Frequency Sweeps

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PolkWannabie
PolkWannabie Posts: 2,763
edited April 2004 in Subwoofer Hookup & Bass Management
Doc,

I'd like your ( or others ) comments on the Frequency Sweep graph attached. This is NOT from a sub but from fairly full range towers.

The plot is of adjusted values from 1 meter and from the listening area with 85 db @ 100 hz ( Adjusted ) as the reference.

There several things I find interesting about this plot, not the least of which are that the dip in the 1 Meter graph at 53.1 hz seems to have down shifted in frequency at the listening area and even more curious seems to be the overall flatter response at the listening area then at 1 meter.

Comments ? / Questions ?

Thanks in advance
Rick
HT+ Sunfire TG IV, Dual CG Sig II's, CinePro 1K2, Oppo 981, Audio Technica PL120, Polk SRT's & F/X1000's, Samsung 71" DLP
Post edited by PolkWannabie on
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  • VR3
    VR3 Posts: 29,697
    edited April 2004
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    Is that the RTi12????
    - Not Tom ::::::: Any system can play Diana Krall. Only the best can play Limp Bizkit.
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  • PolkWannabie
    PolkWannabie Posts: 2,763
    edited April 2004
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    Yes it is ... On closer examination it's not just the dip that's shifted but virtually the whole curve is shifted and stretched a little.
    Rick
    HT+ Sunfire TG IV, Dual CG Sig II's, CinePro 1K2, Oppo 981, Audio Technica PL120, Polk SRT's & F/X1000's, Samsung 71" DLP
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  • HBombToo
    HBombToo Posts: 5,256
    edited April 2004
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    left or right or both?

    HBomb
    ***WAREMTAE***
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  • PolkWannabie
    PolkWannabie Posts: 2,763
    edited April 2004
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    The 1 meter readings are one meter out from the left with only that speaker active ... The listening position measurements are for both R & L active.
    Rick
    HT+ Sunfire TG IV, Dual CG Sig II's, CinePro 1K2, Oppo 981, Audio Technica PL120, Polk SRT's & F/X1000's, Samsung 71" DLP
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  • HBombToo
    HBombToo Posts: 5,256
    edited April 2004
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    there is your answer bro. Compare apples with apples. do left near field and then far field then repeat for the right. Now that will make for a very interesting analysis.

    HBomb
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  • PolkWannabie
    PolkWannabie Posts: 2,763
    edited April 2004
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    Unless I'm missing something, the one meter measurements should not be affected by room acoustics etc. Outside where there are no walls would be even better but inside should be sufficient. Given that the idea behind the one meter measurements really is to test the speakers response as opposed to the rooms effect on the speakers response, I would think that whether one or two speakers are playing at one meter would make virtually no difference.

    No ? ... If not, then could you explain your thinking a little more.

    Personally I suspect the dip-shift (if you'll excuse the expression) is more related to distance from the speaker and wave length but that's just a guess.
    Rick
    HT+ Sunfire TG IV, Dual CG Sig II's, CinePro 1K2, Oppo 981, Audio Technica PL120, Polk SRT's & F/X1000's, Samsung 71" DLP
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  • HBombToo
    HBombToo Posts: 5,256
    edited April 2004
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    Originally posted by PolkWannabie
    I would think that whether one or two speakers are playing at one meter would make virtually no difference.

    No ? ... If not, then could you explain your thinking a little more.


    My thinking is you can't compare 1 speaker near field measurement to a far field measurent with 2 speakers. If you compare the nearfield to far field of just the left that would be more meaningfull. Yo me anyway.

    HBomb
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  • Dr. Spec
    Dr. Spec Posts: 3,780
    edited April 2004
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    That speaker is probably too tall for a 1 meter near field.

    Near field tends to reduce room effects, but it might not completely eliminate them.

    If you can find a spot in the room that is truly quasi anechoic in the near field mic location, consider yourself lucky. Try corner loading the speaker at a 45 degree angle and placing the mic at 2 meters and at mid height and see what happens.
    "What we do in life echoes in eternity"

    Ed Mullen (emullen@svsound.com)
    Director - Technology and Customer Service
    SVS
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  • HBombToo
    HBombToo Posts: 5,256
    edited April 2004
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    Originally posted by Dr. Spec


    Near field tends to reduce room effects, but it might not completely eliminate them.


    agreed especially when we are not talking about an omni.

    HBomb
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