Ohms at speaker terminals & Ohms at interconnect terminal

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Responses to my earlier question were extremely quick and helpful Thanks to all

Evaluating a potential purchase of used Polk SDA 1a speakers, using a multimeter, what reading of Ohms should I expect at the speaker terminals (my understanding is 4)? And what would be a viable Ohm reading at the interconnect terminals (also 4 ?)

Answers

  • Gardenstater
    Gardenstater Posts: 4,281
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    SDA Handbook is your friend. 3.4 Ohms +/-20% and 10.5 Ohms +/- 10%

    43vb0i55tt6g.jpg
    George / NJ

    Polk 7B main speakers, std. mods+ (1979, orig owner)
    Martin Logan Dynamo sub w/6ft 14awg Power Cord
    Onkyo A-8017 integrated
    Logitech Squeezebox Touch Streamer w/EDO applet
    iFi nano iDSD DAC
    iPurifier3
    iDefender w/ iPower PS
    Custom Steve Wilson 1m UPOCC Interconnect
    iFi Mercury 0.5m OFHC continuous cast copper USB cable
    Custom Ribbon Speaker Cables, 5ft long, 4N Copper, 14awg, ultra low inductance
    Custom Vibration Isolation Speaker Stands and Sub Platform
  • Dede
    Dede Posts: 16
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    Thanks so much for your time and effort to provide the answer to my question. I would love to have a copy of the SDA handbook. I'll do a search and see if there is a copy on the forum-Thanks again-I appreciate your help
  • Gardenstater
    Gardenstater Posts: 4,281
    edited May 2023
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    I can't seem to find the link to rev3 but here is rev2:

    https://us.v-cdn.net/5021930/uploads/editor/fe/zg3wih4m7prz.pdf

    I think it shouldn't be so hard to find.
    George / NJ

    Polk 7B main speakers, std. mods+ (1979, orig owner)
    Martin Logan Dynamo sub w/6ft 14awg Power Cord
    Onkyo A-8017 integrated
    Logitech Squeezebox Touch Streamer w/EDO applet
    iFi nano iDSD DAC
    iPurifier3
    iDefender w/ iPower PS
    Custom Steve Wilson 1m UPOCC Interconnect
    iFi Mercury 0.5m OFHC continuous cast copper USB cable
    Custom Ribbon Speaker Cables, 5ft long, 4N Copper, 14awg, ultra low inductance
    Custom Vibration Isolation Speaker Stands and Sub Platform
  • F1nut
    F1nut Posts: 50,084
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    Dede wrote: »
    Responses to my earlier question were extremely quick and helpful Thanks to all

    Evaluating a potential purchase of used Polk SDA 1a speakers, using a multimeter, what reading of Ohms should I expect at the speaker terminals (my understanding is 4)? And what would be a viable Ohm reading at the interconnect terminals (also 4 ?)

    Reading the resistance at those points does not tell you what the nominal impedance of the speaker is.
    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

  • Dede
    Dede Posts: 16
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    I am not particularly sophisticated in these areas; what would that make a difference? How does one measure the nominal impedance of the speaker and how is that different than the terminals? For purchase purposes
  • skipshot12
    skipshot12 Posts: 1,082
    edited May 2023
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    Impedance changes with frequency?
  • treitz3
    treitz3 Posts: 18,659
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    You can have a speaker rated at 4 ohms nominal (not under load). With that said, some 4 ohm speakers can dip down well below that during heavy demands. For purchasing purposes, you need to look at an amps performance under load (is it a high current amp?), as well as the speakers under a load. It's best just to ask and be patient with/for the answers.

    The thing is, no manufacturer likes to devolve this kind of information. It is mostly found out through speaking with owners, or a "reputation" of a speaker/amp. Case in point would be the Original Carver Amazings. It's rated at 4 ohms but by now, most everyone knows that it can drop down to an almost dead short under load and that dropping down to 1 ohm is pretty common with them.

    Spec's only offer a glimpse of what a system's or component's performance will be like.

    Tom
    ~ In search of accurate reproduction of music. Real sound is my reference and while perfection may not be attainable? If I chase it, I might just catch excellence. ~
  • pitdogg2
    pitdogg2 Posts: 24,921
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    The key word here is "nominal". Which means in use they could by 5.5 ohms or 2.8 ohms....
  • F1nut
    F1nut Posts: 50,084
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    skipshot12 wrote: »
    Impedance changes with frequency?

    Bingo! The nominal impedance is an average or the majority of the range.
    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

  • skipshot12
    skipshot12 Posts: 1,082
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    An example, Infinity Kappa 9’s were rated either a 4 ohm or an 8 ohm speaker from Infinity… don’t remember.
    But, there were two points in its frequency curve that they dipped to 0.8 ohms, a beast of an impedance to drive if one doesn’t have a proper amp.