Whenever New York's weather is not conducive to cycling, I clip an iPod and portable amplifier to my belt and enjoy 2-3 hours of music during my daily commute. I started off with a Porta Corda-I (PC-I) and Etymotic ER6, which were a huge improvement over the barefoot iPod and various Walkman-styled phones I had tried then discarded. Later, I bought ER4Ps but found them excruciatingly microphonic when walking; once seated in the train, however, I could appreciate that they had a much cleaner midrange than the ER6 and were generally more "dynamic" sounding.
Having tasted something better than the ER6 but finding the ER4P unsuitable during the major part of my commute, and figuring that passing the cables over my ears might reduce the microphonics, I treated myself to a pair of E5cs. That fixed the cable noise but I was not exactly bowled over by the sound. Compared with the Etys, the Shures seemed to have a saddle-shaped response: lots of bass and high treble but nothing much in between. On the plus side, the soundstage did gain in breadth and depth. In time, I grew used to them but I felt there was insufficient excitement to justify their premium sticker price. I also grew unhappy with their bloated bass whenever I listened to a piece that had received too much equalization in that part of the spectrum. (The bonus tracks on the CD release of Elton John's "Captain Fantastic" are hideous in that regard.) Even engaging the PC-I's crossfeed could not tame it. I started to drift back to the ER6.
When HeadRoom announced their Total BitHead (TBH) model, I immediately ordered one to see if I could improve on the already excellent sound out of my PowerBook G3. It did, but not by much -- Apple did a great job with that motherboard. The logical next step was to substitute the TBH for the PC-I in my mobile rig and that's where things got really interesting.
The synergy between the TBH and E5c is extraordinary. On good classical and jazz recordings, the improvement in the soundstage is enormous. The TBH/E5c combination adds layers of ambiance cues that were simply inaudible with the PC-I. I no longer need to engage the TBH "processor" except for the most egregious "ping pong stereo" recordings. This is just as well, since the processor's peculiar effect on treble balance is painfully obvious through the Shures. The TBH's iron-clad control of low bass reduces the E5c's bloat to manageable proportions, while the E5c's high treble "tizziness" is less noticeable. The only downside is background noise: the E5c's very high sensitivity makes the TBH noise floor just audible. By comparison, the PC-I is dead quiet.
On a recent long cross-country flight, I had nothing better to do than perform a few mix & match comparisons. I found that with the ER4P (even converted to ER4S with an adapter cable), the differences between the TBH and PC-I were much less apparent. After listening to either amplifier for a few minutes, the memory of the other faded completely. This applied across the musical spectrum. Compared with the E5c, the sound was much more localized around each ear, making crossfeed/processing necessary to get the sound out of my head. Both amps revealed the improvement the ER4 represents over the ER6, as noted earlier. With rock and pop music, the TBH/E5c magic is not so much of an advantage, due to the somewhat recessed midrange. On some recordings, where the production relies on studio effects rather than recording space ambiance, I found the "up-front" presentation of the ER4 to be preferable, even allowing for the relatively lean bass response. There is no trace of bloat with the Etys, with either amplifier.
A word about E5c fit: I much prefer the triple flange adapter over the hard sleeves and the foam. (I have not tried the new soft sleeves.) In order to avoid discomfort while still allowing an adequate seal, I had to cut off the smallest of the three flanges. It now looks a bit like the original ER6 sleeve, but with a longer "stalk". I could never get the foamies to stay put and the seal was ineffective. The hard sleeves were uncomfortable, did not seal very well, and sounded harsh. I suspect that they partially reflect sound rather than absorbing it like the foam and the softer plastic. I pass the cable over the top of my ears then in front of my neck, rather than behind as Shure recommends. This results in the first contact with clothing occurring further from the ears, which reduces the microphonics significantly. The cable material seems to dampen the noise very effectively. I drop the cable down inside the front of my shirt, exiting between the buttons near my waistline where the amp sits attached to my belt in a HeadRoom MiniDisc bag. The iPod is attached next to it in a Waterfield Designs iPod case. It's about as secure and discreet as mobile sound gets.
