I've been playing around with measurement of In-Ear monitor Impedance Curve using REW Impedance measurement feature.
Many thanks to @JohnPM for the great software!
So here I just simply want to share my setup and things that I've learnt so far.
The setup:
Audio Interface: RME Babyface Pro
Output: Analog 3/4 - 3.5mm Headphone Output (2 ohm output impedance) volume set at -6 dBFS.
Input: Analog 3/4 - 1/4" TS (1 Mohm input impedance) input mode set to -10 dBV, gain set at 9 dB (Max). Fader muted to avoid feedback.
DIY cable following the diagram from REW website:
https://www.roomeqwizard.com/help/help_en-GB/html/impedancemeasurement.html
Rsense: 75 ohms
Measurement Level:
For testing I found measurement level around -30 dBFS to be optimum for IEMs.
Less than -40 dBFS raises 'low level' warning on REW.
Around -20 dBFS sometime causes clipping around the peak area on some IEMs.
Then sweep level adjusted per driver to get around -30 dBFS measurement level.
I found that between -20 dBFS to -40 dBFS when there is no clipping, measurement results is very2 close, therefore it is not significant to accurately match the measurement level between drivers / IEMs.
I also tried measuring the IEM when it is worn in my ears (sealed) compared to just put them on the desk (not sealed), and there is no significant different in the result as well. So for impedance curve measurement, I left the drivers open, not sealed in the ear canal (not comfortable to hear that loud sweep again and again).
Here are some impedance curves from 7 IEMs I measured today:
The light grey line in the middle is setup calibration with 32 ohm resistor.
Here is the REW file if you want to check it for yourself, and you can observe the phase curve as well when viewing the individual curve.
https://drive.google.com/file/d/1idlv0ZbOA4EASztS_rXNbDoIAS-HZTZr/view?usp=sharing
If you see error in the measurement setup or anything that can be improved, please let me know. Thanks in advance!
I'm revamping my review process and content for IEM and will include impedance curve measurement in it. Any suggestion is welcome!
Many thanks to @JohnPM for the great software!
So here I just simply want to share my setup and things that I've learnt so far.
The setup:
Audio Interface: RME Babyface Pro
Output: Analog 3/4 - 3.5mm Headphone Output (2 ohm output impedance) volume set at -6 dBFS.
Input: Analog 3/4 - 1/4" TS (1 Mohm input impedance) input mode set to -10 dBV, gain set at 9 dB (Max). Fader muted to avoid feedback.
DIY cable following the diagram from REW website:
https://www.roomeqwizard.com/help/help_en-GB/html/impedancemeasurement.html
Rsense: 75 ohms
Measurement Level:
For testing I found measurement level around -30 dBFS to be optimum for IEMs.
Less than -40 dBFS raises 'low level' warning on REW.
Around -20 dBFS sometime causes clipping around the peak area on some IEMs.
Then sweep level adjusted per driver to get around -30 dBFS measurement level.
I found that between -20 dBFS to -40 dBFS when there is no clipping, measurement results is very2 close, therefore it is not significant to accurately match the measurement level between drivers / IEMs.
I also tried measuring the IEM when it is worn in my ears (sealed) compared to just put them on the desk (not sealed), and there is no significant different in the result as well. So for impedance curve measurement, I left the drivers open, not sealed in the ear canal (not comfortable to hear that loud sweep again and again).
Here are some impedance curves from 7 IEMs I measured today:
The light grey line in the middle is setup calibration with 32 ohm resistor.
Here is the REW file if you want to check it for yourself, and you can observe the phase curve as well when viewing the individual curve.
https://drive.google.com/file/d/1idlv0ZbOA4EASztS_rXNbDoIAS-HZTZr/view?usp=sharing
If you see error in the measurement setup or anything that can be improved, please let me know. Thanks in advance!
I'm revamping my review process and content for IEM and will include impedance curve measurement in it. Any suggestion is welcome!
