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  • Santa Claus is Coming to Town!

    Ok so I've decided to ask wifey to get me some sorely needed test equipment. I built a speaker but I am unable to do measurements properly.

    What I have is this: A Latop (3 yrs old hopefully with a full duplex sound card) Arta software (gated pinknoise?) and I am borrowing a behringer RTA with calibrated mic (I have the cal data). I want to be able to do Fr and Z measurements.

    So here's the question: What should Santa bring me? Blue Icicle? Also note that the mic is borrowed so i should just get my whole set up software, generator, mic and all. I'd like to keep it reasonable. Any suggestions from Santa's helpers? :p

  • #2
    Re: Santa Claus is Coming to Town!

    If you can somehow squeeze the OmniMic system into your budget I think that you'd be very pleased. I realize this is a lot of money but the system is just so simple to use. And it has enough muscle to test everything most of us speaker guys will ever need.

    No test setup is perfect, but considering it's power and ease of use... I'm really happy with it. Worth every penny I spent.
    ~Marty

    Baby Eidolons
    Sapphos
    Cables (Post #54)
    Other speakers (Post #21)
    Design Thoughts (Posts: 6,10,13,33,35)
    Boundary Augmentation
    Dispersion/Interference

    Comment


    • #3
      Re: Santa Claus is Coming to Town!

      I assume that since it says fft that means it has a gated pink noise generator. Is it easier to use?

      Originally posted by ReissM View Post
      If you can somehow squeeze the OmniMic system into your budget I think that you'd be very pleased. I realize this is a lot of money but the system is just so simple to use. And it has enough muscle to test everything most of us speaker guys will ever need.

      No test setup is perfect, but considering it's power and ease of use... I'm really happy with it. Worth every penny I spent.

      Comment


      • #4
        Re: Santa Claus is Coming to Town!

        The OmniMic software utilizes two types of signals... a swept sinewave and a psuedo Pink noise. The signals can be played from a CD player or from your computer.

        For a typical 1 meter acoustic test of a loudspeaker, you look at the impulse response and can usually see the initial impulse followed by a few milliseconds of silence... then a small reflection about 4 milliseconds after the initial impulse. That would be the floor bounce reflection. The sound takes a longer path when it travels down to the floor then back up to the microphone. About 4 milliseconds longer before it arrives at the microphone. (sound travels approx 1 foot/ millisecond)

        So by cropping or "gating" the inital impulse (and about 3-4mS of silence) and ignoring all reflections from the floor, ceiling, walls, etc... you can perform an FFT to take your measured impulse from the time domain into the frequency domain. Pretty slick math.

        The only problem is that the resulting frequency response will only be valid from about 200Hz to 20KHz. Why no bass? It has to do with the reciprocal of the gated time. Let's say your gated time is 5mS... 1 divided by 5mS gives about 200Hz.

        So next you run a near-field test and it will give you all the bass information. If you feel up to it, you can splice the two tests together for one graph showing 10Hz to 20KHz.

        After only a few minutes you'll be cruising along, taking measurements of every speaker you can get your hands on... just to see how they measure up. And you can include phase in your measurements too with one click. I import raw driver measurements into Jeff's PCD and go nuts simulating dozens of crossovers and slopes. It's amazing how easy it is to optimize both frequency and phase of loudspeakers in the year 2012 as compared with 1980. fun fun.

        I admit that there are other cheaper software/hardware routes for speaker designers, but this system works well for what I need.
        ~Marty

        Baby Eidolons
        Sapphos
        Cables (Post #54)
        Other speakers (Post #21)
        Design Thoughts (Posts: 6,10,13,33,35)
        Boundary Augmentation
        Dispersion/Interference

        Comment


        • #5
          Re: Santa Claus is Coming to Town!

          I am, mmm errr the wife is willing to spend that much, I just want to make sure that at $300 it is the best of the alternatives. (There are alternatives are there?)

          Comment


          • #6
            Re: Santa Claus is Coming to Town!

            Have you seen this...

            http://www.minidsp.com/products/acou...urement/umik-1

            I just ordered one yesterday.
            My RSS390HO 15" sub build

            Comment


            • #7
              Re: Santa Claus is Coming to Town!

              Someone correct me if I'm wrong, but I don't believe the Omnimic system will measure impedance. Of course, all you really need to do that is a high precision reference resistor and some cabling.

              There are "USB measurement mics" out there now, like Mattcc22 linked to. Dayton now makes one too: UMM-6

              Comment


              • #8
                Re: Santa Claus is Coming to Town!

                Originally posted by 1100xxben View Post
                Someone correct me if I'm wrong, but I don't believe the Omnimic system will measure impedance. Of course, all you really need to do that is a high precision reference resistor and some cabling.

                There are "USB measurement mics" out there now, like Mattcc22 linked to. Dayton now makes one too: UMM-6
                Nah, I dont think it does, I'll build a box with resistors. I think I'll just get the omnimic.

                Comment

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