Calibrating MiniDSP EARS Part 2

Discussion in 'Measurement Techniques Discussion' started by purr1n, Sep 27, 2018.

  1. Lyander

    Lyander Too sensitive for SBAF

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    I don't know who needs to hear this, if anyone at all is silly enough to need to, but dampening the inside of the chassis, around the microphones, or on the metal discs that support the silicone slabs will not aid in CSD or impulse response results. Home has been noisy as per usual so some variation in distortion measurements etc., but for the most part anything susceptible to vibrations will still remain wonk AF. You'd be better off building a flat plate coupler on the cheap or saving up for less bad fake pinnae.

    Now if you'll excuse me I have some Dynamat Xtreme gunking up my hair.
     
    Last edited: Nov 15, 2019
  2. Magnetostatic_Tubephile

    Magnetostatic_Tubephile Friend

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    From my experience:
    • It is recommended to measure a particular headphone many times with differing positioning on EARS, since some measurement takes may result in less or even (almost) unpronounced 50Hz and 4.5kHz artificial resonance peaks known to be caused by EARS. ( = As with distortion measurements, the more measurement takes you check the better understanding you potentially gain.)
    • If the measured headphone has some significant issues with decaying/resonance around particular mid/treble frequency, CSD graph would show the behavior anyway. ( = If you know the limitations of EARS well, it is perfectly fine even for CSD use.)
     
    Last edited: Nov 15, 2019
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  3. Serious

    Serious Inquisitive Frequency Response Plot

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    Did you try felt in the fake ear canal and/or around the mic? Obviously depending on the frequency of the resonances the felt needs to be quite thick (and the density has to be right). For in-ear measurements where the resonances are in the 6-15kHz region depending on insertion depth I find simply putting the mic in comply tips to be adequate for how I hear in-ears. I think ultrabike or Marvey might still prefer additional damping inside the tube.
    Since the resonance frequency is less than half (open tube, plus additional depth gained by not sticking in-ears into the ear canal) that for headphones the felt would have to be quite thick to have an effect around 3-5kHz. 10-20mm should be effective, but will obviously need lots of compensation.

    Just a thought. Maybe the resonance isn't entirely from the ear canal in which case that won't really help much. I don't have an EARS - the results were off-putting enough for me not to get one, haha.
     
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  4. Magnetostatic_Tubephile

    Magnetostatic_Tubephile Friend

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    Check the below comparison of two random measurement takes that only happened 22 seconds apart (ZMF Auteur, the same channel, different positioning on EARS):

    [​IMG]

    [​IMG]

    The difference is very obvious around 4.5 kHz. The difference seems to imply that the resonance issue is probably indeed not entirely about the ear canal.
     
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  5. Lyander

    Lyander Too sensitive for SBAF

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    @Magnetostatic_Tubephile Yup, it's easy to know what to look out for in CSD results especially when you have a bunch of well-known headphones in the database to check for consistent trends and to compare to other measurements, but I'm a vain bastard who wants nice looking graphs that can be read standalone; since there doesn't seem to be much to do to compensate time domain issues I just went with brutal mechanical mods, haha. As for FR, I do go for averages of multiple measurements, just that I want to keep single measurements relatively neat since I think you might lose some perspective doing averages considering how position-sensitive many headphones appear to be.

    @Serious I actually moved the mic to be flush with the opening of the ear canal because I didn't have to want to deal with the issues associated with identifying and neutralising resonances borne of that weird silicone cylinder. Oddly it didn't help with impulse response performance, loads of ringing before peak still as was the case before, I'm wondering whether my dicking around might have knocked something loose.

    No IEM measurements, but I wasn't too fixated on those to begin with really.

    There was white sealant or something affixing the mics to the plate, completely covering the rear of the the mic capsules (is that what they're called?) and securing the wires; I made sure to clean up as much of that as possible when extracting them. I replaced it with Dynamat Xtreme just now hoping that'd help with ringing in IR.

    I'm gonna investigate more when I have time. Bit too sleepy and might have the weekend packed, but I'll report back asap when I can be arsed to do more measurements. I have some SBAF-comped squiggles from before I completely eviscerated the EARS so I have a sanity check of sorts. Using RAW comp with the mics flush actually seems to be working out well for me, though it shows things as much too elevated 7~9kHz, and upper midrange looks strangely level.

    For now, sleep. Thanks for the advice! Also good call not getting one, hahaha :)
     
  6. Serious

    Serious Inquisitive Frequency Response Plot

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    Interesting, I guess that means it's related to the ears, too. Maybe the material is more reflective than human flesh, but tbh I expected a real ear to be close to acoustically hard at frequencies in the 2-6kHz band. Maybe it's the geometry of the EARS or there's still some slight damping from human flesh. Ages ago I did some quick experiments that seemed to indicate that there's indeed some damping from the skin.

    I find the CSDs to look very good with my in-ear mic measurements up to 7-9kHz where there's a resonance with every headphone.
     
  7. Lyander

    Lyander Too sensitive for SBAF

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    Screw sleep, it's the weekend. I churned out some quick squiggles of the Klipsch HP-3 and the Sennheiser HD600. Do note distortion sucks butts in terms of actual performance because there's a karinderia/cantina/place where people hang out to drink and talk in outdoor voices just a little bit outside my window so I'm not including it. It's why I usually wait until 4AM to generate measurements when I can be bothered, haha.

    The first two are with the mics flush with canal opening and backed with a congested nose's worth of Dynamat. RAW compensation file from MiniDSP too. Second set of HP-3 measurements is before I decided to disembowel the EARS, stock SBAF comp off Marv's spreadsheet.

    HD600:
    [​IMG]
    [​IMG]
    [​IMG]
    HP-3:
    [​IMG]
    [​IMG]
    [​IMG]
    HP-3 (before eviscerating EARS, SBAF comp):
    [​IMG]
    [​IMG]
    [​IMG]
     
  8. Hands

    Hands Overzealous Auto Flusher - Measurbator

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    I've noticed the ZMF headphones in general are incredibly sensitive, during listening or measuring, to slight differences in placement, angle, clamp, seal, and so on.

    Just to make sure, had you recently placed the Auteurs on the measurement rig for the first results? My thinking is that if you had placed them on the rig, squeezed them a bit to help seal around the ears, measured, and then waited, the change could be due to the pads expanding a bit.

    Otherwise, I would still wager some level of pad compression/decompression occurring slowly over time, even without interaction. It could be enough to suddenly cause the slightest amount of leakage that affects CSDs.

    Or, given their relative weight, how they're built, and stability, they may very well have shifted slightly in some way without human interaction. Angle them in such a way that the center of gravity is thrown off, or if perhaps your rig is not on a totally level surface, that could contribute. (Again, the ZMF stuff is not easy to measure nor particularly stable on a head compared to other headphones.)

    Even if you had them on there for a long period of time before the first measurements, it could be that the headphones conveniently shifted on their own in that 22 second window. You know, it's like how double sided adhesive might seem to be holding something vertically without issue...until it all of a sudden doesn't.

    Either that or some sort of software processing variability. Dunno. I don't use REW.

    I think it would be more telling to put a fresh HD600/650 on there, let them sit for a few days, then do a few measurements with 30 second gaps in between.
     
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  9. Magnetostatic_Tubephile

    Magnetostatic_Tubephile Friend

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    Will try to answer in bullet points:
    • I never apply artificial pressure or use any other means to enhance seal unless explicitely stated. I just position headphones in varying ways (letting them "adhere" on its own), check for any visually visible gaps, and measure. I usually do at least 15 measurements per channel. Of course, slightly different pad compression is always possible given the fact I obviously have to manipulate with the headphone when repositioning (and position always a bit differently.
    • The posted "22 second apart" measurements were not first in the line - they were actually among the last ones from that particular measurement session. Those two graphs are not the only ones that show such difference from that particular measurement session.
    • Indeed, ZMF cans seem to be very sensitive for placement.
    • The demonstrated difference in terms of 4.5k region is something I observed to various degree with multiple other headphones e.g. DT880, HD660S, Verum 1. Not with HD600/HD650 though - those seem to very consistently show the 4.5k artificial resonance.
    I am inclined to agree with @Serious that the dummy outer ears (and the headphone pads surrounding them during measurements) do have at least something to do with this but this is obviously just guessing.
     
    Last edited: Nov 15, 2019
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  10. Hands

    Hands Overzealous Auto Flusher - Measurbator

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    Interesting...Observed on HD660S but not HD600/650? Now that seems odd to me. There is probably a technical explanation for it, but it may be incredibly complex.

    Well, it's not problematic enough to the point where it necessitates a ton of experimentation. But if you do play around with it more and start to dial in on a root cause, I think some of us would be interested in your findings!

    Otherwise, for any publicly shared measurements, it's a matter of showing averaged results or posting 2-3 examples displaying variance. "ZMF Auteur may or may not ring very slightly in this area, listener depending."

    And it could be rooted deep in the headphone/driver designs and materials themselves, stuff that we at SBAF may not have the tools, the intelligence, or the patience to investigate. :)

    Thanks for the clarification!
     
  11. Lyander

    Lyander Too sensitive for SBAF

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    Sorry for the necro, requesting a reality check.

    I've gone back to pushing the mics flush with the ear canal opening and stuffing the back of the capsule with Dynamat Xtreme gunk (trying to undo this was incidentally how I killed the right channel). The difference this time around being that I've taken the screws out because besides possibly messing with seal I worry about the screw heads scratching up pads.

    These are all single-channel measurements, level set by measuring 100dBA full-range pink noise— I do like that the lack of massive resonances in the ~4kHz allows me to push sweeps a bit harder to lower the noise floor.

    I still have to buy a replacement mic set eventually (which sucks bums but is entirely my fault), for now I'm just trying to figure out whether this configuration is feasible. Bit poo that the rig will then be useless for IEM squiggles but I guess I could always save up for a cheapo mic and play with tubes.

    Personally I really like how the upper mids look now compared to stock but think that the treble between 6-9kHz is shelved up by about 4dB too much and that "air" region needs a bit of a push up.

    (Not-exactly-stock) HD600 with very worn out pads:
    [​IMG]
    [​IMG]
    [​IMG]
    [​IMG]

    Very-thoroughly-used Klipsch Heritage HP-3 (with a good seal):
    [​IMG]
    [​IMG]
    [​IMG]
    [​IMG]
     
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