What source test tones to use for listening position measurements?

Discussion in 'Archived Threads 2001-2004' started by Wes Nance, Mar 2, 2002.

  1. Wes Nance

    Wes Nance Stunt Coordinator

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    Hi,

    I remember reading somewhere, maybe on the AVS forum, that it was recommended to use sine waves for near field measurements, and warble tones for listener position measurements.

    Can anyone comment on this?

    Using warble tones, my response with the RS SPL meter from the listening position, corrected on my Stryke 12.3 sub is:

    1862.0

    2066.5

    2266.5

    2573.0

    2874.0

    31.573.0

    3672.5

    4072.5

    4573.0

    5071.5

    5670.5

    6369.5

    7173.5

    8075.5

    8973.5

    10072.0

    11170.0

    This is with my mains set to small and my Denon receiver controlling bass management. Everything looks pretty good, but with a 8db drop at 20hz. I have the PE plate amp with default, which has been modeled to be down 3db at 20hz, so I'm thinking of setting the boost to 3db at 20hz-24hz setting on the amp (fb is 21.5hz or so) to bring that back up. Will this work? These are my first measurements with the sub in the corner and the PR's sealed well. . .

    Any suggestions? I was going to get a BFD eventually, but maybe I don't need one for now?

    Thanks

    Wes
     
  2. Patrick Sun

    Patrick Sun Moderator
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    Actually it's:

    Use sine waves for measuring subwoofer response, and use warble tones for measuring full range speakers.
     
  3. BruceD

    BruceD Screenwriter

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    Warble tones are also useful when locating the best bass xover frequency between a sub and main speakers.
     
  4. John E Janowitz

    John E Janowitz Second Unit

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    I get asked by people many times which tones they should use to measure their systems. It really depends on what you are measuring for.

    Some may disagree with me on this, but if you want to setup and EQ your system, you will most likely want to use a combination of the two. Sine waves will excite standing waves in the room, allowing you to see how your room reacts. Many people use the sine waves to find their room modes, and then pull down the peaks, boost dips, etc, and this works fairly well.

    However there are not a lot of true sine waves in the majority of music and movies out there that will excite standing waves the way a 30sec sine wave will. In some cases by just using the sine waves you can over compensate for standing waves that will not be excited the same way with regular program material.

    The warble tones, on the other hand, are constantly changing frequency which helps to keep standing waves from affecting the measurements. This is also not ideal because you won't excite the standing waves as much as your typical program material would, so you will not be able to adjust or EQ enough to help out.

    That is why I try to do measurements with both sine waves, and warble tones, and try to come up with a medium between the two.

    The other time you would specifically want to use warble tones is if you wanted to just try to measure the anechoic response of your subwoofer or speakers. For this you would want to eliminate the effects of the room as much as possible. This is why most people suggest the warble tones for nearfield measurement.

    John
     
  5. Vince Bray

    Vince Bray Stunt Coordinator

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    A side note, and let me say I am no expert, but I noticed the levels you're using are in the 70db range. Somewhere I read that the RS meter is more accurate in the 80db range, and I definitely can confirm that the readings are very different when you go to the 80db setting on the meter. I don't remember which way it was skewed, but I got what seemed like much better readings at 80. If memory serves I had some 6db variances between the two settings.
    Also you might want to go to 2hz increments for the whole range, as some peaks are only 4-5hz wide, at least that's what I ran into in my room. For instance, at 85 you could have a large spike that you're not seeing.
    Believe me, though, at .02 you're probably not getting a great value [​IMG]
     
  6. Wes Nance

    Wes Nance Stunt Coordinator

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