JaZZ
Headphoneus Supremus
No offense, but it seems your experience with IEMs is rather limited. Damping on both sides of the driver is an inherent part of (professional) IEM tuning. Actually, a large number of IEMs come with front side dampers already installed.
Besides, Rin Choi (who knows a lot more about this subject than any of us) has shown that a small amount of added acoustic resistance improves the IE800's treble in both smoothness and extension (see "ON SECOND THOUGHT #3"). Same goes for minor frontal leakage, which has been measured (on the FX700, iirc) to cause a reduction of bass levels, first and foremost in the sub-bass range.
Seems you guys are extrapolating from speakers or something like that. Anyway, as far as IEMs are concerned, you're barking up the wrong tree.
Last not least, please note the THIMC ("to whom it may concern") at the top of my post. You don't want to smooth the top or bottom? Fine! Feel free to ignore it.
Well, I must concede that I haven't opened any driver of the various IEMs I own to check what's inside. As far as damping on both sides is required, I just don't know, but am not going to believe this offhandedly. I can imagine that it's beneficial to have some damping in the canal reaching from the driver membrane(s) to the eardrum to suppress standing waves. But it's not a matter of inserting a thin damping fabric anywhere. An abrupt change of acoustic impedance inevitably causes an interference of transient and frequency response. That's no different in speakers and IEMs, which are mini-speakers. It may be beneficial if it's in the right place where it makes for a compensation of an existing irregularity, though. But that doesn't mean it's beneficial when you place it anywhere.
I do smooth both top and bottom of the IE 8's frequency response because it sounds better, more neutral to me, via equalizer. But feel free to do it your way!
[edit:] The provided link (which I had overlooked at first) was an interesting and informative read. It seems that I have to try the fabric mod and stand corrected in the case of the IE 800 insofar as the fabric insert is exactly at the right place where it's possible to insert it to compensate for an existing irregularity – by chance. I don't think I will make use of the bass compensation by the leaking effect, though, as it causes an unwanted loss of efficiency at low frequencies, while the bass response can be perfectly equalized with an equalizer – other than the treble response, if the linked graph is really universally valid for every pair of ears (which is usually not the case with the upper end of frequency response graphs).
Now the ER-4PT – which you may know – benefits enormously from replacing the green filter membrane with some slightly compressed loose wool fibres. It removes the treble harshness, apparently introduced by the filter membrane.
Or the SE846 with its swappable filters: it sounds best with all filters removed. It didn't sound good to me without any filter tube, but an empty tube created the ideal high-frequency characteristic. So I felt confirmed in my conviction that changes of acoustic impedances are to be avoided if possible or designed to be smooth, not abrupt. Except for cases where existing irregularities have to be compensated.
Why didn't you like the 120II with the IE800s?
