We're gonna be talking in-ear earbuds—canalphones, really, or in-ear monitors, if you're snooty—since all the good stuff goes deep into your precious earholes. We aren't talking about headphones because great headphones aren't the most discreet things around—can't defeat physics, children. Unless you derive some sick pleasure from jogging with a pair of giant cans bolted to your head, earbuds are the way to go.

It's All About the Drivers—No, Not Those Kind

Whether you're talking about headphones or earbuds, they work a lot like loudspeakers, just miniaturized. The key element in both are drivers, though earphone drivers are a lot smaller, and do a lot less work to make the same music.

There are two main types of drivers: The a dynamic driver works just like a traditional one in big ol' speaker. The benefit of the dynamic driver is that it produces a nice bass response, though it can be hard to miniaturize.

A balanced armature driver is pretty common in serious in-ear monitors, since it's easy to shrink down. Originally found in hearing aids, it houses a magnetic armature that moves when an electric current runs through the coil, putting pressure on the diaphragm, creating sound. It can be, and often is, paired with a dynamic driver.

Most earbuds just have the one driver, though more and more have multiple drivers. That costs more 'cause it's harder to cram more than one into a tiny casing meant to rest gravity-free in your ear. With multiple drivers also comes a "crossover network," circuitry meant to divide music into different frequencies and route them to the appropriate drivers, an additional payload to stuff into that tight space. Once all that is crammed in, however, multi-driver earbuds typically sound better than single-driver ones, because the woofer, tweeter and mid-range horn are more innately equipped to handle their own domains of sound—from boomy bass to sizzly treble.

Among the least expensive multiple-driver earbuds are Apple's fancier $80 in-ear earbuds, which use two drivers, a tweeter for highs, and another for everything else. It gets more expensive as you creep up. Shure's three-driver SE530 lists for $500 (but can be found for much less). Ultimate Ears' UE-11 Pro, which will run you a ridiculous $1150, come with a correspondingly ridiculous four drivers. That's one for mid-range and one for highs and two for bass.

Some companies opt for a single driver because they think it's better, since there aren't complications with crossover networks, trying to get all the drivers to work together to produce seamless sound. On the other hand, with a single driver, you're asking one driver to do everything: highs, lows and mid-range, says Stereophile senior contributing editor Michael Fremer Fremer. (Yes, that Michael Fremer.) That's why , FutureSonics, for instance, makers of pro monitoring gear, charges so much for their single-driver earbuds. "A really good single-driver can sound really good," says Fremer.

What It's Made Of, How It's Made

Besides more drivers, what you get in pricier earbuds is (surprise, surprise) better materials, finer build quality and a more focused design. Michael Johns, headphones manager for Shure—known for earbuds with MSRP ranging from $100 to $500 but rarely double digits—told me that most of the really cheap ($20) headphones on the market are basically rebranded crap from no-name factories, and that when you buy those with suggested retail pricing between $50 and $100, you're mostly paying for style, not sound. The top-tier brands, of which there are many, tend to design and engineer their own headphones. The expense of that is, unfortunately, passed on to you.

The cost of raw ingredients is also passed to you—the cable material, the magnet behind the diaphragm, the diaphragm material itself, the overall quality of the driver, and the enclosure. (Again, all of the stuff that jacks up the price of higher quality loudspeakers too.) None of that stuff, when it's well made, is cheap. Fremer says, for instance, that better headphones actually use stronger magnets than cheaper headphones. As you might guess, the more powerful the magnet, the higher the cost.

The Fit

With legit in-ear buds, fit matters a lot, because the seal is critical. Not only does a good seal mean less ambient noise infiltrates your ears—allowing you to keep your volume low while still catching the full dynamic range—but an airtight seal is how you get decent bass response. And you want something shoved deep down inside your ear to be comfortable, as well as fit, so there's a lot of different kinds of tips earbud makers have come up with. Besides the standard rubber bulb, there's squishy foam, and the Christmas tree-lookin' triple-flange sleeves. What works best often comes down to your own ears and personal preference, which is why better earbuds come with a ton of tips.

What Do I Buy?

So, uh, what's the sweet spot price for great headphones? If Shure and Fremer had their way, everybody would spend upwards of $200 on their earbuds, but if you twist their arm, they'll agree that $100 is where buds start getting decent. The real trick, according to Fremer, is just getting people to "spend that first hundred bucks."

The law of diminishing returns tends to kick in above that point: The difference between $300 set of buds and a $400 pair is nowhere near the jump from $20 to $100. Even smaller is the difference in models between generations. The best value on the market might be a previous-gen version of Shure's 500 series buds at a cut rate ($290), but if you can find $100 earbuds for 70 bucks, it's even better.

Interestingly, Fremer says what you're looking for in great earbuds is "a relatively flat frequency response so no frequency is accentuated above another," so "the product that sounds the best is usually the one that impresses you the least at first." Buds that tout big bass, for instance, don't actually have better bass, just more of it. (You can always adjust the EQ if you want more bass.)

Whatever you do, for Christ's sake—and yours—ditch the iPod earbuds.

Still something you wanna know? Send questions about buds, tips or hot waitresses who deserve big tips to tips@gizmodo.com, with "Giz Explains" in the subject line.

Koss is a pretty reliable manufacturer of low-cost eargear, so it's a little surprising to see them challenging the big boys with earbuds that clock in at $150, but perfectly adjustable fit is a great idea. Let's hope the sound quality warrants the price. The Koss CC_01 will be available this March. [DVICE]

First, some ground rules on the scope and purpose of my testing:

The headphones tested are all what you'd consider "upgrades" rather than "replacements" for the crap headphones that came with your MP3 player. While I capped pricing at $200, my "cheapest" pair started at around $40. The three tiers are under $100, $100-$150, and $150-$200.

The most practical measure of sound quality is to just sit and listen. I focused on in-ear headphones because they are built not just to jam a driver right next to your ear, but to block outside noise. It's simple: less ambient noise = better experience.

In the spirit of cutting out the vaguely scientific marketing jargon, my tests were unscientific, but consistent across the board and based on real-world situations. The methodology was simple: a current-gen iPod, a sonically diverse playlist of music and, for isolation testing, a seat on the 14 bus in San Francisco, then some time next to a white noise machine.

With so much of the earphone inside of your ear, rustling of the cable can cause some serious noise. If the cable isn't properly buffered from the earphone, the deep, annoying shuffling can interfere your music when you try to walk or turn your head. That's why I made note of "cable noise"—this isn't to suggest there was some kind of buzz or white noise from the cable itself.

The Losers: This is a tricky price point, as some stock earbuds (Apple, Sony) are actually pretty good. Slapping a rubber cuff on a half-baked product doesn't justify a price of $50+. In the case of Apple's in-ears and the CX300s, you aren't really experiencing a different class of audio than with stock buds, though there is a marked improvement. The CX500s put on a good show for bass junkies, but that's about it. Creative has a nice product with a great price, but it just can't measure up to the metro.fi on the performance front.

$100-$150
The Winner: Shure SE110 This price point offers the highest price to performance ratio, and the SE110 is the best of the lot. If you can get over the deep penetration and the over-ear looping, you'll find that the SE110s are comfortable, block out plenty of ambient noise and most importantly produce stunning, immersive sound. The tones are wisely balanced, and quality is at the level that you'll be noticing new things about songs that you've heard dozens of times. Decent discounts are available at various online retailers, as is the case with most of this category.

The Losers: Manufacturers know that this is a sweet spot for consumers, so the market is crowded with good options. The hardware starts to look a little more "professional," or more accurately, "weird." Etymotics, always fans of producing earphones that are really good on paper, fails with the ER6 not because of quality issues, but because the buds are awkward and overwhelm with the high and middle tones. The company's new earphone tips, however, are amazing (more on this below, in the more expensive category). Ultimate Ears loses their luster at this level. Creative is yet again a nice runner-up; the Zen Aurvanas are very capable, but couldn't supplant the crystal-clear SE110s.

$150-$200
The Winner: Etymotics hf5 Ostensibly designed with portable music players in mind, the hf5s solve the balance problems of the er6 models and much, much more. They're cool looking (with the right tips, they look like sci-fi laser pistols), have little to no cable movement noise and reproduce sound in a way that is both perfectly clear and highly enjoyable. Everything about these gives the impression of quality, from the brushed aluminum finish to the way that music suddenly sounds distinctly layered in a way that it didn't before, and that it doesn't on many similarly priced units. One caveat, though: the hf5s (and the er6s, for that matter) must be used with the new foam rubber tips, called "Mushrooms." They're a little phallic and sort of a sickly gray, but they are leaps and bounds better than Etymotics' trademark flanged tips. The tighter seal that these offer to most people is conducive to better listening, and the isolation properties are superb. You can't hear anything else with these guys in. Every manufacturer should have something like this. According to the Etymotics people, by the time the hf5s ship these will be standard issue. Good.

The Losers: To sum up the category: Expensive without enough added benefit. Spending $100 will get you a phenomenal listening experience, so it's hard to justify spending more. The $200 cap was intended to filter out the luxury market/audiophile products that tend to show up at about that price, but hints of both are apparent here. The Shure SE210s are a wonderful pair of earphones, but the large premium over the SE110s is a dealbreaker, as side-by-side comparisons expose only the slightest variation in sound quality. The Klipsch Custom-2s are more of a luxury item than the others, with woven cable housing and a case that is ready for you iPod as well. Harman Kardon is just batting out of their league here, and Ultimate Ears doesn't improve on their cheaper models, even introducing some pretty terrible cable noise.

If you're looking to get the most out of your MP3 player, you'll have to spend some money. But as it turns out, the general rule is that once you pass about $100, your audio improvements will become smaller and more expensive. After reviewing all of these earphones, one simple fact is very clear: If I were in the market for a new set of earphones, I would buy the SE110s.