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Etymotic ER2SE - A Reference Headphone for your Ears and Your Couplers

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  1. hakuzen
    lolol, that's the spirit. i second this. always skeptical but open minded, and contributing with what you can. this is an small step by us, but it can turn into a big jump for humanity.. errr.. for audiophile world.
    any grain of sand, even any thought, feeling, or discussion, does matter
    toranku likes this.
  2. antdroid
  3. Slater
    My imm6 rig is not worth it. I plan on getting an IEC setup, at which point I would join the tour.
  4. durwood
    I would be interested, same boat as slater though. Still have no idea how to get an IEC coupler out of Taobao to the US though so anyone that can help send me a PM.
  5. Slater
    Agreed. I’m in the US too, so we could even split shipping.
  6. csglinux
    I have two spare 711 couplers lying around that I don't need. I'm willing to donate them to worthy causes, but note the caveats in advance:

    1) The calibration files I'll send with these will mean they'll almost perfectly match my own results. How boring will that be!?

    2) Both couplers are permanently Frankensteined with condenser mics, so you'll need a soundcard with an XLR input that can supply 48 V phantom power, otherwise you'll just have an interesting-looking paperweight.

    I'd already offered one of these to @SilverEars, so I'll give him first refusal. Otherwise, first-come, first-served basis.

    I don't need paying for them, but if anybody wanted to help me cover shipping costs from California, that would be much appreciated.
  7. durwood
    @hakuzen mentions rough cost and an agent to get a coupler only, I browsed through superbuy and get 5 pages of couplers...arg which one? $75 is affordable.


    antdroid mentions that he has the same one as hakuzen, crinacle, etc. It would be nice to get the same one, but if they are all close I am not sure I want the exact one given the next bit of info below.

    hakuzen mentions he uses the AWA6161 type which if my browsing is correct is ~$645 US with the mic. Cheaper than BK and Gras, but still too expensive for me. Is that correct? If so

    I have a m-audio fasttrack pro I used in the past with my ECM8000 mic to provide the 48V phantom, I might take you up on the offer of the coupler, but if the goal is to try and have different ones compensated to flush out any differences, I am still willing to purchase my own and let someone else have a crack at it. On the other hand it would be nice to not invest in yet another piece of measurement gear. I would definitely cover shipping costs on one of them, and do the same for someone else if I move on or want to find something different. I don't currently have a blog, website or provide reviews at the moment, but would provide graphs to share with the community.

    Over the years of measuring audio related things I have at my disposal today:
    1) WM61A capsules (first gen of measurement ideas before there were affordable mics)
    2) ECM8000 mic with fasttrack pro for phantom power
    3) Dayton IMM6 + tube coupler + smartphone + fftplot (IOS iphone 8) / audiotools (android HTC10)
    4) Dayton UMM6 + tube coupler + TrueRTA/ARTA/REW (current method)
    5) Dayton DATS (useful for impedance measurements, never tried an IEM with it though)
    Last edited: Jun 20, 2019
    hakuzen likes this.
  8. csglinux
    I mailed out those two spare couplers I had to @SilverEars and @Slater. Sorry @durwood :frowning2: For now, you are destined to try something else in the name of science and help us flush out those differences.

    @McMadface - no pressure on you here to finish up any ER2SE measurements by this weekend, but... I had a thought. It would be awesome if we could persuade @jude to join our little tour and provide us a reference set of measurements from the headfi lab. I know he's super-busy with CanJam right now, but maybe if we corner him together at the event and ply him with alcohol? A set of measurements from a pro rig would be a huge help. He may want to use his new hi-re coupler, which would certainly be interesting, but I'd actually be more interested to see his standard 711 coupler measurements.
    CoiL, antdroid, hakuzen and 2 others like this.
  9. McMadface
    @csglinux I finished up with the measurements sometime last week and they're ready to send out. That'd be awesome to get @jude on board and I wouldn't mind buying the first round. :beerchug:
    hakuzen likes this.
  10. McMadface
    So, @csglinux and I had a chat with @jude at CanJam SoCal over the weekend. Good news is that he's interested in participating. Bad news is that he'll be busy for awhile, at least until CanJam London is done.

    Also, please welcome @oratory1990 to the thread, who has also expressed interest in participating in the European leg of the tour.
    hakuzen and antdroid like this.
  11. antdroid
    It's getting serious now with all these folks in the mix. :)

    Is there some sort of travel plan for these set up? I think I am next on the list, but who do I send to afterward?
  12. csglinux
    Great to meet @McMadface at CanJam :) But sad we had so little time :frowning2: I spent all of about 5 minutes rushing through the measurements of the MH755. I hope I did it justice.

    Welcome to the group @oratory1990!

    A few things for us to consider...

    As @McMadface mentioned, @jude has graciously agreed to join the tour, but as anticipated, he's swamped right now and won't be able to get to this until end of July at the earliest (after CanJam London). The good news there is that gives us plenty of time for @antdroid to do some measurements and maybe even for us to find somebody else on this side of the pond to join the tour before we mail these IEMs off to headfi HQ and then Europe. (@SilverEars - you interested in joining?)

    I mentioned to @McMadface that GRAS have kindly offered to loan me an RA0402 "hi-res" coupler to test out. This is a couple of weeks away, but I'll probably take them up on the offer. Maybe I can schedule this after @jude has done his measurements and that way he won't be on the hook for the international shipping fees to Europe. These hi-res couplers are certainly interesting, but I'm a little concerned about the fragmentation of standards. The RA0402/0401 is supposed to be backwardly compatible upto 10 kHz, but from what I've seen, it's not. It adds a very strong (14 dB) attenuation to the half-wave resonance which can affects peaks near 10 kHz and can affect THD down as low as 3 kHz. @jude mentioned something very interesting to us at CanJam, which is that Brüel & Kjaer are coming out with their own "hi-res" coupler, which will (of course!) be different again from the GRAS "hi-res" coupler. The B&K version will apparently be good up to 24 kHz and is based on medical imaging scans of 40 Scandinavians (Danes, I believe?) and so likely to be more representative of a true average of the human ear anatomy than the (seemingly random) decision of GRAS to damp a resonance mode that is insertion-depth dependent. The problem then is we'll have vinyl-tube couplers, 711 couplers, GRAS hi-res couplers, B&K hi-res couplers, and an almost certain guarantee that no two measurements in the world will ever agree again. Dan Clark (Mr. Speakers) made a comment at the CanJam AMA that every current measurement rig gives different results. Another depressing fact - even the GRAS RA0402/0401 only specify an accuracy of +/-2.2 dB, which could be fairly significant in comparing measurements from different rigs, even when using the same equipment and measuring the same headphone unit. As a result of all this, I have some thoughts, suggestions, questions, requests, etc., about how we might proceed with all this.

    Somehow we have to make our measurement data available to one another. Some of us may end up using different couplers with different impedance/Q-values and resonant volumes so we can't guarantee a perfect match to every other headphone, but a solid starting point would be if we each supplied the data on these two sets of IEMs (ER2SE and MH755). This way, any one of us could match their results (at least to an average of these target headphones) to those of anybody else in the group. I think the easiest way to do that would be to simply have everybody upload their measurements. I think individual posts on this forum would be the best place to host these data files and then I can simply link to them in one big indexed list from the first post. I like REW, but others may be using ARTA or something different entirely (@McMadface suggested Excel format). We could perhaps let a users' preferred format be discretionary, but also mandate a universal format that everybody can read, such as simple 2 or 3-column ASCII, uploaded in a post that contains a description of the measurement rig used.

    In an ideal world, I think we'd all want to ensure the following:

    1) That we've all used a common, or similar, SPL for measuring. (I typically use 95 dB for FR and 80 dB for THD.) This is probably not critical for FR, but some headphones' FR shifts a bit with SPL.
    2) That we've either performed a loopback-calibration for our driver/input sound-card/analyzer combo, or confirmed that both input and output are ruler-flat (i.e., confirmed that we don't need one).
    3) That our source driver has a sufficiently-low output impedance that it isn't skewing the recorded frequency response. This shouldn't be an issue for the ER2SE or MH755, but it could be for other IEMs.
    4) I don't think any of us need to see anybody else's sound-card calibration files, but it might be interesting to see any mic calibration files used (or to upload both uncompensated and compensated data), to see how much of a nudge that particular coupler/mic combo required to produce the final measurements. (Because we know we can all perfectly match anybody else's data with a suitable compensation curve.)

    Does it even make sense to try and converge on a reference target FR for our final measurements? We could try to define one as some giant average of all our measurements, but on the other hand, it's unlikely our target measurements are going to form the basis of any new international headphone measurement standard :wink:


    P.S. Sorry @castleofargh - you got bumped even further down the queue. And with no foxy young chicks to show for it :frowning2:
    hakuzen likes this.
  13. hakuzen
    great, @csglinux !

    if @jude already owns his old GRAS coupler, it would be a great help for us if he provides measurements using it, besides of the new GRAS rig.
    old GRAS coupler measurements would be a reference for us, who use iec711 couplers. and we'd also get a real sample of the differences between old and new GRAS coupler measurements.

    about format of files, guess all the programs allow import/export to text/csv/excel formats (columns of data basically, easily interchangeable), so any of these formats (and proprietary format, optional) would be great.
    but take in count the problems about "." and "," kilo and decimal delimiters. got some issues when dealing with this at REW. guess we'll be able to manage this after first tries.

    about SPL, i use 94dB both for FR and THD, because it's easier (less work than changing for different measurements) and because if i use lower SPL, i have to increase preamp gain in the soundcard (more difficult to set levels with my EMU-0404, and more distortion added; also check next paragraph). so i'd prefer to keep same SPL high enough for both measurements, if possible. please teach me about the convenience of that low SPL for distortion measurement.

    about source and ADC -soundcard- calibration, found slight differences when using different output volume, mostly related to lows and highs roll-off. they are tiny, but being perfectionist, made different calibrations for different outputs. for example, made them for 5, 10, 15, 20, 25, 35, 50, 75, 100, and 200mVrms output, for each sample rate, because iem measurements use to fall into this range; for sources measurements i use higher voltage calibrations: -10dbV (316mV), dBu (775mV), dBV (1V), 6dBu (1.546V).
    then, after adjusting SPL for the particular iem, i check the result output volume/voltage, and use the according calibration file. i don't know if this is really worth it. the difference in lows roll-off is minimum, but highs roll off difference can be notable if output volume is very low:
    FR calibration 192 - diff mV.png
    note that at 10kHz, 5mVrms output has got -3.1dB!, 10mV -1dB, 15mV -0.6dB, 20mV -0.4dB, 25mV -0.3dB, 30mV -0.2dB. you can also notice the increment of distortion due to higher gain of the preamp.
    there are some sensitive and low impedance iems that only requires 5-10mV to reach 80dBSPL. so taking this into account may be important, and it's another reason to aim for higher SPL, imo.

    another particular reason is i use loud volume (above 90dBSPL) when listening to music (yea, i know there is a risk about this..).

    about sample rate, i use 192kHz 24 bits (0-96kHz sweep) because i don't want to have to repeat the measurements when somebody asks for ultra high response. this is not necessary at all, because usual response at these frequencies are below ambient noise, and the error of our rigs is huge. but guess that 96kHz (0-48kHz sweep) doesn't hurt to anybody, and can help to calibrate our gear if we have top quality measurements from the guys with top gear as reference.
    Last edited: Jun 26, 2019
  14. castleofargh Contributor
    talking of loopback calibration, I redo that from time to time, or just depending on what I measure. mostly because I'm slightly paranoid and got used long ago to re-calibrate things on a regular basis even if the last 10 times nothing had changed. last time I got some weird curve, which to anybody with half a functioning neuron would have immediately meant that a compensation curve was applied. but to me it meant like 10mn trying different cables, using different dummy loads, checking that I wasn't routing the signal through some DSP(as I always do by default with headphones). and only after going slightly mad, did I think of the obvious calibration file that shouldn't be there. :disappointed_relieved: the only time I feel that dumb is when I tweak my EQ by a tiny amount, just to notice later that it's bypassed. something that happened to me way too often for my self esteem to be fine.
    anyway, beside the self trolling, I mention this because some amps may not react the same in a direct unloaded loop compared to when plugged into a 10ohm IEM. usually it won't matter, just like usually we won't really need a loopback calibration for the stuff we measure. but on a few amps it could affect the response significantly. like if the amp has protective caps at the output, or is some no negative feedback stuff without actually offering a valid alternative(although the amp would then logically have high impedance and be invalid for this use anyway), or simply if the amp distorts or clips way too much with some low impedance loads...). so the unloaded loop may or may not be a reassuring effort. I'm playing super-paranoid-dude here, as I said most of the time the differences won't be worth mentioning. but it could be different. I don't really have a solution to offer beside everybody procuring various dummy loads and making more tests than most people need to do to get an amateur FR graph. but then next thing we know we'll be checking temperature and humidity before each measurement and I have no wish to get down that road when using amateur gears. we're always somewhere between "hey, everything is somewhat wrong anyway so why bother?", and "do controlled measurements properly or don't bother".

    about what to pick as a reference, my position is that it doesn't matter so long as we all use the same for this particular effort. all units, all targets are by nature arbitrary, it's the fact that we can consistently refer to it that make their value. so I'm fine with anything you guys wish to use. I was even fine with crinacle's stuff as reference despite the 8kHz controversy, just for the sake of people being able to find their IEM in his database. so anything is fine for me.

    about SPL, I'm between a rock and a hard place. because my mic clearly doesn't appreciate high output in term of THD, but at the same time, I almost always have some noise and vibrations in my room(subs being the loudest). so any IEM that can actually remain close or below 1%THD(so 40dB below signal or lower)in the low end, doesn't really get a chance at 80dB SPL. things are better with my fanless crap computer but only slightly as I placed my actual computer in bunker to reduce fan noises as much as I could. also now REW makes a distinction between THD and THD+N, and the step response can also help a bunch, but it can't do magic and simply remove the constant crap I have. so basically low SPL THD will give excess low end THD, while high SPL will give excess THD in the midrange ^_^. I need to stitch 2 measurements together like a photoshop expert if I want to show something that would approach Jude's THD graphs. giving yet another reason to name my rig, Frankenstein's rig. so again, pick your poison, it won't really fit my needs no matter what :wink:.

    and again, I'm fine if I those IEMs reach me in 2050. I don't have a personal need for a calibration, you might have noticed that even though I spent a lot of time making some for all my mics and couplers over the years, I tend to post graphs that are clearly wrong and obviously so in the low end. anytime I post graphs for the purpose of showing something specific(usually a difference caused by whatever), I remove even my own default calibration(a mix of Jude's ER4SR graphs and the one in the certificate, both stopped at 8kHz so that I don't apply mindless changes in the trebles). I remove it on purpose so that the result looks too wrong for people to be able to spam them somewhere as a false argument about a given IEM. if they did, anybody who actually measured that IEM or saw measurements of it would likely see that something is wrong and easily reject my graph and the false interpretation made from it. yes I'm that wicked. :imp:.
    so really I'm glad to participate to add my own stuff to the data so we get, if not an actual standard, at least enough samples to see where the typical variations occur and let people learn that for themselves when they try to interpret graphs.
    hakuzen likes this.
  15. castleofargh Contributor
    on one hand it's irrelevant because nobody has gears to properly measure above maybe 10kHz, sometime less, sometimes a little more with actual standard couplers. on the other hand, setting things to more than 44.1kHz can very much avoid getting the impact of some weird DAC's filters on the graph. so I'm also advising to use that(and set the DAC at the same sample rate if necessary), even if realistically people shouldn't look at those upper frequencies in the first place.
    hakuzen likes this.
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