This got me thinking, perhaps the distortion may also be a result of not just the driver type, but the pad type, as almost all those dynamic headphones I listed have velour pads, while most planar magnetic headphones have leather/pleather pads that seal better. That's just a guess, however, I still don't understand why there is significantly more 2nd order harmonic distortion in the bass on many of these dynamic drivers.
Does this type of distortion really detract that much from perceived sound quality, and is it reason to go with a different driver type such as planar magnetic or electrostat?
I know both planar and electrostat headphones are described as being "faster" and cleaner, but is that due to frequency response mostly or does this distortion actually affect the bass that significantly?
Edit: also, I have the Klipsch X10, which is a BA driver IEM, and I can hear audible distortion in the 1 Khz area, even though graphs on innerfidelity show the distortion levels to be consistently under 1% at that frequency. I'm not sure if what I am hearing is actually harmonic distortion, but it doesn't sound like a pure tone at 1 Khz.
I'm not so sure harmonic distortion in balanced armature IEM's is inaudible, at least on sine waves.This measurement of the ER4SR shows ~0.5% THD at 1kHz, and it's almost all 3rd harmonic:http://clarityfidelity.blogspot.ca/2016/09/etymotic-research-er4sr-iem.html(That doesn't seem unusual, looking at other BA IEM's on Speakerphone and Rin Choi's blog)Here is an experiment I tried: In Audacity, generate a 1kHz sine wave, then a 3kHz sine wave in a separate track. Select the 3kHz track and amplify it by -46dB (attenuation factor for 0.5% THD according to this calculator: http://www.sengpielaudio.com/calculator-thd.htm ). Now play the two tracks together, and mute/unmute the 3kHz track. Spoiler: the -46dB 3kHz tone should be very easy to hear, even at low volume levels.Did I mess up anything, or should that simulate the ER4SR's distortion when playing back a 1kHz tone?Blind testing with a music sample would be more interesting... anyone know of a tool that can apply distortion to a music sample, according to a 2nd/3rd/4th/etc. harmonic distortion % vs. frequency graph?