors?

    First thing we need to do is find out what inductors are being used in our crossovers, here is a list of the different inductors used in the 4th & 5th generation SDA's



    All other measurements were made by using a common DMM, a fixed current power supply and Ohm's Law for figuring an unknown resistance, R = V / I. Where R = resistance, V = Volts and I = Current.

    So how do you find out what the DCR is, Simply put you measure it. But hold on a minute that may not be as simple as it sounds because you need a multimeter that is accurate to at least 0.01 ohms DCR such as a Fluke 8050A multimeter or something in the range of the Fluke (Big $$$) and no that Radio Shack or run of the mill DMM will not get the job done it just doesn't have the resolution and accuracy needed.

    Now some of you may be thinking "No problem I'll use my LCR meter" that most likely wont work ether because most LCR meters don't measure DC Resistance they measure AC Resistance or what's call ESR or "Equivalent Series Resistance" and is typically larger than the actual DC Resistance. Also there is an inherent problem with using any meter to measure very small amounts of resistance and that is call "The parasitic resistance of the test leads" and is usually less than 1 ohm and needs to be subtracted from the reading you get from your meter.

    Now if you don't have one of those high end, high dollar meters that can measure DCR down to a hundredth or thousandths of an ohm you can buy one ($$$+) if this is not an option for you, you could take them to a shop or a friend that has such a meter to get them measured.

    Now there is a way to measure very small amounts of resistance using any run of the mill DMM, a couple bucks worth of parts, Ohms Law and what's call "4-wire (Kelvin) resistance measurement method" that will give you a very accurate reading with a resolution of better than a millionth of an ohm.

    Ohms Law for calculating an unknown resistance states that if you push a known fixed amount of current through the device under test (in this case an inductor) and measure the voltage drop across the device under test you can calculate the resistance using the formula R = V / I, were R = Resistance, V = Volts and I = Current.

    Let's use a real world example to illustrate this. If we take a 22 Gauge 0.4mH inductor and push 0.100 amps of current through it and measure a voltage drop of 0.0687 volts across it we can calculate the resistance using Ohms Law like this:

    R = V / I
    R = 0.0687 / 0.100
    R = 0.687 Ohms


    If you read DarqueKnight's thread I linked to earlier you will notice that he measured the same inductor with his Fluke 8050A multimeter and got a reading of 0.68 Ohms, How's that for the magic of math.

    Here is a link to a tutorial on how to build the power supply and a video explaining the 4-Wire (Kelvin) method for measuring resistance.

    Simple Low Resistance Measurement

    Now if some of you guys measure the DCR of the stock inductors and post your results here like this,

    0.300mH, 22 Gauge, DCR=X.XXX, Make & Part Number you replaced it with only if you had good results with the replacement.

    I will update the above table, Hopefully we'll get the table filled in so we'll all have something to go by when replacing our inductors.

    Hopefully I didn't confuse or bore the crap out anyone with this.

    Happy Modding.
    "It currently doesn't have a remote because I'm pretty sure my ex threw it out at some point 'cause she's a whore.!"
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  2. #2

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    Nice thorough work gimpod.

  3. #3

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    Tony this is a great idea.
    "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 BP's, upgraded IC Cable, Black Hole Damping Sheet strips installed on back wall behind MW's & Tweeters, interior of cabinets sealed, AI-1 interface with 1000VA A-L transformer

  4. #4

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    Simple yet accurate.
    So as long as you know the exact voltage and the exact current the resistance can be calculated simply by the drop in the voltage.
    The kit was just to make it easier by providing a known amount of current divisible by 10.

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    Tony, this is an outstanding thing you did in your post! Thank you sir!
    Taken from a recent Audioholics reply regarding "Club Polk" and Polk speakers:

    "I'm yet to hear a Polk speaker that merits more than a sentence and 60 seconds discussion."

    "Green leaves reveal the heart spoken Khatru"- Jon Anderson

    "Have A Little Faith! And Everything You'll Face, Will Jump From Out Right On Into Place! Yeah! Take A Little Time! And Everything You'll Find, Will Move From Gloom Right On Into Shine!"- Arthur Lee

  6. #6

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    Do you guys want me to add this to the page?

    Solid work Tony!
    www.Vr3Mods.com ///// www.Version3Audio.com

    "No, that's silly talk. Dude, you can't possibly be this audio dumb so quit the act." - Doro

  7. #7

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    Yeah Trey, I think adding this to your mods page is a good idea.
    Taken from a recent Audioholics reply regarding "Club Polk" and Polk speakers:

    "I'm yet to hear a Polk speaker that merits more than a sentence and 60 seconds discussion."

    "Green leaves reveal the heart spoken Khatru"- Jon Anderson

    "Have A Little Faith! And Everything You'll Face, Will Jump From Out Right On Into Place! Yeah! Take A Little Time! And Everything You'll Find, Will Move From Gloom Right On Into Shine!"- Arthur Lee

  8. #8

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    Posted under "Replace Inductors" and "Schematics"

    http://vr3mods.com/LCSDAUpgrade.html

    :)
    www.Vr3Mods.com ///// www.Version3Audio.com

    "No, that's silly talk. Dude, you can't possibly be this audio dumb so quit the act." - Doro

  9. #9

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    I want to do this sometime. Good info!

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    Thanks Tony. Great info. I thought this was going to be a thread calling us insane for changing SDA inductors.
    "Polk SDA-SRSs are hopelessly out of date both sonically and technologically... I see no value whatsoever in older SDA speakers."~Audio Asylum Member
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  11. #11

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    Wow this would be cool leaving the old CO board intact and using "all" new parts on the Gimpod boards

  12. #12

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    I'm giving this a bump cause I still need the values for the stock inductors for the 2.3TL & 3.1TL. If you want you can send me the inductors if you have no need for them and I'll measure them just PM or e-mail me for my address.

    ~ Thanks gimpod
    "It currently doesn't have a remote because I'm pretty sure my ex threw it out at some point 'cause she's a whore.!"
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  13. #13

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    Quote Originally Posted by gimpod View Post
    I'm giving this a bump cause I still need the values for the stock inductors for the 2.3TL & 3.1TL. If you want you can send me the inductors if you have no need for them and I'll measure them just PM or e-mail me for my address.

    ~ Thanks gimpod
    Tony, I can send you the stock inductors from my 2.3TL's if you still need them. I'll try and get them packed up this weekend.
    "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 BP's, upgraded IC Cable, Black Hole Damping Sheet strips installed on back wall behind MW's & Tweeters, interior of cabinets sealed, AI-1 interface with 1000VA A-L transformer

  14. #14

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    That would be great Fred, PM sent.
    "It currently doesn't have a remote because I'm pretty sure my ex threw it out at some point 'cause she's a whore.!"
    "Peace, Love and ICBM's"
    "50% Why... That's almost half."
    "I know, I'm sick and need help."
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  15. #15

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    Excellent!

    Quote Originally Posted by drumminman View Post
    tony, i can send you the stock inductors from my 2.3tl's if you still need them. I'll try and get them packed up this weekend.
    POLK SDA 2.3 TLS BOUGHT NEW IN 1990, Gimpod/Sonic Caps/Mills RDO-198
    POLK CSI-A6 POLK MONITOR 70'S ONKYO TX NR-808 SONY CDP-333ES
    PIONEER PL-510A SONY BDP S5100
    POLK SDA 1C BOUGHT USED 2011,Gimpod/Sonic Caps/Mills RDO-194
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  16. #16

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    That's great, would love the values for the 2.3tl's, thanks for all your efforts Tony.
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  17. #17

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    Cool thread! Glad I have CRS+'s and the inductors were easily replaced without any calculus!
    Good music, a good source, and good power can make SDA's sing. Tubes make them dance.

  18. #18

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    Quote Originally Posted by gimpod View Post
    That would be great Fred, PM sent.
    Inductors on the way as of today - check your PM
    "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 BP's, upgraded IC Cable, Black Hole Damping Sheet strips installed on back wall behind MW's & Tweeters, interior of cabinets sealed, AI-1 interface with 1000VA A-L transformer

  19. #19

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    Awesome job! Yes, I would like to give this a try.

    For the 2B pin/blade, are the above mentioned inductors all 4 that are used? The .4, 1.250, and 2.500?

    Again, excellent write up....thanks for your efforts.

  20. #20

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    Quote Originally Posted by gmcman View Post
    Awesome job! Yes, I would like to give this a try.

    For the 2B pin/blade, are the above mentioned inductors all 3 that are used? The .4, 1.250, and 2.500?

    Again, excellent write up....thanks for your efforts.
    That's correct.

    The table has been updated to include the 2.3TL's (Thanks Fred and I'll get those inductors back to you ASAP), Now all I need is the DCR of a stock 18ga 1.25mh inductor or someone to send me one.
    "It currently doesn't have a remote because I'm pretty sure my ex threw it out at some point 'cause she's a whore.!"
    "Peace, Love and ICBM's"
    "50% Why... That's almost half."
    "I know, I'm sick and need help."
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    "The best way to enjoy digital music reproduction is to never listen to good analogue reproduction." ~ Kenneth Swauger

  21. #21

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    Man that was fast! Nice work Tony.
    "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 BP's, upgraded IC Cable, Black Hole Damping Sheet strips installed on back wall behind MW's & Tweeters, interior of cabinets sealed, AI-1 interface with 1000VA A-L transformer

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