Dual mini ear mics for measurements...

Discussion in 'Calibration Equipment' started by Sonnie, Apr 27, 2017.

  1. Sonnie

    Sonnie Senior Admin
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    Smyth Research debuted their Realiser A16 at Axpona and let me tell you it was amazing. In a nutshell, you can reproduce the sound of any listening room (up to 16 channels) thru your headphones. The demo was amazing to say the least. Thru the headphones it sounded like you were in an Atmos theater.

    But that's not the focal point of this thread. What I am wondering is if there is any reason why we can't use and wear the same dual mini in-ear mics they were using to measure our in room response. They were using them for measuring sweeps... and I see no reason why Herb and Cross-Spectrum Labs could not calibrate a set. Then we would wear the measurement mics in our ears.

    I found these, but I am not sure how you wear them. It looks like the mic end would be in your ear. Smyth Research had a ear sponges with a hole where the mic was inserted to allow them to face outward. I am sure there are some out there... and perhaps I should just contact Smyth Research and ask about what they were using.

    To me ... this would be the idea way of measuring in room response... and with Dirac, you could even perform the entire setup process from your primary listening position and/or multiple positions if you so choose.

    These would probably work with a USB adapter... SP-EBM-1

    upload_2017-4-27_23-37-16.jpeg
     
    #1 Sonnie, Apr 27, 2017
    Last edited: Apr 27, 2017
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  2. tesseract

    tesseract Senior Admin
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    I like the idea of using these for room correction, but you would literally have to put your head in a vice for repeatability. Regardless if one wants to go to that level or not, this would work great.
     
  3. Sonnie

    Sonnie Senior Admin
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    A lot of folks are moving the mic 6" left/right, etc... and even with Smyth Research he had you look straight ahead and then left, then right. Perhaps moving the head around a tiny bit between measurements would be the natural thing to do. However, during the actual measurements, viced all the way... not hard to do really.
     
  4. Tonto

    Tonto Senior Member

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    I'm thinking it would be better to have 2 mics that you could set up about 6" apart at the PLP to mimic your ears. Would take some rewriting of the REW software (I assume). I wonder if that has ever been tried. You bring up an interesting twist for REW. Do you know if he as ever considered measuring with 2 mics at a time?
     
  5. Sonnie

    Sonnie Senior Admin
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    If we have them in our ears, then the measurements will take into account our body and our ear lobes.

    They make these too, which are dual mics:

    upload_2017-4-28_17-56-12.png
     
  6. Everyone's ears are different.
    upload_2017-4-28_20-37-58.png upload_2017-4-28_20-39-35.png
     
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  7. Sonnie

    Sonnie Senior Admin
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    Well as you can see... my ears are clearly not as large as yours.
     
  8. Todd Anderson

    Todd Anderson News Editor / Reviewer/ Senior Admin
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    I wish you hadn't said that Dennis... someone out there is likely to try it. ;-)
     
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  9. Sonnie

    Sonnie Senior Admin
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    Just as soon as I possibly can of course. :bigsmile:
     
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  10. AudiocRaver

    AudiocRaver Senior Admin
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    As Sonnie and I have both said often, "YES, we DO listen with our head in a vise!" Like the car insurance commercial on TV says, If you want the best sound, "It's what you do."

    I think Dennis is probably right, though, repeatability becomes critical.

    Would it make sense to get the basic effect but soften it a little to soften the severity of head position inaccuracy by "softening" or flattening some of the ridges and bends in the ear shape? Or remove the outer ear? Maybe Van Gogh was onto something!
     
  11. AudiocRaver

    AudiocRaver Senior Admin
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    Sonnie and I discussed this by email earlier today.

    We tried two-mic measurements with a few years ago and it did not go so well. Here is the gist of our conversation.....

    ==================

    Two USB mics do not get along well on a Windows machine. Switching between them is not a smooth affair. I don't remember exactly how we tried to do it, but I remember that it was so herky jerky and hard to get REW to recognize the other mic that we gave up on it. pretty fast It was a Windows problem, not a REW problem.

    The mics we were usinig were from ?? XTZ ?? is that right? But the interface was basically the Windows generic USB mic sound driver, the same one that the UMIK-1 uses.

    If we used an analog audio interface with two mic inputs, and had a way to activate them one at a time, like a little mixer (I have one, by the way a little 2-input Mackie), so we could quickly & easily switch between them but only have the one interface with the computer active all the time, that might work. Then the only potential issue is that REW's mic calibration file would have to be the same for both - switching for every measurement is just too many clicks - so the two mic elements would have to be pretty closely matched. That was true of the XTZ mics, +/-1dB. They would have worked if not for the USB switching problem.

    Does any of that sound familiar?

    I think the best use of the two mics in/with ears, then, would be to use left mic for left speaker and right mic for right speaker. Having one's head and body in the picture might be a good thing, not exactly sure. Seems like it would be anyway.

    Then there's the HRTF compensation, which you would have to combine with the mic calibration curve in REW. For headphones, you basically are negating the HRTF because the sound is beamed straight into the ear. For speakers, you normally use a mic with no ears in the equation, but I THINK it would be more accurate by having the head / fake ears there.

    Make sense?

    I guess the first step would be to take the L and R measurements by whatever slow means you can, just to see how it affects Dirac tuning. A second pair of LF sweeps with a UMIK-1 would help you see what is going on in the bass.

    Having Herb calibrate could be tricky - Should he calibrate with or without "ears" present? Not sure.

    Things to think about.
     
  12. Sonnie

    Sonnie Senior Admin
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    I ordered up a pair... I'll take a measurement with my UMIK and then try the in-ear mics. But they are combined measurements.

    If you will remember... Smyth Research had us look straight ahead, then at the left speaker, then at the right speaker. That might be something to try too when taking measurements.
     
  13. It will be very interesting how much variability there is between listeners and between trials with the same listener with in ear mics.
     
  14. Sonnie

    Sonnie Senior Admin
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    That's true.... with your BIG ears, the sound would likely be very distorted for everyone else.
     
  15. AudiocRaver

    AudiocRaver Senior Admin
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    Smyth research: They had signals coming from all speakers at once, as I recall. I made a short video during one of those runs, I'll check it out..So L and R were being analyzed at the same time. That does not mean they were combined. We are not sure what the analysis method was.

    I wonder if they might be of some help with this project. Without giving away any proprietary info. I don't have a contact name or number, you must since you ordered. Think it is worth asking for a little guidance?
     
  16. Sonnie

    Sonnie Senior Admin
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    Well they started a sweep with one speaker and blended to the next to the next, IIRC.

    The in-ear mics would have to be a combined signal in order for us to use it with miniDSP (Dirac), which is what I am after, then of course we could measure the results as well.
     
  17. AudiocRaver

    AudiocRaver Senior Admin
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  18. Sonnie

    Sonnie Senior Admin
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    I could only get one of the dual mics to work. Need a stereo to mono adapter. It will be here Tuesday of next week.

    upload_2017-5-26_0-22-42.png
     
  19. AudiocRaver

    AudiocRaver Senior Admin
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    what are you running it into?
     
  20. AudiocRaver

    AudiocRaver Senior Admin
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    It sounds like you are planning to combine the two mic signals directly in the stereo > mono adapter. This would work with high impedance mics, with some signal loss. If low impedance, then the signal loss will be a lot more, and the combination of the two mic signals could be distorted and inaccurate. Not saying it won't work, just that it is not standard practice with mic signals and might not work, or might give erroneous results. If you want, when I get home I can send you my 2-channel Mackie mixer. You could do some experiments with my 3dio ears also.
     
  21. Sonnie

    Sonnie Senior Admin
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    I am running it into a USB mic adapter.
     
  22. AudiocRaver

    AudiocRaver Senior Admin
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    I guess it is worth a try. Are you following someone's suggestion to use a stereo to mono adapter or is that your idea? I would not have gone that way, I would have used a mixer. but maybe it will work. Following my own philosophy to try the easiest things first, go for it.
     
  23. Sonnie

    Sonnie Senior Admin
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    Yeah... just a hunch that the adapter will mix it to mono in a simple method. Figured it was worth a shot to try it.
     
  24. AudiocRaver

    AudiocRaver Senior Admin
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    fingers crossed
     
  25. Lanion

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