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Recommendation for Ear simulator kits for IEM measurement

Earfonia

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I've had several discussions with local Singapore brand of In-Ear Monitor, kind of a small startup company, about In-Ear Monitor measurement. Since this is for formal publication of their measurement, we prefer not to use 'brand-less' IEC 60318-4 coupler kits from China, but a more 'proper' IEM measurement kit. Any recommendation for any proper 'budget friendly' Ear simulator kits for IEM measurement?

Will G.R.A.S 43AC kits a good choice for them?
Any idea how much would be the GRAS 43AC-S4 Ear Simulator Kit?
https://www.gras.dk/products/ear-simulator-kit/product/789-gras-43ac-s4

Thank you!
 

Matias

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bigjacko

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Is EARS a good measuring rig for headphone and iem? I have seen people talking about the acoustic impedance problem, so every headphone would have different flat frequency response.
 
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Earfonia

Earfonia

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I haven't tried it for headphones, but for IEMs it is definitely useless for the following reasons:
1. Poor seal between the silicone ears and the microphone. Basically it fails to function as occluded-ear simulator. To measure IEM the mic and the ear canal must be sealed to simulate human ear canal and the ear drum. EARS white silicone ear mold just sit on the mic without proper seal.
2. I highly doubt the distance and volume of the ear canal for IEM measurement are compliant to IEC 60318-4.

So from my experience I cannot recommend EARS for IEM measurement.
 

briskly

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Stuart Yaniger goes by SIY here. You may as well pose questions and comments at him directly.

As for the problem of acoustic Z, cavity volume is part of that problem, most apparent below 500 Hz. I am not inclined to think that it makes too much of a difference compared to the missing side resonators that would simulate the middle-ear resonance.
You should be able to check the impedance calibration of the drum simulator using a compact condenser mic as the source. I've never done that myself as I don't have the mic stockpile around.
 
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Earfonia

Earfonia

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Cool! Thanks for the reference!

You should be able to check the impedance calibration of the drum simulator using a compact condenser mic as the source. I've never done that myself as I don't have the mic stockpile around.

That I would like to know how. Any link for the impedance calibration method? Thank you!

Greetings to @SIY ! I hope you could guide us some tips for industry standard IEM measurement that doesn't cost a bomb.
Friends of mine starting an IEM brand, they actually already started, and they want to do a more serious and better measurement for their future IEMs. They are working on a few new models now and hopefully they can use better measurement equipment for it. Now they are looking for what best bang for the buck industry standard IEM measurement gears. Thanks!

This is the brand:
https://www.symphoniumaudio.com/
 

briskly

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Any link for the impedance calibration method?
IEC says to take a known transducer with a "constant volume displacement" and use it to drive the ear simulator. The transducer must have a very high acoustic impedance compared to the load, something very strongly stiffness dominated. You should be able to do this with a 1/4-inch pressure mic with a very high natural frequency as your speaker and use it to drive the coupler.
That suggestion was lifted from an old B&K note, "The Impedance of Real and Artificial Ears", p16. Probably still worth a read concerning earphone measurements.
 
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SIY

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Greetings to @SIY ! I hope you could guide us some tips for industry standard IEM measurement that doesn't cost a bomb.

Unfortunately, the industry standard measurement setups I've used are all pretty expensive ($10k and up). I'm surprised that someone hasn't built a lab grade system for IEMs (which takes out some of the complication) for $1k or so, but so far, if they have, I haven't seen it.
 
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Earfonia

Earfonia

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Unfortunately, the industry standard measurement setups I've used are all pretty expensive ($10k and up). I'm surprised that someone hasn't built a lab grade system for IEMs (which takes out some of the complication) for $1k or so, but so far, if they have, I haven't seen it.

Noted thanks! And what would be your cheapest recommendation?

How about Larson Davis Occluded Ear Simulator Model AEC304:
http://www.larsondavis.com/products/audiometercalibrationsystems/audiometercalibrationcouplers#Specs

Is it good enough? Thanks!
 
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SIY

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SIY

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You could rent a Larson Davis calibrator (I used a CAL250, it's 114dB but that should still work fine for you).
 
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Earfonia

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You could rent a Larson Davis calibrator (I used a CAL250, it's 114dB but that should still work fine for you).

For less critical application where super high accuracy measurement is not required, can we estimate coupler microphone SPL calibration using IEM factory specs like for example, specification of Etymotic ER2XR:

Sensitivity (@1 kHz) SPL at 0.1v : 96 dB

https://www.etymotic.com/er2-new.html

Can I calibrate my coupler mic SPL reading by the following steps:
I use REW:
1. Set playback tone: 1kHz.
2. Split the headphone output to ER2XR and True RMS voltmeter.
3. Set REW playback volume to ER2XR at exactly 100 mV / 0.1V measured at voltmeter.
4. Calibrate the SPL reading on REW SPL Meter to 96 dB SPL.

20200317_014314s.jpg 20200317_014022s.jpg

2020-03-17_IEC60318-4_TypeE610A_96dBS_1kHz_Desktop2.png


Is the definition of IEM sensitivity specification, is the SPL reading from standard measurement equipment like IEC 60318-4 coupler + calibrated microphone?

Thank you! Sorry many questions :)
 
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SIY

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Here's an easier way which is likely to be just as accurate: use the sensitivity rating that was supplied with the mike capsule. They're usually good to within a dB or so, and it's likely more trustworthy and repeatable than the SPL rating of an IEM.
 
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