Do you mean by measuring the voltage output from the microphone and do the math?
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.
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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
Pretty much, though your software might do the math for you.
If you have access to a calibrated handheld SPL meter, you might be able to take measurements of nearfield speakers with both that and your mic and calibrate to that...
I know that I'm little late on this. But firstly your choice is fine. It's a standard coupler and AP also endorses David Larson.
I would recommend ra0045 coupler or bk 4195. Aco japan also offers some cheaper alternatives. All complying to the standard.
On the standard, there's still only one iec711, aka, iec60318-4 standard, that's the old one. There's no other standard at this moment. Also the peak at 13.5k is desirable.
To see if you get the correct response just hook up a pair of er4s and compare to the manufacturer provided response which is measured on gras ra0045. Never ever use the newer hires/high frequency couplers. They suck. However this doesn't mean that the ra0045 is perfect. The couplers only actually works with deep inserting types like CIEMs and etymotics. You need to measure a lot of earphones to really get the intuition of the coupler. And what they are able to tell you. Some information you need experience to extract. On the other hand the new hires couplers remove the information altogether so that it always looks good which is plain wrong.
I don't want to spend too much time on this but you should get the idea.
Some Chinese couplers like rstech are pretty good too, I have one, measuring basically the same as ra0045. I have used ra0045 and 4195 as well as 4128c when I was visiting Moondrop in 2018.
http://www.rstech.com.cn/goods!changeLanguage.action?flag=en&pid=fbb92eaa57642edd015764775a30000cDo you mind to share link for the rstech Chinese couplers? Thanks!
http://www.rstech.com.cn/goods!changeLanguage.action?flag=en&pid=fbb92eaa57642edd015764775a30000c
Mine was not directly bought from them but a second hand.
I think the way they do it is looking at the resonance the coupler has. This shows up as a peak in the FR in the treble. Reviewers align that peak for every IEM they measure. (I think Crinacle and Super*reviews align @ 8kHz) This way they have some kind of standard to compare results.Can not understand the way all theese couplers supply stable insertion depth. Do they do it some way?
The thing is, own experiments force me think even small insertion depth difference results in very different peaks/dips on the FR plot.
In other words, can anybody get two equal FR with IEM reinsertion between them? Long hard practice?
Probably more handy to say about a system: coupler + (IEM with eartip). I guess, peaks/dips places/levels are defined by the system in a whole rather a coupler alone: different FR take place depending on insertion depth.resonance the coupler has
Yes, correct.Probably more handy to say about a system: coupler + (IEM with eartip). I guess, peaks/dips places/levels are defined by the system in a whole rather a coupler alone: different FR take place depending on insertion depth.