Resistance Test @ SDA 1B's - Interpreting the results HELP

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ghosthost
ghosthost Posts: 4
in Vintage Speakers
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Im really excited about my new SDA 1B's. They represent my first pair of decent speakers as a long time (aspiring) audiophile.

After bringing them home I read through the SDA Handbook Ver. 3 (found on this forum) and decided I would carry out a resistance test. This was the only test I could perform as I do not have an adequately powered common ground amp yet with which to power the Polks.

The results were spot on for the Right channel. The left channel had two measurments that were slightly off the nominal results. I am not entirely sure how to interpret these values. What do they mean for the inner working of the left channel? Are caps in need of replacement and if so which one(s)?

I have included a couple photos of the 1B's and the resistance check worksheet with the results.

@ Left Channel: IC PIN#2 to BLACK= lower resistance value than nominal. AND
IC PIN#2 to RED = some resistance measured when none is desired


There is a tonne of knowledge on this forum and a bunch of people who know a lot more about this than I do.

Thanks for any advice,


Ryan.
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Comments

  • Schurkey
    Schurkey Posts: 2,100
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    I would be looking at IC Pin #2 to Red first. Corroded connection? Frayed wire?

    Fix it and re-test.




    What happened to Swauger's comment? Seems to be M-I-A.
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  • K_M
    K_M Posts: 1,627
    edited April 2018
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    Was going to ask the same thing, it just vanished.
    Well as Ken said, one resistance check is simply a wire and a connection at each end, so as Schurkey said, maybe just a connection issue would cause that small bit or resistance.
    The other check that is slighly off is going through 2 drivers and an 2 inductors, so .4 ohm off could easily be within the realm of variance.

    Over time, all of our older polks, we eventually opened them up and re-seated every connection, not sure if anything changed, but not a bad idea as corrosion builds up over time and 25-30 years of time, is a while for an electrical connection.


    :o Although I do think measuring from PIN 1 to PIN 2 should not be Infinity........??

    It should be the resistance of 2 woofers in parallel and the series resistance of an inductor?
    (perhaps I am misinterpreting how the test is done)
    Post edited by K_M on
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  • delkal
    delkal Posts: 764
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    I have never seen a hand held multimeter that would actually read 0.0 ohms for no resistance. There is always some internal resistance in the meter and the ones I have will read 0.5 ohms when the leads are shorted. I would not be concerned with the 0.4 number.

    For the higher reading you might want to try some deoxit in the plug and reposition the probe a few times and take multiple readings. Again this slightly higher reading is not going to stop the speakers from playing and I will bet they sound just fine.

    They will sound better with a crossover rebuild but that is not cheap with the SDA's. Enjoy your speakers for a while and decide what to do later.

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  • Schurkey
    Schurkey Posts: 2,100
    edited April 2018
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    K_M wrote: »
    Although I do think measuring from PIN 1 to PIN 2 should not be Infinity........??

    It should be the resistance of 2 woofers in parallel and the series resistance of an inductor?
    (perhaps I am misinterpreting how the test is done)
    With SDA 1Bs, the two pins are essentially the two channels of amplification--"out" from one pin, and "in from the other speaker" for the other. Unless there's a hole in the insulation of the SDA capacitors, the two pins are entirely separated at DC which is what an ohmmeter provides.
    delkal wrote: »
    I have never seen a hand held multimeter that would actually read 0.0 ohms for no resistance. There is always some internal resistance in the meter
    Meter calibration would fix this.
    delkal wrote: »
    and the ones I have will read 0.5 ohms when the leads are shorted.
    My leads are 0.2. Given a choice, I'd have that calibrated into the meter, but instead I simply "zero" the meter with the leads shorted together any time I'm measuring a suspected low-ohms item. 0.2 ohms doesn't make a bit of difference when measuring carbon-core spark plug wires (2000 ohms per foot, usually more) but it can be important when measuring the primary windings of an ignition coil (about half-an-ohm for GM HEI and similar.)
    delkal wrote: »
    I would not be concerned with the 0.4 number.

    For the higher reading you might want to try some deoxit in the plug and reposition the probe a few times and take multiple readings. Again this slightly higher reading is not going to stop the speakers from playing and I will bet they sound just fine.

    They will sound better with a crossover rebuild but that is not cheap with the SDA's. Enjoy your speakers for a while and decide what to do later.
    The numbers being "off" are suspicious, indicators of a problem especially since the two speakers aren't measuring the same.

    You are right about the crossover rebuild improving performance. VERY recommended.
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  • Schurkey
    Schurkey Posts: 2,100
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    Schurkey wrote: »
    What happened to Swauger's comment? Seems to be M-I-A.
    Never mind. It's in the OTHER posting of this SAME question.

    http://forum.polkaudio.com/discussion/181761/sda-1b-resistance-check-interpreting-the-results-help#latest

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  • ghosthost
    ghosthost Posts: 4
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    thanks for all the input everyone. I am going to explore some of these options once I get my amp situation sorted out. I was fortunate enough to hear them before I purchased them and there were no immediate sound issues as far as I could tell.

    Also, apologies for the double post.
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