It's no secret that these days, small files can reproduce sound with amazing quality. Of course, that sound will only be as good as the speakers you hear it from, and the earphones that ship with the iPod just aren't that great. There's good news, though: they're removable. Just swap in a new pair and you'll get a totally different experience!

It was more than two years ago that we ran our first in-ear headphone buyer's guide, and the response from you, the readers, was terrific. A lot has changed since then: improved technology, new models, and more vigorous competition (and cooperation!) among manufacturers. That's why we decided it was high time that we catch ourselves, and all of you, up on the latest and greatest.

You may notice we review some pricey products in this guide, since we'll cover headphones between $40 and $900. If the sticker-shock turns you off, consider this: the highest-end earphones in this guide come darned close to the listening experience in a professional music studio. In building a studio you pay thousands of dollars for amps, speakers, and cables. That's to say nothing of the tens--maybe hundreds--of thousands of dollars for the careful design and construction of the room itself. So imagine: for a few hundred dollars you can approach the listening experience of your favorite band as they were mixing your favorite album. For musicians, high-end earphones are the cheapest sound setups available if you want to start mixing your own recordings.

With that in mind, we've decided to stick to the "in-ear" style, that is, models that completely seal the ear canal. We focus on those models because they're among the most popular, are extremely portable, offer good isolation from external noise, and run the gamut of price and quality. If in-ear headphones aren't your thing, there's always earbud, ear-covering, and noise-canceling models to consider.

A word of caution: just because these headphones seal out external noise doesn't mean your ears are safe. You're putting miniature speakers in there, which can put you at risk of hearing damage. We recommend you consult an audiologist regarding safe listening levels.

Finally, make sure you check the most current pricing as you compare the models below. At press time, many of these models were selling for little more than half price, making some of our favorite picks (including the ER6i, FS1, Super.fi 5 Pro, and ER4P) incredible bargains.

Important Factors

So we spent the last couple months on a reviewing binge, experimenting, testing, and even having GOOP poured in our ears. Our conclusions? Mileage definitely can vary, depending on several important factors.

Comfort: Each earphone model has a unique shape, and so does each pair of ears. What fits one person well doesn't necessarily work for the next. First, you need to make sure your selection won't hurt once its in your ear. But it's also crucial to get a good seal, because a good seal improves bass response--in fact, some earphones even rely on bone conduction to properly reproduce the low-end.

Cable Design: Some earphones have cables that simply dangle down from your ear, while others wrap up and over the ear, falling behind your head. Choosing a style may be a matter of comfort and convenience, since air travelers, runners, and home studio musicians all have different needs. But it's also a matter of sound quality. Be aware of "microphonics," the thudding noise you hear when you tap or rub the headphone cable. Over-the-ear models stay better anchored, particularly when moving about, and so tend to suffer less from microphonics.

Universal or Custom Fit: The earphones that come with your iPod are considered "universal" fit -- that is, they'll fit in just about any pair of ears. It is possible, however, to get molds custom-made to fit your ears (and only your ears). These fit perfectly, until your ears change (which may happen over many years). Custom earphones seal (and therefore sound) much better, dramatically reduce microphonics, and are far more comfortable. They make for a much more pleasurable listening experience -- but they hit the wallet much harder.

Headphone technology: Believe it or not, earphones are made with anywhere from one to three speakers in each ear. There are also differences in the speaker technology (dynamic and balanced armature are the most prevalent). Different companies will tell you different stories about how many drivers or which driver technologies are the best -- depending, of course, on what they sell. In our experience, lingering on the technological details wasn't worth too much time: we just put 'em in the head, cranked 'em up, and obeyed the ol' ears.

The first part of this buyer's guide is about universal fit models -- we'll round up the custom-fitted models in part II. We've chopped this article into 3 sections, by price range. With that, we're off!

This category is by far the most crowded. We chose to focus on the same manufacturers as in the higher price categories, since those companies often supply components to other headphone brands. The exception is Sony, whose products we included based on their popularity.

Model: INTERSHOP.enfinity/eCS/Store/en/-/USD/SY_DisplayProductInformation-Start?ProductSKU=MDREX71SLA/B/STAR&Dept=audio&CategoryName=pa_Headphones_FontopiaEarbud">Sony MDR-EX71SL and INTERSHOP.enfinity/eCS/Store/en/-/USD/SY_DisplayProductInformation-Start?ProductSKU=MDREX90LP&Dept=audio&CategoryName=pa_Headphones_FontopiaEarbud">MDR-EX90LP
Price: MSRP US$50, $100 -- Sony is the hottest contender in the region $100 and below. Sure, you could go for the $15 Koss Plug or the $40 Apple In-Ear Headphones, both of which we reviewed in our last guide. But the Sony models are particularly popular, and for good reason: they're a good value.

Both of these headphones are geared toward pop, rock, and hip hop listeners, and use single driver, dynamic technology. Their dangling-cable design, easy-to-insert shape, and surprisingly mild microphonics make them great for commuters and casual listeners. The more expensive EX90LP have a big bulb that sits in the outer ear, which may annoy some, or make finding just the right seal more difficult, but we didn't have any problems.

The sound of the lower-priced MDR-EX71SL is fine for most modern music, if you like it bass-heavy. But the lows are woofy and the mids get lost. Classical recordings in particular will sound completely unremarkable. Jazz or old-school country tracks sound little better. The MDR-EX90LP have a much better balance, with much clearer mids. But the bass is still a little mushy. If you want big, tight bass, your best bet will be to shell out another $50 for the FS1 (XtremeMac).

Fit: Easy insertion and decent seal. Surprisingly low cord noise (microphonics) for dangling-cable design.

Sound: Big low-end and decent overall sound for the price. Woofy bass, which is overpowering in the EX71, but which the EX90 reigns in. For a clearer sound, look to the Shure or Etymotic products.

Model: Shure E2C
Price: MSRP US$100 -- Anyone who's worked with audio has heard the name Shure, and anyone who performs has certainly seen their microphones. But Shure is relatively new to the in-ear headphone game, and they're competing aggressively in all price ranges, in order to be considered one of the go-to manufacturers. The E2C is their entry-level product, and while it sounds completely different from the Sony products, it certainly holds its own.

All of Shure's products have an over-the-ear cable system, with a way to discretely capture the cable in place behind the head. They also offer both silicone and foam sleeves, both of which provide an easy, comfortable seal. The E2C has a BIG bulb, but it's lightweight and sat comfortably in the outer ear.

Like the Sonys, the E2C is a single-driver dynamic headphone, but it has a much clearer sound. They lack the bass punch of the Sonys, and have a distinct bump in the mids, but the bass they reproduce is tight and clear. If you're not a low-end freak, these are overall the best sounding headphones we've heard below $150.

Fit: Silicone or foam sleeves. Easy insertion and over-the-ear cable design.

Sound: Weakish on the low-end, with a bump in the mids, but the overall sound is delightfully clear. Tight bass, rich sound throughout.

Model: Westone UM1
Price: MSRP US$110 -- Westone makes some great music products, and they're well known in the in-ear headphone market. Their entry-level, single-driver UM1 compete most directly with the E2C (Shure). They use super-comfortable foam sleeves, and also have an over-the-ear design. Unfortunately, the bass is even weaker on the UM1 than on the E2C. For our money, we'd look elsewhere.

Fit: Extremely comfortable foam sleeves. Smaller aperture makes for less frequent cleaning than the E2C (Shure).

Sound: Weak on the low-end, and a hazier sound than the E2C.

In many respects, this is the sweet-spot for in-ear headphones. The sticker-shock is still survivable, and the sound quality is head-and-shoulders above the entry level products covered above. Even if you're a casual, non-audiophile listener, these products will make you feel more immersed in your music. That's because these models tend to offer good stereo imaging, good clarity across the frequency spectrum, and respectable low-end. If you're looking for the least-expensive way to rediscover your music collection, this is it.

Model: Etymotic ER�6i
Price: MSRP US$150 -- Etymotic has cut out a unique spot in the headphone business. They're one of the original in-ear headphone makers -- actually, they started out making hearing aids -- and they tend to cut their own path. The ER6i are a tweaked -- and $10 more expensive -- version of the ER6, which we reviewed in the last guide. The only difference is a bump in the low frequencies, which give the ER6i a little more heft in the bass -- it's subtle, but it does help the 6i perform better in some environments -- like when walking or commuting -- where microphonics can be an issue.

Speaking of microphonics, all of Etymotic's headphones use a dangling-cable design that can result in a lot of cord noise. We were disappointed, until we learned the subtle art of clipping the headphone cable at just the right height on the chest. This puts a little slack in the line, and eliminates both the microphonics and the downward pull on the ears. Of course, if having a headphone cable clipped to your shirt isn't hip enough for you, look elsewhere.

The ER6i, like the ER6, sound excellent -- they're even and clear across the frequency spectrum. The only problem is that many listeners don't want an even sound, they want a big sound. If you like to rock out to your music, you may want to look at the Sony or XtremeMac products instead. (Or, if you want a nice middle ground -- clear, honest sound with a little more punch -- try the Shure E3C, which we reviewed in the last guide.) But if you like a nice, clear sound with great isolation from ambient noise, the ER6 and 6i do a great job of it. They're also best-in-class if you listen primarily to Jazz and Classical, or to spoken word content (like audiobooks or podcasts).

A final word on the ER6 and 6i: while they're great for consumer music listening, their precise sound and great isolation make them a perfect prosumer-level set of mixing headphones. If you're looking for an audio engineer's sound system on the cheap, you'll do best to look to Etymotic's product line.

Fit: These are tiny! The only universal model we'd consider trying to wear while falling asleep on a plane. Dangling-cable design requires clipping cord to your shirt to avoid microphonics.

Sound: Nice to have a choice between the ER6 and the low-end-bumped 6i. Beautifully clear, true sound that will please critical listeners across genres. Their sonic honesty also make them great starter headphones for budding audio engineers.

Model: XtremeMac FS1
Price: MSRP US$150 -- Given its price, our first reaction to the FS1 was: "Wait...seriously?" We've got some in-depth comments, but here's the bottom line: the FS1 sounds terrific. In fact, depending on your taste, you could argue that it crushes everything up to double its price, and competes aggressively with the most expensive models in this guide.

XtremeMac is not an audio company. The FS1 is due to a partnership with FutureSonics, which goes head-to-head with the other high-end headphone makers. They can be worn over or dangling from the ears, and use a single-driver, dynamic technology. It's that last bit -- the "dynamic" part -- that make the FS1 so unique: dynamic speakers are much better at reproducing low-end. Usually great low-end, though, means a muddy middle that obscures all the highs. (See the review of the Sonys, above.) Somehow, FutureSonics figured out how to massage that middle range into an astonishing growl, which easily competes with the stratospherically priced E500 (Shure).

It took us a lot of a/b-ing among competing models, but we did find some limitations of the FS1 sound. For those who listen primarily to jazz and classical music, the FS1's extraordinary bass can get tiresome -- though it never sounds bad, so casual listeners of those genres might not mind. If you're looking for a recording engineer's set of headphones (to try your hand at mixing music), the ER6 or ER6i (Etymotic) will give you a more honest reproduction.

Fit: Nice to choose whether cables dangle or go over-ear. Flanged silicone or foam sleeves.

Sound: Mind-blowing low-end, without sloppy bass or muddy mids. Non-ideal for classical, jazz or music engineering, but great for commuters, travelers, active listeners. For rock, pop, and hip hop this is best-in-class sound -- and might be best in the next class's sound, too.

Model: Ultimate Ears Super.fi 5 Pro
Price: MSRP US$250 -- Ultimate Ears has a tendency to make products with a distinct sound. It isn't as intellectually pristine as Etymotic's, nor as fierce and growling as XtremeMac's, but they are delightful to listen to. There's an intimacy to the Ultimate Ears sound, as if the music is being whipped up just for you, on the spot. At the same time, music takes on a spaciousness, working against that "inside your skull" feeling that you often get listening to headphones. It's a matter of taste, but frankly, we love it.

The Super.fi 5 has easy-to-insert silicone sleeves (foam sleeves are also an option), and a clever twist on the over-the-ear cable design. right at the earpieces, the cable keeps its shape when you bend it (think Gumby, in cable form), so it hugs your earlobe a little more snugly than other headphone designs. The Super.fi sticks straight out of the ear, though, making them harder to keep in comfortably while, for example, trying to sleep on a plane ride.

As for the sound, it's great. A warm, rich bass -- though not nearly as punchy as the FS1 (XtremeMac) -- creates a solid foundation for clear, detailed mids. The highs are incredibly rich, so drum kits' metal surfaces take on a shimmer, and vocals have a textured complexity.

Fit: Easy to insert, and stay put better than any other model, thanks to moldable over-the-ear cables.

Sound: Best in class sound, but with a different character than the FS1 (XtremeMac). More appropriate for anyone with broad listening tastes. It's not as precise as the ER6 and 6i (Etymotic), but it's got more character.

Model: Westone UM2 and Shure E4C
Price: MSRP US$300, MSRP US$300 -- The UM2 and E4C are stuck in an odd spot, priced between the prosumer and pro levels. The ER4P (Etymotic) cost the same amount, but we put them in the pro category because they have a very unique sound and function. These headphones, though, compete most directly with the Super.fi 5 Pro (Ultimate Ears), so we put them in the prosumer category.

Both the UM2 and E4C have a comfy fit -- though the E4C has a band of metal that sits against the ear and may strike some as unpleasant when cold. They also sound great. Both have a nice warm low-end, just like the Super.fi 5 Pro. They have clear, even mids, just like the Super.fi 5 Pro. But they don't quite have the same detail and depth in the highs as the Super.fi, and unfortunately, they cost about 20% more. There's absolutely nothing wrong with the fit or sound of these headphones -- indeed, if you bought them without comparing against other models, you'd certainly be impressed with the sound. But with the other terrific choices in this category, we find them hard to recommend.

It seems that the rules for prosumer headphones are going to have to change, thanks in large part to the aggressively priced FS1 (XtremeMac). It looks like the competition will have to reset its expectations about what it can charge for prosumer level sound quality.

Fit: Both models are very comfortable, with an over-the-ear cable design. That cold metal ring against the ear on the E4C may feel unpleasant to some.

Sound: Solid sound for this category. Not quite as much detail in the highs as the Super.fi 5 Pro (Ultimate Ears), not as much tightness in the bass as the FS1 (XtremeMac).

This category has been seriously energized since our last buyer's guide on earphones. Each model sounds unbelievably good -- rich bass, clear mids, and detailed highs. They also sounds completely different from one another. This segment is a lot like fine wines: they all taste great, but if you pair them with the right meal, they change your whole outlook on food. If you're thinking about purchasing a product in this category, you'll want to think seriously about what you want to use them for in order to get the most bang for your buck.

Model: Etymotic ER�4P
Price: MSRP US$300 -- Ety's flagship in-ear headphones, the shotgun-shaped ER�4P, are without a doubt the hardest to get in your head -- it took us about a week to figure it out. (It involves yanking back on your ear so you can slide them very deep in the ear canal). Once there, though, they are pretty comfortable, and sound remarkable. Etymotic claims they get the most accurate earphones on the market using a single-driver, balanced armature design. We believe it: of all the models we tested, they best replicate the clear, precise sound of a professional music engineer's studio.

Outdoor and active users will want to look elsewhere: the dangling-cord design can cause bad microphonics if you move around a lot, and the three-flanged earpieces make a great seal, but actually whistle when the wind catches them. You'll also want to try before you buy, in case the earphone's deep placement makes you uncomfortable.

At $300, these are the lowest-priced pair in this high-end category, but from a strict audio reproduction perspective, these are the best of the bunch. They also dramatically outperform the similarly priced UM2 (Westone) and E4C (Shure). The downside is that anyone looking for a throbbing low-end will be disappointed. But if you're looking for a no-nonsense, honest sound -- for example, if you want earphones to mix your own recordings -- the ER4P are your best bet.

Fit: Insertion is more involved than usual, and the deeper seat may be weird to some. Certainly an unusual fit, so try before you buy.

Sound: Best for classical, jazz, at-home listening, and budding engineers in need of a sound system.

Model: Ultimate Ears Triple.fi
Price: MSRP US$400 -- The UE Triple.fi are not yet in full production, so we could not perform a complete comparison. We did, however, get to listen to the final prototype at the Podcast and Portable Media Expo last September. We'll amend this entry with the full review as soon as the product is available for testing, but for now, we'll give you our on-the-spot reaction from our brief test.

The triple-driver, balanced armature Triple.fi have a sticking-out-of-the-ear shape but an over-the-ear cord design, so they set comfortably and the insertion is easy. If our brief experience with these earphones is any indication, these will provide the best stereo imaging of any product on the market: each instrument sounded like it came from a precise, distinct location in space. Even better, Ultimate Ears has made great strides in getting the sound "out of your head" -- we felt like the sound was in the space around the head, rather than right inside the skull.

We don't expect the reproduction to be as austerely precise as the ER4P (Etymotic) or as in-your-face as the E500 (Shure), but these should make an exciting addition to this product category once they're available. Check back -- probably in January -- for a full review.

Model: Shure E500PTH
Price: MSRP US$500 -- At $500, the E500 is the most expensive universal model we tested. They have a plump, solid casing, with silicone seals. They're easy to insert, and are quite comfortable once there. The over-the-ear design keeps the buds well in place. And then you turn them on.

Wow. The E500, also a triple-driver, balanced armature design, sound HUGE. A hot low-end, rich mids, and open, easy highs. If you want a pair of earphones that replicate feel of a 2.1 sound system with the detail of pro audio, this is your product. True to its image, Shure has made fantastic earphones for rocking out. We found that the sound felt packed inside the brain, since the stereo imaging isn't as open as the Triple.fi (Ultimate Ears). The bass is also wetter and less punchy than the FS1 (XtremeMac). And they are not as pristine sounding as the ER4P. These are not, in other words, your grandma's earphones -- nor your audio engineer's. These are for listening while shaking the hump.

About $70 of that fat price tag goes toward the PTH -- or "Push-to-Hear" -- feature, which at the flip of a switch cuts the volume of your music and activates a lapel mic so you can carry on a conversation without removing the earpieces. It's not the hippest gadget, but if you don't mind looking a little geeky, it works well. Just be careful not to blow into the lapel mic: we darn near blew out our ears that way.

Fit: Nice fit, easy insertion. The earpieces are large, but sit pretty well in place.

Sound: Huge! Gets your body moving -- great headphones for active users. FS1 (XtremeMac) gives it fierce competition in rock, pop and hip hop, but the E500 beats the FS1 in other genres for its detailed mids and richer highs.

Model: XtremeMac FS1 (again!)
We reviewed the FS1 according to its price category, which at $150 is between consumer and prosumer levels. But its sound is so unique -- and so good -- that we have to compare it to the models with which it's actually competing.

Simply put, the FS1 has the tightest, punchiest, best bass of any of the models we've reviewed above. But in the pro category, that's not always the point. The ER�4P has an edge on the FS1 as a more precise sound, and are better for classical, jazz, and audio engineering. The Super.fi 5 Pro, and presumably the oncoming Triple.fi (Ultimate Ears) have more detail in the highs and a richer sound stage.

The product the FS1 hits hardest is the E500. Shure's flagship product is at its best when you're rocking out, and while it holds an edge with richer tones and greater detail in the upper registers, its bass sounds anemic and mushy next to the steamrolling sound of the FS1. Not that there's no reason to buy the E500 -- it sounds exceptional -- but the FS1 is proof positive that price isn't everything.

So that's that: a whirlwind tour of the universal fit models of in-ear headphones. We know we didn't cover every model out there, so if you know of others, or want to offer your opinion on any of the models we covered above, dive into the comments below. Also, keep an eye out for part II of our guide, which will look at the Cadillac cars of personal audio: custom-fitted headphones.