I note that the ER4PT comes with a certificate of sorts indicating the left and right channels are balanced to within a certain tolerance. The ER4S, however, does not come with this certificate. Does this mean the ER4PT are made to a closer tolerance than the ER4S? And if not, why don't Etymotic include such a certificate with the ER4S?
The reason I ask is that I bought a pair of ER4S late last year but the left driver sounded different to the right driver (the left emphasised frequencies in the 2 - 6 Khz range more than the right driver did). So I swapped the channels on my source WAV files using Sound Forge Pro, swapped the foam on each earpiece and then swapped the earpieces around in my ears (so as to eliminate the differences in my hearing ability in each ear). I also inserted new green filters in each earpiece to eliminate that as the cause of the problem. But the problem just moved with the errant driver to the other ear, meaning it was an Etymotic problem, not a human or other equipment problem.
So I have been wondering ever since whether the original pair I tried had a fault (strange considering they are hand made and thoroughly tested at the factory and they were brand new), or whether I am just incredibly sensitive to drivers which don't measure precisely, or whether even perhaps there was an issue with the cable (with it's inbuilt resistors).
Sort of makes me wonder whether I might be better off buying the ER4PT and terminating them myself with selected, better quality resistors. And in actual fact, if they balance the drivers to within 1.5 dB, that is actually quite audible in my opinion and experience, especially if it is in part of the frequency range to which were are the most sensitive (say 2 - 4 Khz). It was actually the emphasis of the tape hiss and vinyl surface noise that gave the difference away, but I even heard the difference with a fully digital 24/96 download too.
Edited by ADD - 2/22/13 at 6:53am