Burst Response! HD800, SR-207, HD650

Discussion in 'Measurement Techniques Discussion' started by purr1n, Jan 8, 2017.

  1. purr1n

    purr1n Desire for betterer is endless.

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    It's not accuracy I'm after, it's precision, consistency, and ability to compare results relatively.

    One cannot extract milliseconds of burst information from the impulse response because the information simply is not there in the impulse response. It's an impulse response, not a burst of sines for several cycles!
     
  2. ultrabike

    ultrabike Measurbator - Admin

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    I'm all for precision, consistency and ability to compare results relatively. This IMO is what proper interpretation of the results along with consistent methodology can yield. This is one of the reasons I haven't change my rat shack measurement rig. It's not necessarily super accurate. But in many cases I can go back and compare current results with previous results. I do the best I can to not f**k up to (as in I avoid the leaky baffle these days). And I got a lot of my ideas by learning from what you've done. I continue to do so.

    As far as IR vs burst information, burst of sines is a visualization tool which may display different characteristics of the system in a more readable way than otherwise. In this sense, results will not be the same. One however may be able to get the burst of sines response from the impulse response. My approach would be to convolve the burst of sines with the IR and that probably should do it.

    To check this out, one would only need to send a burst of sines through the headphone and record, and compare results with convolving the IR of the headphone (obtained using the same coupler and physical method to record the burst of sines), with the burst of sines. Convolution in here means, use the IR as coefficients of an FIR filter, and the burst of sines as the input to the filter. Observe the output.

    @Serious, be careful in over simplifying. The whole linear behavior of the channel (in this case cans mainly) may be in the impulse response. But if that was it, and all could be learned by looking at it, nobody would be doing shit loads of monte carlo simulaitons against IR models of channels to design stuff.
     
    Last edited: Mar 22, 2017
  3. JohnM

    JohnM Author of REW - Rando

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    It is. Nothing else is required to know what the output will look like for any input that doesn't exceed the linear input range of the system.
     
  4. ultrabike

    ultrabike Measurbator - Admin

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    LOL!, I've been an engineer long enough to cut me some slack even in things I feel very certain about. I'm only human.
     
    Last edited: Mar 22, 2017
  5. purr1n

    purr1n Desire for betterer is endless.

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    Doh! I just realized I have all the tools (code) at my disposal.


    Now this would be interesting and save a lot of time! Can I send you data sets for this?

    I only have 44.1kHz IR files (from the exact same coupler) and it should be no problem creating 44.1kHz 10kHz sine wave bursts. It would be interesting to see the results after the burst is put through the FIR filter. This would be an excellent experiment to verify if the IR contains all this burst info!
     
    Last edited: Mar 22, 2017
  6. ultrabike

    ultrabike Measurbator - Admin

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    No problem. Send the files my way.
     
  7. ultrabike

    ultrabike Measurbator - Admin

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    Here are some results with the Stax 2170 system:

    results.png

    Zoom on start:
    results_start.png

    Zoom on end:

    results_end.png

    To make things easier to visualize I could smooth out the samples later. This is sort of raw fully @ 44.1 kHz.
     
  8. purr1n

    purr1n Desire for betterer is endless.

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    Yeah. Upsample them to 176 or 192kHz. You'll get better looking sine waves and information shouldn't be lost.
     
  9. Serious

    Serious Inquisitive Frequency Response Plot

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    Are these from the data in this post? I feel they look sort of similar, especially with how long it takes to "reach the correct level" (which is probably just from a bass hump in the FR). Hard to see at the 44kHz SR. The initial crest does look better here, though.

    We should do an overlay between your images and the simulations UB did.

    EDIT: Nvm, we are comparing 100Hz vs 10kHz here, aren't we?
     
    Last edited: Mar 22, 2017
  10. purr1n

    purr1n Desire for betterer is endless.

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    Yes, exact same data. I sent @ultrabike IRs for both channels since I forgot which side I took the burst recordings from. I also included the Atticus R channel IR, which is side the I used for the recent burst recording. The Atticus burst has the most interesting burst pattern, so I felt it would be a good test.
     
  11. purr1n

    purr1n Desire for betterer is endless.

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    This should be all 10kHz.
     
  12. ultrabike

    ultrabike Measurbator - Admin

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    So, interpolated Stax 2170 results to 176 kHz.

    Full
    results.png

    Zoom Start
    results_start.png

    Zoom End
    results_end.png
     
    Last edited: Mar 22, 2017
  13. Serious

    Serious Inquisitive Frequency Response Plot

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    That looks nice and smooth!
    The picture in post #72 is 100Hz for the SR207, HD650 and HD800, isn't it? The simulation also doesn't look too similar to the ones in the first post.
     
  14. purr1n

    purr1n Desire for betterer is endless.

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    Crap. I got the pix wrong! Those are for 100Hz. The bottom two are 10kHz. Let me fix it!
     
  15. ultrabike

    ultrabike Measurbator - Admin

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    Bonus... Atticus zoom at start (which appears to have a 180 degree phase change deal - corrected in the plot for visualization)

    articus.png

    Note I corrected the phase reversal though to put plot on top of input burst.

    To me it looks similar to what @Marvey had there. The 4th cycle seems to peak:
    Atticus 10k.png

    Note the plots are in reverse polarity from each other.
     
    Last edited by a moderator: Mar 22, 2017
  16. purr1n

    purr1n Desire for betterer is endless.

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    Yeah. This one for the Atticus should be correct. I'll upload the 100Hz files for the Z1R and Atticus tonight in the appropriate post. Let be put up 10kHz Atticus wave.
     
  17. Serious

    Serious Inquisitive Frequency Response Plot

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    The peak ... is that the 6kHz peak in the FR? (Looking at my coupler 3 measurements for the HD800 there's a similar pattern, just that the HD800 has more upper treble (more inital energy).)
    What coupler are these measurements from again?
     
  18. ultrabike

    ultrabike Measurbator - Admin

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    Not sure about the peak being due to a 6 kHz peak in the FR. It likely something else IMO but I could be wrong.
     
  19. purr1n

    purr1n Desire for betterer is endless.

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    Hard to say if the peak on the 4th cycle is related to 6kHz, need more data to make that association. The HD800 also has a 6kHz peak but doesn't show elevated 4-5 cycles.

    The V2 coupler.

    @ultrabike: sending you the 192kHz sample file of the recording so you can overlay.
     
  20. purr1n

    purr1n Desire for betterer is endless.

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    Here is SR-207. It looks most similar to the IR convolution on the bottom.

    SR20710k.png
    [​IMG]
     
    Last edited: Mar 22, 2017

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