Polk SDA umbilical cord

Discussion in 'Speakers & Subwoofers' started by Don_K, Jul 3, 2003.

  1. Don_K

    Don_K Agent

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    My mains are a pair of Polk SDA'a, from 1990 or so. They have an "umbilical cord" that passes right channel sound to the left and vice versa. Now that I've installed an AV receiver and four more speakers... no sub. Should I disconnect the umbilical?
     
  2. JamesCB

    JamesCB Second Unit

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    I'm not quite sure and don't quote me on this. I haven't heard about the SDA series since the late 80's. But, I think that cord must be used with those speakers no matter what. As part of Polk's "Stereo Dimensional Array" set-up, the cord has to do with the the way they produce a stereo image. Not at all sure how it works though. I guess I would try it with and without to see how it works with a surround set-up. Do the speakers work if the umbilical is not connected?
     
  3. Don_K

    Don_K Agent

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    Thanks James,

    The speakers do work with the cord disconnected, but they don't sound "right" -- or at least they don't sound the way I'm used to hearing them. I'll leave well enough alone.

    Don
     
  4. Dennis Gardner

    Dennis Gardner Stunt Coordinator

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    Don,

    Give Ralph Stankowski an email on this question. He has run a number of SDAs in his sytem with SDA-SRS 1.2s currently as his mains.

    His email is [email protected]


    Dennis
     
  5. SVS-Ron

    SVS-Ron Screenwriter

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    Don,

    James is right, you must use the "umbilical". The SDA's worked by having two separate vertical speaker arrays. One carried the normal right (or left, depending on the speaker of course) program material, and the other array carried a limited bandwidth segment of the OPPOSITE channel, but in a lower level, and out of phase. The idea was that your right ear would get an out of phase signal derived from the left channel (but, again reproduced from right speaker). That umbilical carried this "opposite channel signal" to the other speaker's crossover array.


    Why do this? The principle was pretty ingenious. It was done to cancel "aural cross talk" between the stereo channels. Ideally (so the theory went) for the best stereo imaging and widest sound stage (think about headphones for a minute) your right ear and left ear only register sounds from their corresponding speakers.

    BTW You could drop the umbilical but then you would only get the SDA's working as conventional speakers, only using one of each cabinet's vertical arrays. The connector does tend to wiggle loose so you want to be sure to check it now and again (if you get sound from both speaker arrays you are connected).

    I loved these speakers. As long as you sat very close to the sweet spot in your room the effect with many CDs of the day was downright startling with total speaker "invisibility" and a sound stage that often extened several feet on either side of your mains. I got a set of these in 1986 and honestly it's only been recently that I thought their smooth/focused soundfield was surpassed (and only with good multi-channel surround sound). The speaker elements Polk used seemed to be a bit fragile though (I think I replaced half of the 5 drivers in each of mine over time), but if you have some in good repair they are fantastic additions to anchor your home theater up front. Ron Stimpson
     
  6. Jack Gilvey

    Jack Gilvey Producer

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    I agree on the SDA's, great stuff. Never got to own a pair, but was amazed every time I heard them.
     

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