MiniDSP EARs measurement rig

Discussion in 'Measurement Techniques Discussion' started by dBel84, Nov 9, 2017.

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  1. Hrodulf

    Hrodulf Prohibited from acting as an MOT until year 2050

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    So, it's no poor mans' GRAS... If variability between different types of headphones isn't too horrid, then one might get away by fine tuning the compensation curve until it matches a known well-performing rig.
     
  2. purr1n

    purr1n Desire for betterer is endless.

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    I'll post results from a GRAS, this, and flat coupler for Focal Clear. I've had the data for a while now.

    Will peek into MiniDSP calibration files... Kind of scared to do so. Strong sense of the ChiFi side of the Force. The bad kind of Chi.
     
  3. cskippy

    cskippy Creamy warmpoo

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    I'll be happy if we can find an easy fix, but I don't want to tweak hundreds of values to get compensation curves matched when my flat plate coupler is considerably better.
     
  4. Hands

    Hands Overzealous Auto Flusher - Measurbator

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    I will say this rig has some hilarious results in CSDs due to resonances (as is obvious when you see the impulse response this generates) most of which comes down to the ear canal. And compensation only does so much to help that...

    Marv said it, what, 5-6 years ago, that removing the ear and canal from the equation will get rid of this and likely be more akin to what we hear after the brain filters stuff out. It's true, really. But then I also have to worry about what a flat coupler misses, when looking at it from the other perspective, and I find it fun to get weird with it all an investigate as best as I can with what little brain power and understanding I truly have in this field.

    @cskippy The way I see it, there is no easy way out of this. I mean, the actual enjoyment and listening aspect of the hobby is easy, but I enjoy the dumb complexity of marching forward with new measurement rigs and trying to figure them out, if we can. Then again, I enjoy weird, obsessive, stupid hobbies...I'm sitting here smiling thinking about all the dumb work I'll have to put in to maybe make this work.

    @Marvey here is what ARTA says the MiniDSP-provided compensation curve looks like for my left ear:

    MiniDSP Compensation.PNG

    Pretty simple and standard, it seems. I see their logic given my raw results but still don't entirely agree with it, obviously.

    Oh, and for those of you using REW, does it allow exporting measurements as CSVs and the like? Manipulating measurements, working with compensation curves, and overall crunching numbers is much easier if you have comparative CSV or other spreadsheet data to work with. And turning the MiniDSP-provided compensation curve into a .mic file for ARTA is as simple as using text to columns in excel, removing the data you don't need, copying it into notepad or similar, and saving as .mic. You'll lose what they provide for phase, though, AFAIK.
     
  5. cskippy

    cskippy Creamy warmpoo

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    I agree on all points. The problem with impulse response, distortion, and CSDs can not be fixed by compensation. I'll be eager to see what you come up with though, as you continue to tweak.
     
  6. Hrodulf

    Hrodulf Prohibited from acting as an MOT until year 2050

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    Yup. Go to File->Export and pick what you like.
     
  7. Hands

    Hands Overzealous Auto Flusher - Measurbator

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    Distortion results for me so far have been fine on the EARs rig, as far as I can tell. I have some noise issues in my house that throw off my bass results, but otherwise stuff looks clean and as expected. Impulse response looks super goofy, but, of course, looks fine if you remove the silicone plate and ears and stick the headphones on the flat coupler portion. CSDs look mostly fine with compensation in ARTA, but there are still some resonance artifacts that are clearly caused by the EARs rig itself. I am not opposed to using a dual setup, one for gathering FR and distortion and the other for decay and the like. It's a pain, but if you've seen the amount of effort Tyll puts into measuring one headphone, it doesn't seem so bad. :)

    Again, this is why I'm playing around with the possibility of moving the mics so they're flush with the ear canal opening. I think you either have to do the ear canal right with this sort of rig or almost not at all. Having something in-between, or half-assed like a straight tube opening, seems to harm more than it helps.
     
  8. Serious

    Serious Inquisitive Frequency Response Plot

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    As long as the coupler surfaces are similar and the seal is similar the distortion should be about the same. It's important that the materials are similar enough though. My V1 coupling material gives me about a 5db lower level overall with the HD600 and HD800 (or other open phones, I assume) than the creatology foam + CD one with the same microphone. And from memory this does change distortion results even with the same voltage to the driver.

    Technically you could. You could use a compensation curve and then create an IR from the minimum phase of the compensated curve. Although the dummy head results probably aren't MP, so it wouldn't be quite right. The CSDs use the compensation curve anyway, so no issues there, technically. Although as Hands mentioned the results will not be comparable to flat plate coupler results.


    I'm a bit disappointed by the compensation curve they picked. Looks like even a stock HD800 would look warmer than flat with that curve. Looks brighter than even Tyll's ID curve*. C'mon MiniDSP, it's not the 80s anymore. You can do better than this.

    *Or maybe it's about the same. Sort of in between DF and ID for midrange it seems, which is weird.
     
    Last edited: Dec 30, 2017
  9. Hands

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    Quick update. I moved the mic from the end of the canal to the opening of the canal. Was actually super easy. The mic has tons of slack with its wire and is loosely adhered inside the rig. So, take off the metal cover (4 screws), take off the silicone coupler plate and ear (4 screws), unplug the mic from the board, then feed mic cable through ear and rig until mic is situated where you want it. I think you could even get away without gluing the mic in place, since it's just the right size to be held in place by the silicone canal opening.

    Hardest part was getting the silicone coupler screw holes to line up with the metal plate. Everything else took me maybe two minutes total.

    So, here is my HD650 again, raw results (i.e. no compensation), but with my flush with ear canal opening. This is basically how I do it with my in-ear results.

    It's not perfect, i.e. I still think there's a wee bit of bass roll-off to compensate for, but otherwise this looks pretty damn good as a starting point.

    HD650 Mod Left - EARS rig w mic flush at canal opening RAW.png

    Impulse response looks clean and quick, whereas before it was just constant ringing, and CSDs look uber-clean as you'd expect for an HD650.
     
  10. cskippy

    cskippy Creamy warmpoo

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    Holy crap the frequency response looks worlds better! I'll be giving that a go. Do you mind posting pre adjustment FR for the HD650 if you have it?
     
  11. Serious

    Serious Inquisitive Frequency Response Plot

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    Looks as expected. Would be interesting to see the ones with the ear canal compensated for both HD650 measurements to look the same and see if there are differences with other headphones. I bet there are.
     
  12. Hands

    Hands Overzealous Auto Flusher - Measurbator

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    Mind you, you'll probably have to rip out the adhesive holding the mic in place at the metal plate, and thus may not have the option to return if you so choose. I'm no stranger to voiding warranties on products before thinking things through, so I'm fine with this myself.

    Plus, this doesn't yet solve any imbalances between the two mics. You'll have to sort that our yourself. And we'll still have the question on if we need for further compensate this beyond, say, what appears to be a natural, slight bass-roll off in the mics (and my ADC, slightly).

    I posted raw and compensated results for this HD650 earlier, when the mic was at its normal place at the end of the canal. These results, mic flush at canal opening, are without any compensation. I'm not sure I understand what you're looking for when you say "pre-adjustment FR for HD650," if not the two results I posted earlier in this thread.

    Yes, these results were not surprising. Get rid of their half-assed ear canal, and, yep, looks a lot like what you'd see when measuring with ears and in-ear mics, even without any form of compensation.

    I must be having a hard time today, seeing as I can't seem to make sense of what people are asking. Could you clarify what you mean there at the end?
     
  13. Serious

    Serious Inquisitive Frequency Response Plot

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    Lol, I admit that rereading it, it sounds pretty confusing. I simply meant that we could use these new results without the ear canal as a reference for what the standard ones with the ear canal should look like. Basically create a compensation curve for the ear canal results using these new ones without the ear canal as a baseline. And then look for differences between the uncompensated ones without the ear canal and the ones with the ear canal with the new compensation curve.
    Provided the phones have good channel matching you could even have one ear of the rig with the ear canal and one without and compare them like that without disassembling the rig all the time.

    What I'm thinking is that, in theory, the ear canal results should be more accurate, it's just that we need a good compensation curve for them. The ones without the ear canal are already pretty damn close without a compensation curve. So I was wondering how big the differences would be between ear canal results with a good compensation curve and uncompensated ones with the mic flush at the ear canal opening. Say we create a compensation curve for both HD650 measurements (with ear canal and without) to look the same. I bet there would still be differences with other phones using that same compensation curve. Or in other words, I don't think the effect the ear canal has is the same for every headphone, just as with the outer ear.

    Comparing my measurements and Tyll's with my compensation curve I can still see some differences here and there, even if, say, the Utopia FR would be almost exactly the same. The question is then what is more accurate: A real head with real ears, without an ear canal or a dummy head, with fake ears and a fake ear canal. I'm thinking that a good dummy head would better, but yeah, if the ear canals are really that bad it could be best to just eliminate them.

    In any case, we need more data. Measuring multiple phones on multiple different rigs and looking for the differences.


    In hindsight that was pretty confusing, too. TL;DR:
    Use FR of mic flush with ear canal opening to create compensation curve for the stock rig with the ear canal. Then compare the two.
     
  14. purr1n

    purr1n Desire for betterer is endless.

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    I plan on keeping the ear canal and cocha. Will adjust to see if I can get similar results to the GRAS / Jude's Kemar, which I think has GRAS 45 ears. I like the idea of consistency and accuracy if easily achieveable.

    I like Jude's compensations because they seem comparable to the V2 measurements overall slopewise with some differences here and there in the upper mids and highs.
     
  15. Serious

    Serious Inquisitive Frequency Response Plot

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    Lol, his three Utopia measurements were all over the place. But yeah, the HD650/HD660S results looked good, comparable to the ear canal flush results that Hands posted actually.

    Jude uses the supplied DF compensation, doesn't he? Hmm, DF is pretty flawed I think. DF is so old by now, we need something better.
     
  16. Hands

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    @Serious OK, thanks for clarifying! I see what you meant now. I agree that would be interesting to test. Whether I care enough to do it, seeing as flush canal measurements look like a good starting point to me, is another question.

    In theory, I would like to keep the canal and mic as the rig comes out of the box, but I still have my concerns about how that affects resonances and gain areas that we can't easily compensate for. I'd still be willing to find a way to work around it somehow, but I like the path that has opened up with the flush mic.

    For example, if I leave the rig as-is, out of the box, and apply a compensation curve that tries to get results to look like my usual in-ear measurements, I can get a FR result something like this.

    OK, yeah, it's not exactly like my in-ear measurements. I made the curve earlier and did something a little different when gathering these measurements, but the idea is the same in that it's somewhat along the lines of what you'd see with my in-ear results. This is just with a compensation curve applied on the stock EARs rig. Not using their compensations in any way.

    HD650 EARs dumb compensation.PNG

    But, of course, you get a really fun looking impulse response like this. All the headphones come out looking like this. Not surprising, I suppose. I don't have the knowledge to compensate for this level of weirdness, just basic FR curves.

    HD650 EARs dumb compensation IR.PNG

    Which leads to a CSD result like this. We all know the HD650 is pretty damn clean, with a tiny, tiny bit of resonance around 5KHz that quickly dissipates. This is like the HD650 grew a large time-domain nose of some sort.

    HD650 EARs dumb compensation CSD.PNG

    If there are ways we can compensate for this, I am interested! I'm just too dumb to figure that much out yet.
     
  17. Tyll Hertsens

    Tyll Hertsens Grandpappy of the hobby - Special Friend

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    You get what you pay for, I suppose. Real ear canal couplers have a couple of small tuned chambers in the ear canal to simulate the real acoustic impedance of the canal, and the mic diaphragm is tuned to have the same acoustic impedance of the ear drum. These both damp the ear canal to be more realistic. I reckon they maybe should have forgone the ear canal and just left the jig for on-ear and over ear cans.

    Great work, Tyler. Pretty much what I expected, really. Gonna be interesting to watch this shake out as you guys think about this gadget. I do think it would be great to have a 'standard' measurement rig for enthusiasts. Maybe there's some sort of mod you can do with the right bit of melamine foam in the ear canal.
     
  18. Hands

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    @Tyll Hertsens Putting stuff inside the ear canal sounds like it could work. I don't want to pretend that I know more than I do, so I wouldn't be the right person to determine what would work best in there. I think for my sake at least, the most straightforward path, with some possible sacrifice to better accuracy, is best left by eliminating the canal and keeping the mic flush with the canal opening. I hope someone else is willing to take on this challenge or suggest particular materials for me to try!

    Now, for everyone else, I have been toying around with a basic compensation curve. @Serious inspired me with his custom Innerfidelity compesations, so I was trying to go for something that was somewhat in the spirit of that and somewhat in the spirit of how my older measurements usually turned out. What I'm using for these tests isn't final by any means, and it's quite simple. It's basically flat to about 1KHz, but uses MiniDSP's curve below 25Hz (very minor), and then uses something akin to the B&K curve above 1KHz, a slight and mostly linear slope down.

    Here I took my HD650 and measured it with and without a couple rubber bands around it to simulate more clamp due to a larger head. The EARs rig really just is not wide enough for some headphones, especially something like an HD650 that has been stretched out to dramatically lessen clamp on large heads.

    So, first result is without rubber bands, and second is with rubber bands to simulate more clamp. I personally think the results with the rubber bands more closely match what I hear.

    HD650 Hands Mod Left FR EARs Custom Curve Test.png
    HD650 Hands Mod Left FR EARs Custom Curve Test w rubber bands.png


    I also did the same for the LCD-2C. Bass essentially remains unchanged, as it seems the LCD-2C gets you flat bass no matter what, so long as the seal is good. What does change is some characteristics in the upper-mids and treble.

    Again, I'm inclined to think the results with the rubber bands for greater clamp best match what I've heard.

    LCD-2C Left FR EARs.png

    LCD-2C Left FR EARs w rubber bands.png


    Most of all, I'm curious if anyone else thinks these look fairly close to what they actually hear or not. I am open to feedback, broad or very specific!
     
  19. Tyll Hertsens

    Tyll Hertsens Grandpappy of the hobby - Special Friend

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    I'll mention that when I have troubles with a seal I often use rubber bands to get the pads to mush into place better. I'll put them on and just leave them for a few hours then come back and try again. With rare exception I can get the headphones to seal on the head without them for the actual measurements. My head is a bit small, but probably not as small as the MiniDSP.

    At any rate, I have a lot of experience looking at measurements with and without rubber bands. A good seal without them almost always looks like the headphone with the rubber bands. I've seen very few headphones where the rubber bands added something extra or delivered more bass than I've heard.

    There are exceptions, usually with on-ears, and occasionally with sealed over-ears that have big soft pads and a non-vented ear cup. Usually you just end up with too much bass. If you use rubber bands with non-vented ear cup sealed cans you may have to break the seal with a bit of felt of something to simulate a little hair. The symptom you'll get is no bass, then when you get the seal it comes on hard and fast. I've found I need to split the difference (without rubber bands, just getting a good seal will do it), usually with a small artificial leak.

    I have played around numerous time looking for some sort of resonance from the rubber bands and have never seen anything that looked like I was seeing the rubber bands vibrating. One exception is noise cancelers, which seem to go whacko with rubber bands on them.

    If the jig is small, I bet you're going to find it almost impossible to measure the AT headphones with the wings. They don't have a up/down tilt mechanism on the capsules so you end up with a big gap at the top of the earpad. In those cases I'll put rubberbands around the bass of the headband arches to pull them in...hard.

    Anyway, I think it's fairly safe to use them when you can't get a seal as long as you check what you're hearing against what you're measuring.
     
  20. Biodegraded

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    @Hands if I'm following right, the funky impulse response you were getting earlier was with the stock mic postion, yes? How does it look when flush? The FRs are now looking good, would be nice if your mod improved the CSDs too...
     
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