MiniDSP EARS: Deriving SBAF compensations from MiniDSP files?

Discussion in 'Measurement Techniques Discussion' started by purr1n, Nov 7, 2018.

  1. purr1n

    purr1n Finding his inner redneck

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    I don't remember who asked me for this, but I am finally posting this information. I am hoping that folks with EARs interested in using the SBAF headphone compensation will be able to derive it from the HEQ files provided by MiniDSP.

    https://docs.google.com/spreadsheets/d/1uUqkpD3EJMzpl8FeJbNOkjApvMKAIL3IP8Y1At_ldng/edit?usp=sharing

    See related threads:
    https://www.superbestaudiofriends.org/index.php?threads/calibrating-minidsp-ears-part-2.6880/
    https://www.superbestaudiofriends.org/index.php?threads/minidsp-ears-measurement-rig.5377/

    Here are the deltas of the custom SBAF FR compensations for my EARS to the MiniDSP provided compensations. They are by no means perfect; but I feel comfortable enough running with them now. A few things to keep in mind:
    1. I have no idea if adding back the SPL difference will actually work with your individual EARS. The L and R differentials derived from files provided by MiniDSP were quite a bit different from my L and R and differentials. I am very concerned about this.
    2. One issue I had was to get every headphone to look right, to reflect what my ears are telling me, but this seems impossible. Tweak one thing that makes one headphone's measurement look right, and it screws up another headphone's measurement. These compensations are a compromise and balancing act. At the end of the day, it's good enough and it works given the limitations of the EARS which is a budget product.
    3. Frequency response plots derived from the SBAF EARS compensations will be very different from other plots. The target for perceptual neutral was intended to be a flat horizontal line straight across the graph. It's very important to keep this in mind.
    4. The plots here were derived from multiple measurements of over a half dozen headphones. Because of inconsistencies in the positioning process, I applied weighted averaging of results. Some headphones are more immune to positioning variances. Other less so. Data which I felt was obviously bad was thrown out or re-acquired.
    [​IMG]
     
    Last edited: Nov 7, 2018
  2. purr1n

    purr1n Finding his inner redneck

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    Here was my first test case AFTER the compensations were developed. This headphone I did not have on hand to develop the compensation, so it a good test case. My concern still lie with L/R channel matching.

    ZMF Verite - thick pads.
    [​IMG]
     
  3. Vtory

    Vtory Illogical Spock

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    Great! Did you not correct phase info? Or, just use what minidsp corrected for phases?
     
  4. purr1n

    purr1n Finding his inner redneck

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    Just use miniDSP provided phase.
     
  5. Vtory

    Vtory Illogical Spock

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    Compensation comparison (sbaf vs mine v3).jpg
    (No smoothing)

    Tried to apply sbaf compensation curves to my elex measurements. Because my EARS were surprisingly well-matched between left and right channels (note: I very recently purchased ears), applied marv's delta after averaging left and right.

    Honestly a bit surprised that difference is much less than expected.
     
  6. Denonic

    Denonic Rando

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    Having issues with channel imbalance after calibrating mine to the SBAF compensation. I do have one of the EARS from the latest batch that they just restocked. Will work on it a bit more and get screenshots when I'm back at home.

    Also does the pinna do something weird to the HD800 peaks? They seem to be in all the wrong places on the measurements I've found.
     
  7. purr1n

    purr1n Finding his inner redneck

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    HD800 or anything with angled drivers are going to be super sensitive to positioning. Can you try another headphone?

    How off are the left and right FRs of your EARS? Yeah, screenshots will help.
     
  8. Josh83

    Josh83 Friend

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    My EARS were also from the recent batch, and applying the SBAF compensation through my channels out of whack, too. The difference in the original HEQ in the SBAF spreadsheet is larger than the modified HEQ in the SBAF spreadsheet. Obviously it must've worked for Marvey's EARS, but not mine, which had a smaller initial channel difference.

    The supplied HEQ for my EARS for a HD6XX looked like this:

    [​IMG]

    Applying the SBAF compensation:

    [​IMG]

    What I did from there was take the channel that looked most correct (in comparison with Marvey's measurements of the same headphone with EARS, as well as Tyll's measurements and others), apply that to both of my EARS channels, then adjust the incorrect channel (for example, if you ended up applying the left SBAF compensation to both the L and the R, you would tweak the R) based on the initial differences between the channels. Then I continued to tweak from there to hopefully continue to get it closer to symmetrical.

    Here's the result (apologies for the color switch):

    [​IMG]

    Basically, it just took a little tweaking. But the SBAF compensation is way more intuitive than the supplied one, and it's worth the effort even if the initial application throws off your channel balance.

    Note that you'll need to measure a bunch of headphones (preferably ones known for good channel QC), then try to triangulate your tweaks so that the channels look closest to in balance across the whole range of headphones.
     
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  9. Denonic

    Denonic Rando

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    So here is the supplied HEQ calibration measuring my 58x.
    [​IMG]

    Here is the SBAF compensation:
    [​IMG]

    I'll work on channel matching the way Josh83 suggested, but from the looks of it, My graph still doesn't look close to the 58x you posted above. Maybe I'm calculating it wrong?
     
  10. purr1n

    purr1n Finding his inner redneck

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    Close enough. There are some familiar patterns. It's not unheard of that Sennheiser puts in running changes that alter the FR slightly. Also, the EARS can be slightly different from unit to unit. Because of the high Q resonances, there may be particular sensitivies where a generic calibration based from my EARS won't work exactly die other EARS.

    The best way is to establish a calibration headphone(s) and send it out.
     
  11. Denonic

    Denonic Rando

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    [​IMG]

    Managed to match it a bit better. Just needed to play around with adding a static value difference to push the majority of it up and then adjusting where it looked a bit much. Still looking much better than stock! Will measure some others when I get some time to see how they stack up. Thanks for the taking the time to do this. For people just getting into measurements with the EARS, this is invaluable!
     

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