I am on a quest. I listen to music on the go. A lot. Usually on an iPod; either a shuffle or a 30 gig. And when I'm on the go, I want to use in-ear headphones. Not the disc-shaped ear buds -- things I stick into my ear for a snug fit.

I want in-ear headphones because they seal out some ambient noise. Sealing out ambient noise means that I can hear the music better, but it also means that I won't have to play music as loud as I would with open headphones. Yes, this is another headphone rant.

On this quest, I've tried a lot of headphones. Here is the rundown.

Apple iPod Ear Buds

Overall, not too bad. A lot like Bose speakers, these ear buds are carefully tuned to feel punchy when listening to pop music. Punchy often doesn't mean accurate, but Apple tried to make them sound pleasing. Downsides? Don't bother listen to strings with these headphones. They are OK for LCD Soundsystem, or something like that. To sound good, they need to be snug in your ear, but they tend to wiggle loose. Additionally, the little foam covers that help keep the ear buds in your ear tend to fall off the headphones rather easily.

Apple In-Ear Headphones

Wow. Very disappointing. I expected these to sound much better than they do. Seriously lacking in bass and harsh upper-mids. I really didn't like these.

Sony Fontopia (MDR-EX71SL)

This was the first set of replacement headphones I bought, and I seem to have been really lucky. The first pair sounded really pleasing. Deep, abundant (if not a little overemphasized) bass, good mids, but somewhat attenuated upper frequencies. I remember how well they handled Radiohead's The Bends. Good stuff. The also sealed the ear fairly well. I used these Sony headphones for months, finally wearing them out. Each replacement set I bought sounded terrible. Harsh highs, little bass. I bought three replacement sets; all three were equally bad. I'm not sure if the first pair was a fluke, or if I somehow managed to purchase three sets of defective headphones. Very strange.

Future Sonics EM3

These are interesting because they are built around a foam earplug-like material, so they block out a great deal of ambient noise. Sonically they are pretty good, but you can tell their heritage is that of a stage monitor. Mid tones are emphasized at the expense of the far ends of high and low frequencies. Still, they have a relatively even, pleasing sound, particularly good for rock. Nice with Led Zeppelin III. Vocals and electric guitars sound particularly good. The only thing really lacking is the kick of very low bass. Also, quite a comfortable in-ear headphone.

Shure E5 isolating earphones

These have an interesting sound. I didn't find them as pleasing as others I've used, but I can see why people like them. Very rock-sounding earphones. They feel uneven to me; I didn't enjoy listening to them. This may be a little unfair, because these are rather high impedance headphones. I'm not sure if an iPod can really drive them. The headphones are also less comfortable (to me) than others. The pads were rather hard, didn't hold well in my ears, shaking loose too often.

Etymotic ER-4P MicroPro

These should be the best in-ear headphones I have, probably by a large margin. I really want to like them more than I do. They are terribly expensive (for ear bud headphones), and Etymotic markets them with such gusto. And they come in this snappy case with ten sets of "ear tips," extra "filters," a "filter changing tool," a headphone carrying case, and an instruction booklet. You can't beat that with a stick.

First the bad, so I can dwell on the good: bass, dammit. These headphones seem to drop off between 60 and 150 Hz. This is particularly frustrating, as they are really, really flat above that range, and very clear, reproducing the subtlety of a recording terribly well.

If I only listened to string quartets or orchestral music, I'd love these headphones. It is particularly nice to listen to a well recorded string piece and to feel the texture of the bow on the strings. Or to feel the clear separation of the microphones on the piano in Joni Mitchell's My Old Man. If anything, these headphones are notable for their excellent separation between tones. They really preserve a stereo image well, and are a pleasure to listen to. I just miss the lowest tones that I know are present, attenuated by about 5 dB. To get the best sound, though, these headphones have to really be jammed into your ear. Unnaturally so, like you wanted to stab your brain. A nice side effect of this is the isolation; you can't hear a thing with them in your ears.

Lest you think I'm some bitchy kook who won't be satisfied with any headphones, I can't say enough about the quality of the Sennheiser 590s I use when I'm stationary.

Listening to a recording through these headphones really is exciting. You hear unexpected details and subtlety. Fingers dragging across frets; pads closing on a saxophone; Eliot Fisk breathing as he works through some Scarlatti. Closing your eyes and listening to a good recording really is a pleasure with these headphones, because the sound is so good, so clear, and so even that you have an experience better than being there. These headphones put you in the middle of a performance in a remarkable way.

I so clearly remember the big moments in my music listening past. Each time I heard music through a better system, it was like hearing the music for the first time. From 33rpm vinyl a bad needle and junky speakers, to a cassette tape with better speakers; a CD through better speakers; a Marantz SA-CD player through McIntosh speakers. Each time the differences are subtle, but audible and important. You think, "yes -- this is how it should sound." Each time the music is new, better, and you discover little surprising things. This is the difference between junky headphones and the Sennheisers.

There is no "best" music for the 590s. Everything sounds wonderful.

And the bass; ah, the bass. You feel the punch of DMX's Keep Your Shit the Hardest deep in your brain, the kick drum in Metallica's Enter Sandman is like an hammer hitting an anvil. These headphones are remarkable for the range of tones they reproduce, the clear separation of tones, and the flat, even response while doing it. I'm tempted to get a set of HD 650s just to see if they can possibly be better.

So I'm still looking. Always open to suggestions.