EtyDave エティ
http://www.head-fi.org/forums/posts/by_user/id/450423
http://www.head-fi.org/t/538615/if-you-still-love-etymotic-er4-this-is-the-thread-for-you/7380#post_12521183
http://cdn.head-fi.org/f/f9/f9f5c600_ER4SRvsER4XR1stLotComparison6.08.16.jpeg
That's different in the new models.
The new ER4SR and ER4XR are both 45 ohm earphones (and have the same 1khz sensitivity).
They no longer share the same driver.
The new ER4SR driver is *slightly* different than the old one (I'm not going to oversell that),
but it hits our target curve a bit more closely and is about 6dB more sensitive than the old model, which we think is nice.
The new ER4XR has basically the same response as the ER4SR except for an intentional lift in the low frequencies.
While the ER4P tilted the response which gave the impression of a warmer earphone with a bit more bass,
the new one is basically flat in the mids and the highs but has a bit of a boost in the low end.
Because the drivers are different, there is no longer the possibility of a converter cable.