Can anyone with the ER4S and high quality amplification, source and DAC (and obviously acute listening skills) do me a favour and download the attached 10MB file please (low_level_grunge_ER4S.zip)? It contains two short classical extracts I have created for listening with the ER4S. They highlight an issue that I have been noticing and it is annoying me quite a lot. What I seem to be noticing is that at low listening levels to classical music, I am hearing a sort of resonance or "fuzziness" that seems to come directly from the barrel of the ER4S earphone and is not a component of the music itself. But if I turn the volume up to a level louder than I normally listen, the problem is no longer evident. That is why I would describe it as some sort of innate resonance - a bit like how the exhaust on a car can resonate at particular engine revolutions and throttle openings.
The two extracts in low_level_grunge_ER4S.zip are very quiet classical passages, so you can listen to them at their normal low level or turn them up to a higher level than you would normally listen and it still won't be loud. This then highlights what I am noticing - there is a strange resonance, grunginess or fuzziness - whatever you want to call it at low levels which disappears if you turn the volume up. There is specific volume setting I use that makes the problem really bad but then increase or decrease the volume and it is much less or non-existent - again this would seem to be consistent with some sort of resonance in the units themselves.
Now these extracts have been processed with Dolby Headphone and equalised to accord for the both the spectral artifacts from Dolby Headphone as well as the ER4S itself. But before you switch off and refuse to listen, the reason I have done this is because the Dolby Headphone will place the musical content 15 feet in front of you, but any sounds coming from within the earphone itself will obviously be coming from your ear canal - at least as perceived by your brain's auditory system. The problem is more easily hidden without Dolby Headphone because the musical content and any strange sound from the earphone itself are - to your brain - coming from exactly the same place - so there is this masking effect.
In order to be sure it wasn't something strange with my hearing, I reversed the channels in these extracts then reversed the earphones as well - so that I was hearing the left channel of the music via the right earphone in my left ear. This time the resonance was not as bad, though still audible. This suggests to me there is a manufacturing inconsistency between individual units (as opposed to paired sets), since the only variable in this experiment was which earpiece I was using (I also tried swapping the green filter and tip but this made no difference).
In listening to these extracts, you should notice the problem worse in the left channel than right, mainly as the problem seems to effect treble stringed and woodwind instruments more than other instruments.
I have also uploaded a second file - this is nothing more than a 60 second sine wave at 440 hz and -25dBFS. When I play this through the ER4S, I hear a very odd artifact - sort of like intermodulation distortion. But I do not hear this problem through any other headphone I have ever tried - I just hear the pure 440 Hz tone. And again, as with the music extracts, changing the volume changes the degree to which this strange artifact impedes on the test tone itself - this again suggests some sort of resonance issue with the ER4S.
All files are 24 bit, 48 Khz sample rate.