He doesn't know.
There is just as high a likelihood that FitEar are using the Sonion 2389, but this is a moot point. The 2389 is Sonion's analogue to Knowles' ED-29689; they share the same overall design principles, armature shape, back volume, etc. Measured bare, without any additional modification, they perform remarkably similar to each other. Neither is better.
The real engineering behind the F111 is the titanium acoustic horn. It's designed to boost mid-to-high frequencies without the need for electrical underdamping of the driver. Even Mead Killion, founder of Etymotic, stresses the importance of a good, robust acoustic horn design for the maximum potential of a sound system, whether it be a hearing aid or insert earphone.
So yes, the F111 is almost twice the price of the ER4S, but there's a reason why. Precise machining of titanium costs money, and so does hand-made construction. The ER4S uses neither. This is not an attack on the ER4S; it is an excellent IEM, and is still one of the best in the world.
So the F111 doesn't underdamp the driver electrically, while ER4 does. Is that right? What is the advantage of not electrically underdamping the driver? Can you explain this a little more? You seem to know quite a bit about this stuff.
Also, are there any detailed measurements for the F111? From what I've read so far, it seems that the F111 is a very similar design to the ER4 with a very similar frequency response. Ok, but how about impulse response, CSD graph, square wave response, distortion levels and other measurements that tell us more about the actual sound quality? How can one possibly be sure that the F111 is any better than the ER4 at all without these objective measurements? Why would anyone serious about sound quality want to just blindly shell out all the extra money for something that, based on the information I've read so far (ok, maybe I missed something), is perhaps nothing more than just a different version of the ER4 with a somewhat different sound? It amazes me that people are completely ignoring the fact that it is a single armature with nearly identical response to the ER4, somehow still expecting it to sound better. Jeez. And if you think that you can just trust your own ears, have you forgotten about placebo and how powerful it can be?
One question, though: Is it not possible to hear the bass and (somehow) also feel it? Are these two aspects mutually exclusive? I ask because the main reason I sold my F111 was precisely because of its rendering of low frequencies, which ultimately was not always fully convincing, at least not with quite a few albums. As I said before (elsewhere, I think), I kept reaching for my FI-BA-SS much more often, and the latter is by no means a bass-head's IEM.
How can you feel bass with headphones? It's impossible, unless you mean the physical vibrations of the headphones on your head, or IEMs in your ear canal. lol
Edited by Pianist - 5/22/13 at 7:09pm