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USB Audio Interface for Impedence Measurement and REW

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  • USB Audio Interface for Impedence Measurement and REW

    I have been using a Behringer UCA222 but one of the outputs crapped out on me. I need something that can be loopback calibrated and has the 2 in 2 out for impedence measurements using the REW impedence jig.

    I then used just my PC headphone out to run sweeps, but just like in another thread a4eaudio 's, I was getting these huge dips between 2-3k in ALL measurements I was taking. I have cabinets almost complete for a new home theater monitor using the FaitalPro 10FE22 and the Peerless DFM compression driver in a SEOS10 so I need some reliable measurements soon!

    Anyone have any recommendations? I have seen a Focusrite Scarlett 2X2 pop up on my local classifieds. Would this be ok? I'm guessing I just need XLR - RCA adaptors to make it work. Has anyone used something like this with REW?

    Thanks

  • #2
    Scarlett 2x2 is ok, but the Windows drivers are crappy. They are better supported on Mac. There's plenty of 2in/2out options that will do the trick just fine as well, however. I use Steinberg UR22MKii which I'd definitely recommend, or there is TASCAM US-2x2 and Behringer UMC202HD among others.

    I'd recommend use of 1/4" jacks for audio, XLR for mics. Doing so will avoid you accidentally putting 48VDC on audio lines, since the phantom power only applies power on the XLR pins. You can buy 1/4" to RCA adapters for a couple bucks if you need.
    "I just use off the shelf textbook filters designed for a resistor of 8 ohms with
    exactly a Fc 3K for both drivers, anybody can do it." -Xmax

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    • #3
      Dips ~2-3k using headphone out? Headphone out is what I use and haven't seen that problem.

      I have the cheap Behringer 202? laying around here somewhere. It was a waste if money.
      http://techtalk.parts-express.com/fo...khanspires-but
      http://techtalk.parts-express.com/fo...pico-neo-build
      http://techtalk.parts-express.com/fo...ensation-build

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      • #4
        So I've figured out that what I thought was a crapped out channel on the UCA222 was actually an RCA cable that was toast.

        The dip at 2-3k I keep seeing is actually there. I did some testing and moved the mic up and down a bit from the tweeter axis and the dip was reduced quite a bit just by moving the mic down an inch or two so that it was closer to being between the tweeter and mid.

        Impedence measurements are still not usable. I think this is why on my two 2-way projects my sims haven't been very close to what I actually ended up with.

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        • #5
          UCA222/202 are known to have horrible cross talk between channels at low frequencies, which will definitely affect the impedance measurement. Upgrade to the UMC202HD or any of the other devices mentioned previously would be well worth it.
          "I just use off the shelf textbook filters designed for a resistor of 8 ohms with
          exactly a Fc 3K for both drivers, anybody can do it." -Xmax

          Comment


          • #6
            Wish I'd known that before I bought it! But, for $30 it is not a great loss. Thanks for the input above, I will probably get something in the coming weeks.

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            • #7
              Originally posted by dcibel View Post
              ... however. I use Steinberg UR22MKii which I'd definitely recommend....
              With respect to this, or the other options you mention...can a USB microphone (e.g., UMIK-1 or Dayton UMM-6) work with these external devices? I know that the non-USB mics have some advantages but if I just spent $100 on a UMIK-1 and don't want to replace that anytime soon, can this work with the UR22MKii with some sort of adapter until I am ready to upgrade?

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              • #8
                You can of course use the USB mic, but not in a 2 channel measurement sort of sense if thats what you're after. Part of the reason 2channel measurement works is that the timing reference for both channels comes from the same clock source, which would not be the case using a usb mic along with a seperate device for the reference channel.

                You could however sell your usb mic for say $50-60 and get an EMM-6 instead and break even on cost.
                "I just use off the shelf textbook filters designed for a resistor of 8 ohms with
                exactly a Fc 3K for both drivers, anybody can do it." -Xmax

                Comment

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