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Measuring time delay at listening position for drivers...?

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  • Measuring time delay at listening position for drivers...?

    Do I understand correctly that there is no real "time reference" when using the Omnimic since it's usb? And that because of this, you can't use a loopback time reference and take separate measurments to determine differences in time arrival of 2 drivers using impulse response? The documentation with the Omnimic seems to indicate that you should simply play both drivers with the test signal and take the impulse measurement and look for the impulse peaks (both drivers) to try to align them. Is this the way you guys are doing it, and is it still accurate? This is one of the other main uses for me for my measuring setup (along with FR measurements of course) and I want to ensure this works well before I make a purchase. Elsewise, I'll simply get a mobile preamp and use a calibrated xlr mic with phantom power so I can still use the sound card as a loopback source.

    Thanks!

  • #2
    What I get from the manual is the timing is determined by entering the distance from the mike to each driver. This seems a more time consuming process than the Omnimic producing the pulse itself.

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    • #3
      If you are trying to set up the distance values on your receiver for surround sound, then yes you have the correct procedure. You pick one driver as the reference, then play the stereo sweep track with your reference and another speaker. This will generate two impulses. Adjust the distance on the receiver until the impulses line up. Repeat this procedure for all speakers. Its fairly tedious but works very well.

      If you're wanting to determine acoustic offset between a woofer and tweeter for speaker design, Jeff B has a white paper describing the process.
      Don't waste your money on a new set of speakers, you get more mileage from a cheap pair of sneakers. Next phase, new wave, dance craze, anyways it's still rock and roll to me!

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      • #4
        OmniMic does not directly generate the test signal, so there is no way for it to know how long a signal takes. For speaker design we only really care about relative distances though, so please see my blog post on how I do it, with examples, attached.

        Best,

        Erik
        Distance Assessment via Interferometry Sounds fancy, doesn't it? The first step for me in crossover design is to measure the acoustic dist...

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