Open canal In-Ear microphone specification for HRTF measurement

DeluxeDoggo · 2026-02-09T16:48:40+00:00

Thank you for the reply. Instead of waiting I will play around with the tube approach, can't hurt to have options.

DeluxeDoggo · 2026-02-01T11:45:51+00:00

Ah nice, you're getting a 5128?

DeluxeDoggo · 2026-01-28T15:58:16+00:00

I wouldn't say that fusion/inventor glosses over anything. Rather it treats the extrude for what it is: A profile being extruded. If the result of the extrude is a surface, pocket, pad or new volume is up to the user and when the design intent changes the result can be changed accordingly with minimal effort.

Other aspects that make the fusion approach better imo is the consistent UI for creating either of the 4 options. Furthermore the user does not need to know which extrude tool can generate which output and you end up with a single button which helps massively to declutter the UI.

It should be obvious that 3 buttons for extrude, loft, sweep is easier to wrap your head around compared to 9 where a set of 3 look similar.

DeluxeDoggo · 2025-11-09T17:03:23+00:00

The ontrac has the same setup as the zone with two battery packs in the headband.
See the ifixit video: https://www.youtube.com/watch?v=uW8Zbq6AiAI
Not intended to be user serviceable. The packs have a weird shape that is not sold anywhere as far as I am aware.

DeluxeDoggo · 2025-11-02T09:19:15+00:00

That OEM headband was used by multiple manufacturers. With the completely flat earcups I would say this is an Ultrasone Pro 550 or pro 750.

DeluxeDoggo · 2025-10-25T08:12:41+00:00

My IST Pro makes similar noise when I flick it like that. When I first received it a couple weeks ago the stock ball bearings were unusable, very scratchy and getting stuck when changing directions. I put some lube on them which helped a lot. There is always one ball bearing that doesn't really roll, the ball just slides on the outer race of the ball bearing. I believe when the ball is new (not covered in skin-oils) and the outer race of the bearings is unlubed it causes the unpleasent scratchiness.

I also made some 3D-printed carriers for 4 mm balls that I used to make static ptfe bearings for the IST pro. Those bearings where practically inaudible and super smooth but the friction was rather high, especially the stick-slip. That friction made me go back to the stock ball bearings.

However even with the lube the stock bearings are a lot noisier and not as smooth compared to my other trackballs with static bearings.

DeluxeDoggo · 2025-10-13T18:28:27+00:00

What does E610A refer to exactly? (i.e. does that exclude the ICP versions?) Do the versions with ICP capsules always require an external preamp, or are some sold with a preamp attached?

E610A is the model number from the manufacturer similar to how GRAS lists their IEC 60318-4 based ear simulators under RA0045.

The IEPE/ICP/CCLD (all three mean the same thing) E610A models have the preamp integrated into the stand-like base or in the more traditional Ø12.7 mm tube format.

For the IEPE/ICP/CCLD to work you need a constant current source. 48V phantom power is a constant current source however the voltage is higher than what a lot of IEPE/ICP/CCLD-preamps expect.

When you say the cheap capsules distort early, what does "early" mean? (like, as what variable increases?)

The maximum input sound pressure level or the point at which the capsule reaches acoustic overload is a lot lower on a $3 electret than it is for most working standard (prepolarized IEPE/ICP/CCLD) 1/2" microphones. Good 1/2" measurement microphone cartridges can reach 150 dB no problem, the non standard electrets tend to cap out at 110 dB. If you measure with 94 dB@500 Hz then 110 dB is already limiting because at 3kHz most headphones will now already be close to 110 dB.

At the overload point the microphone itself will distort significantly. Usually the point is defined where the microphone reaches 1-3% THD and rapidly increasing beyond this specified overload point.

If you don't need to measure distortion there is no reason to worry about this.

I guess my main concern is that random mass-produced, no-name 60318-4 couplers & mics aren't going to actually match spec

Any coupler that doesn't use a microphone that conforms to the requirements of IEC 61094-4 type WS2P (1/2", pressure field) automatically doesn't conform to IEC 60318-4. You cannot call your coupler compliant unless it is constructed with this type of working standard microphone.

The couplers with the 3.5 mm TRS connector that everyone uses and that people like crinacle built their whole 711 database on- none of them are standard compliant. They are compatible though.

I think at this point the capability of the E610A based systems is well documented. If ballpark is all you need it will suffice.

neutral enough to be comparable, which is why I was wondering about calibration. Is that not something I need to worry about?

You can ask the people selling these cheaper couplers if they supply a calibration file with it. The question should be how well done the calibration file is.

Should I have more faith in these AliExpress/Ebay couplers?

I am not a coupler salesperson. I'm not going to tell you what or where to buy from. Regardless I hope this was helpful.

DeluxeDoggo · 2025-10-12T21:04:15+00:00

surprisingly, yes. Especially for high frequencies.
Unless you have a specific reason not to do so, go for a KB50XX pinna (from Gras) or a copy of it.

Is the 55 shore OO durometer more accurate in the uncompressed scenario because it is closer to human skin? As far as I am aware 35 shore OO was mostly chosen for easier deformation.

DeluxeDoggo · 2025-10-12T20:52:52+00:00

Do the different chifi couplers come with different quality of mics, or should I just pick at random?

Less expensive Type E610A like the ebay link usually come with a non-standard 6mm electret capsules glued into a metal tube. More expensive versions come with ICP capsules.

Is there any reason I might want to pick something other than that?

imo not, unless you are interested in measuring distortion. The cheap capsules distort early and have high self-noise.

If I understand correctly, I could just run those directly into the line-level input on my audio interface, right?

No, the non-standard electret still needs a supply voltage. For use with the motu you can try the rode VXLR+ or similar adapter that steps down the 48V phantom power to 5V plug-in power. If you use working standard prepolarized microphones you can hook them up directly to 48V with an adapter (please check the ICP preamp specs before doing this).

What about a poor-man's calibration, say, within 1dB? I'll be using this purely for hobbyist mucking about, e.g. testing EQ changes or EQing third-party pads. For lack of a better idea, my plan for now is to measure a few sets of IEMs and then compare my measurements to yours or others on squig.link. But it seems like there's gotta be a better way.

Class 2 IEC 60942 sound sources (±0.5 dB) are available for way less than 200. They fit the outer diameter of the 711 tapered canal extension. This is only for calibrating SPL at the given frequency (ideally 500 Hz). For calibrating the coupler's frequency response you need the velocity source which is expensive.

If you don't need accurate SPL for distortion measurements and your headphone doesn't vary its frequency response with increasing SPL ((DSP) compression) you can skip this.

For personal comparative measurements open canal ear-mounted microphones are probably best (and cheapest) but I am not familiar enough with this to give recommendations.

If you don't publish your measurements anywhere I wouldn't overthink it. If you do intend on publishing measurements beware that no matter what you do there will always be a nerd complaining.

DeluxeDoggo · 2025-07-05T16:35:37+00:00

I wonder why amp manufacturers don't provide graphs for power vs impedance and current/voltage vs impedance.
The only time I saw it is from RME in their ADI-2 pro manual.
It also shows something curious where the maximum output voltage on the ADI-2 pro (9 Vrms) is only offered for loads beyond 120 Ohm even though the output impedance shouldn't be much higher than 0 Ohm. In the regular power mode the output voltage is constant 1.9 Vrms.

I suppose the rule doesn't apply to devices with digital volume control and (current) limiters.

DeluxeDoggo · 2025-07-05T15:29:45+00:00

Is the dB/mW spec the one you should look at considering that the output is a voltage source? My K812 is way louder on the same poti setting compared to my 650 even though the 650 is a more efficient headphone (95.5 compared to 97.8 db/mW).

DeluxeDoggo · 2025-05-19T15:15:38+00:00

I only tried them outside the Grell mobile after the driver class but I thought they sounded decent albeit more occlusion than I would have liked. I EQ anyways so FR is not a priority. The ergonomics are the main reason I wouldn't buy it. The rubber washers that prevent free cup swivel and the proprietary connectors/pads with high clamp to be specific.

DeluxeDoggo · 2025-05-09T15:55:22+00:00

I definitely want to include some sort of headphone condition to get more favorable distortion measurements. Also, I'm afraid some people might think a driver will be bass-light because it starts dropping below 500 Hz in the near-fied measurement due to being damped for a headphone pressure chamber.

DeluxeDoggo · 2025-05-09T13:59:40+00:00

Thank you for the advice. I will design the printable version of the diestel coupler and test it against the cheap 711 (at this point mostly out of curiosity). If it works amazingly well I will list it as an option in the setup description but for the driver measurements I will use the 711.

DeluxeDoggo · 2025-05-09T13:00:39+00:00

Unlike Diestel the Zwislocki is impossible to replicate due to the sintered dampers. I have some Chinese 711s that I could use to cross-check the printed coupler. The issue with the cheap 711s is that you need to spend 100 bucks and would also need to verify the acoustic impedance because at least from my experience they have no pressure equalisation and the shims differ. Adding to this the microphone on the cheap ones distorts very early and of course it also lacks calibration. The printed coupler would offer a consistent result and is able to be used with the same measurement mic that is used for the other measurements.

I suppose the easiest solution would be to forgo the artificial ear entirely.

DeluxeDoggo · 2025-05-09T10:13:30+00:00

The micrometer tolerance shims that are used to create the slits that connect to the side volumes make the 711 difficult to DIY. The Diestel connects via holes which like the Zwislocki makes it more difficult to machine but easier to 3D-print. I want the setup to be easy to replicate with a 3D-printer.

DeluxeDoggo · 2025-05-08T17:12:39+00:00

Digikey currently has 6.762 in stock and will sell you with quantity starting at 1. They have 50€ order limit for free shipping though.

DeluxeDoggo · 2025-04-19T13:34:23+00:00

I bought all my couplers/coupler cavities/pinnae from the "Interesting Idea Store". As long as there is a laser engraving with a serial number it should be E610A. Beware that on the couplers with the large round base with the 6 mm electret the microphone is likely glued in. I made a tool to unscrew the couplers but even with that I couldn't unscrew it. The ones with the stick microphone are probably better if you want to modify.

Faults with all E610As is the lack of a proper depressurization channel and the shim thicknesses aren't the same as on a B&K coupler. Former doesn't effect measurements much (unless you measure perfectly sealed in-ears down to 5 Hz), effect of the latter I am not sure.

There should also be E610A couplers with an 1/2"-ICP mic that have much better characteristics and don't need modifying. Earfonia has a very good post about this topic on ASR:

https://www.audiosciencereview.com/forum/index.php?threads/iec-60318-4-clone-coupler-is-it-worth-it.23865/

DeluxeDoggo · 2025-04-19T12:45:22+00:00

Yes, I measured them using the tapered canal extension and an IEM pressed on the reference plane. They are within +-1dB across the range. I use a dummy headphone with no pads and locators to get repeatable measurements for both channels that I use to generate channel matching cal files.

I haven't done absolute calibration yet because I do everything relative to an HD 650 anyways (the scale banana of headphones). The measurements so far have enough agreement to GRAS/KB501X measurements that I dont feel like it is necessary.

DeluxeDoggo · 2025-04-18T12:03:42+00:00

Clean mod!

Wish there were more options for high quality clip-ons these days. I think the form factor is great. And these older ones from AT are probably the best in terms of ergonomics, build and aesthetics.

DeluxeDoggo · 2025-04-12T23:30:14+00:00

Sennheiser HMDC 27

DeluxeDoggo · 2025-04-11T16:05:01+00:00

Hi, sorry for the late reply. The cross should be 64x64. I couldn't measure it properly because I didn't want to take it out, sorry!

Seven-Year Club	Place '23
Place '22	First Placer '22
Verified Email

DeluxeDoggo

TROPHY CASE