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Having a hard time finding a straight answer on measuring speaker reading or asking.

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  • Having a hard time finding a straight answer on measuring speaker reading or asking.

    When you measure a speaker down to say 800Hz or less do you as a general rule of thumb aim the mic at the tweeter or the woofer in a 2-way. Also 1m is the recommended distance? I ask since most people listen to speaker farther away, and you will get a different response farther away.
    On the cheap diy. That is my motto - www.hifiposse.com

  • #2
    You aim the mic at a 90 degree angle relative to the speaker, and you measure from at least two meters away, preferably more. When it's a multi-way speaker if you measure too close the wave fronts from the various drivers aren't yet integrated. Speakers are typically rated for sensitivity at 1 meter, but that doesn't mean you measure at one meter. You measure from further away and extrapolate the result to one meter.
    www.billfitzmaurice.com
    www.billfitzmaurice.info/forum

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    • #3
      That helps out, but do I aim at the tweeter or the woofer on a 2 way system.
      On the cheap diy. That is my motto - www.hifiposse.com

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      • #4
        Almost any (normal) "measurement" mic will be omnidirectional, meaning that where you "aim" it won't be that critical. What IS critical is how the sound from your drivers (on your baffle) radiates out into space. This makes where you PLACE the mic the critical thing. (Unless you've got a very "odd" use planned) your mic should be on what's referred to as the "design axis", which almost always means straight out from the tweeter's center (normal to the baffle). At THAT position, what you measure/model will then be representative of what you'd get if you also listen to the final speakers "on-axis" (meaning you've got them "toed in" - , so . . . pointing directly toward your seating position).

        IF you'll end up NOT toeing them in (say they're "in-wall", or on shelving or for some other reason WON'T be toed in, but will be used parallel to the wall), THEN it could be acceptable to measure them "off-axis", the angle "off" being determined by your actual listening geometry. ALL this is only true IF you're going to take FR AND PHASE measurements w/the driver's mounted on YOUR baffle, in a box positioned the same as in its final use.

        MANY people measure ALL drivers on-axis, and generate "minimum phase" files, THEN using software (like JB's "PCD" and the other tools he's created) along with driver's offsets to simulate baffle step, room gain, and diffraction. Using THAT method also allows you to generate FR data SIMULATING any off-axis use that you want (which can also, then, simulate what's called "power response".

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        • #5
          Originally posted by hobbyhands View Post
          When you measure a speaker down to say 800Hz or less do you as a general rule of thumb aim the mic at the tweeter or the woofer in a 2-way. Also 1m is the recommended distance? I ask since most people listen to speaker farther away, and you will get a different response farther away.
          It may depend on why you are measuring. If you are measuring a 6.5" 2-way on a relatively narrow baffle, it doesn't make a whole lot of difference,( if the x-over is more or less finished), and you want to see the results. The response should be virtually the same with a 6" difference in the height of the mic at a meter away, or more. If you don't have the x-over worked out, and are measuring, and planning to use software to design one, then the relative distance to the mic makes a difference. Draw a triangle on paper, and calculate the lengths. One leg is longer than the other. The further away the mic is, the less the difference in leg length. The software takes this into consideration while designing the x-over.

          If you are not good at geometry, get some string, and hold the ends about 6" apart. Then, at the other end of the string, compare where they meet as you move them around.

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          • #6
            Originally posted by hobbyhands View Post
            That helps out, but do I aim at the tweeter or the woofer on a 2 way system.
            Usually on the tweeter axis, as it will probably have narrower dispersion than the woofer. However, with adequate distance it won't matter. If you know what the listening distance will be then for purposes of getting the best result at that distance you'd measure at that distance. Never one meter, with the possible exception of a studio nearfield monitor.
            www.billfitzmaurice.com
            www.billfitzmaurice.info/forum

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            • #7
              Depends what you are doing with the measurement. Jef'f B's guide has the most concise recomendations

              http://audio.claub.net/software/FRD_...0to%2010Hz.pdf

              For crossover design measuring on the listening axis is correct. Many prefer measuring on the tweeter axis as it's easier with design software, and for remembering 5 years later what you did.
              John H

              SLS-85, BMR-3L, Mini-TL, BR-2, Titan OB, B452, Udique, Vultus, Latus1, Seriatim, Aperivox,Pencil Tower

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