got a little free time this morning so I went on with it. here are my cheap amateur measurement rigs in a few examples (not enough to really get a pattern, just enough to make a mess ^_^).
gear used:
-output: Odac/O2
- IEMs: ER4SR(sealed deep insertion), XBA_C10(sealed, can't go deep), Fiio EX1 AKA rebranded Titan1(super mega vented and dynamic driver).
-inputs: that's where it gets fun.
option 1@@@@: MiniDSP EARS (USB)
option 2@@@@: IMM6 made to use on cellphones and tablets.
I fed mine with a cellphone for the DC voltage, but recorded into a Scarlett 2i2.TBH as far as FR is concerned, I get almost the same results with a cheap 30$ Startech USB ADC, or even with my laptop's mic input.
a silicone tube is added to be able to measure IEMs with a seal while at a more appropriate distance(see the hundred measurements done by
@crinacle using this little cheap mic).
option 3 @@@@: EMC8000 stuck into a fake IEC711 coupler, massively DIY as the 2 didn't fit by default. (XLR, needs 48v phantom power).
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I have the coupler on the right
option 4@@@@: Vibro Veritas v1. plugged into a 30$ startech USB ADC/DAC.
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the color code follows the measurement rigs in the graphs for pretend clarity^_^. so green is always something measured with the IMM6.
I used the same source and output level for each group of measurements, first set the IEM to output 90dB SPL@1khz, then calibrate each rigs so REW would read 90dB@1khz. I also tried my best to get the resonance spikes around the same frequency when it was physically possible. no calibration, compensation or smoothing was applied. the EARS comes with a DF compensation but it would make no sense to use it for that comparison against RAWs.
Etymotic ER4SR into various rigs:
Sony XBA_c10:
Fiio EX1 (old one):
to my ears, the EX1 has a lot more subs than the ER4SR or the XBA_c10. I hear the ER4SR with an attenuated low end(I EQ it with a +6dB boost in the subs stating around 100hz). the XBA_c10 feels really close to my idea of flat. and the EX1 has the very sort of boosted low end that I adore. so while the quantities are clearly wrong, my Frankenstein rig with the EMC8000+coupler is the only one to follow the general direction of what I'm hearing. the others IMO always show too much subs on sealed stuff and not enough on vented IEMs. and while I can compensate the EMC8000+coupler to push all the low end up by some value and stick closer to perceived response, it's not something I can really control on the other rigs. the only choice would be to have a sealed calibration and a vented calibration. else the results between IEMs really don't follow subjective impressions. so that's something to check for people trying to set up their little amateur system.
all in all, for frequency response graphs only, I'd suggest to stick to the IMM6 and some app. it's cheap, small, practical, and with a little testing done on silicone tubes of various lengths, we can really work out something with most of the resonances close to how they are on graphs from expensive dummy heads. the EARS has the very obvious advantage to make for easy measurements of headphones without making our own "dummy box" for the head. but I'll wait to see if I can solve my issues before advising to buy one(if you get it for IEM measurements, prepare the tweezers to go fishing for tips).
for distortions and stuff like that, there are plenty of microphones with lower noise floor and better overall fidelity than an IMM6. but if cheap stuff could do it all with great results, there would be no need for people to invest in the kind of rig
@jude has for HeadFi. at some point, we always have to face reality. pro gears have different requirements and costs. but to have some fun and learn a great deal through experimentation, any cheap solution has something to offer IMO.