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After some discussion with fellow headfi measurement enthusiasts, I thought it would be helpful to send a pair of Etymotic ER2SE dynamic driver IEMs out on a world tour. The aim isn't to produce a set of reviews for these headphones (and I'm not going to give them marks out of 5 here), but rather to provide a reference data point for our mics and couplers so that we can come to some common agreement. Several of us have 711-compliant couplers which still may have their own small unit variations. Others are using tube couplers that might benefit from a calibration file derived from a common reference measurement (at least for a sealed/non-ported IEM).
Here's my logic in choosing the ER2SE with stock small silicone (frost) flange tips as a reference:
1) They should easily fit and seal well in any coupler.
2) The stock silicone triple flange tips will hold the IEM in place reasonably well even without the additional use of mounting putty (though putty is still a good idea because it stops any vibration of the IEM in the coupler).
3) There can be no ambiguities from variations in preparing or rolling foam tips. (Ok, eartip effects turned out to be more subtle than I thought... More on this later...!)
4) They're relatively neutral, with no wild FR swings.
5) They have very low distortion, which makes for an interesting challenge in trying to compare THD measurements.
6) They have a flat impedance curve, so no wild swings in FR, even if higher z-out sources are used to drive them.
7) We got them at a reasonable price, many thanks to @wquiles
I suggest using the stock small-sized (frost) triple flange tips, at least as a starting point. If you use the larger-size tri-flange tips, you'll see a definite change in your measurements. It should be possible to find an insertion depth where the resonance peak sits at (or similar to) those shown in the figures below (see also first spoiler link for a photo). Ideally, to get the best agreement, you'd want to try and match the primary resonance peak that I ended up with (~10.5 kHz). Also, note that the left channel is unit number 002527; the right is unit number 002528. The ER2SE uses MMXC connectors, so be careful here, because the left and right buds CAN be swapped over. The only way of knowing consistently which is which is by those serial numbers printed on the IEM body.
SPLs at 200 mV, 1 kHz sine wave (N.B. This may be coupler-dependent):
Left channel (SN 002527): 104.4 dB
Right channel (SN 002528): 104.3 dB
SPLs at 200 mV, 500 Hz sine wave (Hopefully this is less coupler-dependent):
Left channel (SN 002527): 102.2 dB
Right channel (SN 002528): 102.0 dB
Following some useful input from @yuriv, the suggestion is for us all to try and measure frequency response using a volume level set to 94 dB for a 500 Hz sine wave. (Some variation around this SPL won't matter much for these IEMs.) For THD measurements, I've used 80 dB @ 500 Hz and 94 dB @ 500 Hz. Feel free to use something else for THD if you prefer, but please report what SPL you used, and please be careful and don't fry our headphones!
Unfortunately, somewhere along the tour it looks like somebody's dog ate the packaging. This is what it used to look like:
A sample set of initial results are given below to get us started. (If anybody would like any of this raw data in ASCII or REW/mdat format, please pm me.)
If anybody would like to join this tour, please jump on the bottom of this thread with a request to the last person with the headphones (they're currently with @yuriv and the plan is, I think, for them then to go to @hakuzen, then @castleofargh). I'm not worried about the financial loss if they go missing, but bear in mind they're basically irreplaceable, because no other set of ER2SE is going to measure exactly the same. So I'm trusting you folks to package them carefully and post them on with a reputable shipping company!
Have fun and let's all (hopefully!) learn something
Here's my logic in choosing the ER2SE with stock small silicone (frost) flange tips as a reference:
1) They should easily fit and seal well in any coupler.
2) The stock silicone triple flange tips will hold the IEM in place reasonably well even without the additional use of mounting putty (though putty is still a good idea because it stops any vibration of the IEM in the coupler).
3) There can be no ambiguities from variations in preparing or rolling foam tips. (Ok, eartip effects turned out to be more subtle than I thought... More on this later...!)
4) They're relatively neutral, with no wild FR swings.
5) They have very low distortion, which makes for an interesting challenge in trying to compare THD measurements.
6) They have a flat impedance curve, so no wild swings in FR, even if higher z-out sources are used to drive them.
7) We got them at a reasonable price, many thanks to @wquiles
I suggest using the stock small-sized (frost) triple flange tips, at least as a starting point. If you use the larger-size tri-flange tips, you'll see a definite change in your measurements. It should be possible to find an insertion depth where the resonance peak sits at (or similar to) those shown in the figures below (see also first spoiler link for a photo). Ideally, to get the best agreement, you'd want to try and match the primary resonance peak that I ended up with (~10.5 kHz). Also, note that the left channel is unit number 002527; the right is unit number 002528. The ER2SE uses MMXC connectors, so be careful here, because the left and right buds CAN be swapped over. The only way of knowing consistently which is which is by those serial numbers printed on the IEM body.
SPLs at 200 mV, 1 kHz sine wave (N.B. This may be coupler-dependent):
Left channel (SN 002527): 104.4 dB
Right channel (SN 002528): 104.3 dB
SPLs at 200 mV, 500 Hz sine wave (Hopefully this is less coupler-dependent):
Left channel (SN 002527): 102.2 dB
Right channel (SN 002528): 102.0 dB
Following some useful input from @yuriv, the suggestion is for us all to try and measure frequency response using a volume level set to 94 dB for a 500 Hz sine wave. (Some variation around this SPL won't matter much for these IEMs.) For THD measurements, I've used 80 dB @ 500 Hz and 94 dB @ 500 Hz. Feel free to use something else for THD if you prefer, but please report what SPL you used, and please be careful and don't fry our headphones!
Unfortunately, somewhere along the tour it looks like somebody's dog ate the packaging. This is what it used to look like:
A sample set of initial results are given below to get us started. (If anybody would like any of this raw data in ASCII or REW/mdat format, please pm me.)
This is roughly the insertion depth you're looking for (ER4XR shown below, but the body housing is identical to that of the ER2SE):
In my couplers, these Etymotic triple flange tips finish pretty much level with the lip of the coupler opening for an ~10.4 kHz primary resonance peak. (N.B. If you push the IEMs in much farther than this, there's a risk of the eartip touching the grill in front of the coupler mic. This is something I noticed after having made my initial measurements and this is why I've now dropped that primary resonance peak from ~11.5 khz to ~10.5 kHz, i.e., a shallower insertion.) The mounting putty stops the IEM vibrating during measurements (which can show up as glitches in the FR). The coupler here is resting on a sorbothane pad, but this isn't necessary for basic FR measurements. I was driving the ER2SE from a QP1R (0.15 Ohm z-out), but higher z-out sources shouldn't substantially change the results as the ER2SE impedance curve is flat (see below).
In my couplers, these Etymotic triple flange tips finish pretty much level with the lip of the coupler opening for an ~10.4 kHz primary resonance peak. (N.B. If you push the IEMs in much farther than this, there's a risk of the eartip touching the grill in front of the coupler mic. This is something I noticed after having made my initial measurements and this is why I've now dropped that primary resonance peak from ~11.5 khz to ~10.5 kHz, i.e., a shallower insertion.) The mounting putty stops the IEM vibrating during measurements (which can show up as glitches in the FR). The coupler here is resting on a sorbothane pad, but this isn't necessary for basic FR measurements. I was driving the ER2SE from a QP1R (0.15 Ohm z-out), but higher z-out sources shouldn't substantially change the results as the ER2SE impedance curve is flat (see below).
Measurements here were made at an SPL of 94 dB @ 500 Hz:
Additional measurements using Comply Ts100 foam and SpinFit Cp800 silicone tips can be found in the following post: https://www.head-fi.org/threads/general-iem-measurements-discussions.903455/#post-14869632
Additional measurements using Comply Ts100 foam and SpinFit Cp800 silicone tips can be found in the following post: https://www.head-fi.org/threads/general-iem-measurements-discussions.903455/#post-14869632
Impulse Response
The dynamic driver in the ER2SE has even lower total harmonic distortion than that in the ER2XR and much lower that that in the (more expensive) ER4 balanced-armature series of IEMs. All THD measurements here were made via stepped-sine sweeps at 80 dB:
Comparisons of percentage THD at 80 dB and 94 dB (both measured at 500 Hz):
Here are more detailed breakdowns of the distortion and noise components at 80 dB (@ 500 Hz):
and 94 dB (@ 500 Hz):
Comparisons of percentage THD at 80 dB and 94 dB (both measured at 500 Hz):
Here are more detailed breakdowns of the distortion and noise components at 80 dB (@ 500 Hz):
and 94 dB (@ 500 Hz):
Pretty much flat at 15 Ohm:
If anybody would like to join this tour, please jump on the bottom of this thread with a request to the last person with the headphones (they're currently with @yuriv and the plan is, I think, for them then to go to @hakuzen, then @castleofargh). I'm not worried about the financial loss if they go missing, but bear in mind they're basically irreplaceable, because no other set of ER2SE is going to measure exactly the same. So I'm trusting you folks to package them carefully and post them on with a reputable shipping company!
Have fun and let's all (hopefully!) learn something
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