It's not about status or wealth or fashion, it's about fidelity. When your life's work is made of sound waves, you need to hear the truth and you need to protect your hearing. Truly great headphones provide both, and they're not as crazy-expensive as you might expect. If you love music, read on and learn how to hear like you've never heard before.

Fair warning: You may be perfectly happy with the quality of your iTunes library the way it is. After listening to a few tracks on the world's best headphones, I guarantee that you will want to re-rip every one of your CDs and upgrade any songs you have purchased from the iTunes Store to iTunes Plus. Generally speaking, anything rendered at lower than 192 kbps, in MP3 or AAC format, will sound somewhat shabby on pro-grade headphones. However, once you've upgraded your library to 256 kbps, you will enjoy subtleties in your music you never imagined -- and you'll find yourself listening at lower volume levels too.

Impedance and sensitivity
You might think you can simply jack your studio-grade headphones into your iPod and achieve sonic bliss, but it ain't necessarily so. Most top-shelf headphones are designed to work best with hot amps and mixers that put out a lot more clean power than an iPod, laptop, smartphone, or portable CD player emits. There are compact, battery-powered headphone pre-amps that take care of the mismatch nicely, making any headphone sound as good as it possibly can. We like and recommend the Total AirHead ($99) but there are other mobile pre-amps out there.

How can you tell if a headphone will mate well with your mobile audio device and not need a pre-amp? Two terms to know: impedance and sensitivity. Without geeking out on you, I'll say that all you need to know is that the impedance should be low and the sensitivity should be high. Some manufacturers omit sensitivity ratings from their product descriptions, so often all you'll have to go on is impedance. Generally speaking, you want your impedance to be under 75 ohms. There are some exceptions but that's a good rule to work with.

The rub of low-impedance "cans" is that they aren't the absolute best sounding headphones in the universe. Great headphones need a lot of power and that usually means the impedance is high. Don't get me wrong -- there are some fantastic-sounding low impedance models out there that most people will swoon over. But the very best have impedances in the 200-300 ohm range. This makes testing and choosing them difficult, as there is a trade-off between mobility and performance. There are high-impedance headphones that are so sweetly good we simply had to include them, with the caveat that they need a preamp, adding $99 to the price.

Around the ear, on the ear, and in the ear
There are essentially three types of headphones: The classic big ones that go around your ear and rest against your head are called circumaural. These are the classic old-school cans you see recording artists wear in the studio. They come in two styles, closed-back and open-back. Closed-back designs provide isolation from the outside world and do not bleed sound out to your surroundings. The obvious benefits are that you hear only your music and no one else hears it. Recording artists always use closed-backs so they can hear the track they are playing or singing to but the ultra-sensitive studio microphone doesn't hear it. Open-back designs have a more natural sound; they are in essence a pair of small monitor speakers hanging in the air in front of your ears. With few exceptions, audiophile-quality headphones are open-back. They bleed all over the place and they block almost no sound from the outside world from mixing with your music, but they sound spine-tinglingly glorious. If you listen alone in quiet places, get open-back headphones.

Another common design you'll find are designed to sit directly on top of your ears. Called supraaural, these cans block a little more from the outside and bleed a little less than open-back circumaural designs. We did not include any supraaural models in this round-up for three reasons: (a) Grado, the top maker of this kind of headphone, chose not to participate -- which is no big deal because (b) I think they look funny and (c) in over three decades of hanging around in recording studios I've never seen anyone wear them.

In the last five years or so there has been a huge amount of interest in a style of headphone that was developed for discreet stage monitoring. They are variously called in-ear or canalphones but they are are the same thing. These are tiny little plugs that insert directly into your ear canal, like a hearing aid. Properly fitted, they virtually disappear. The very best sounding designs use multiple tiny speakers (also called drivers in pro audio lingo) to separate the highs from the lows for better fidelity. They are always low impedance and have high enough sensitivity for direct connection to iPods and other low-ouput devices.

In-earphones are not for everyone. They take a while to get used to and can be a bit fiddly to fit correctly. They are also harder to live with since you have to carefully insert them rather than just pop them on your head like big cans. When you take them off, you don't want to just throw them in your pocket. They are delicate little mechanisms and should not be exposed to hard knocks and dirt -- and you don't want to stick a dirty object directly into your skull everyday. You need to be a bit fussy and keep them in their sealed case.

But the rewards are worth it. In-earphones offer the best isolation of any kind of headphone, both internal and external. They are easy to take along because they are so impossibly small. You can listen privately in public without announcing to the world what you are doing. And best of all, the top models sound stunningly gorgeous.

The precursor of the in-earphone was the earbud, the design that comes with every iPod. Earbuds are small, handy, somewhat stealthy, and sound bloody awful. Muddy lows, missing mids, tinny highs -- no thanks. Life's too short to wear earbuds.

World's Best Headphones for iPod
I have combined all headphone types into a single list. Choose the style that you think would best fit your lifestyle, then decide how much it is worth to you to actually hear all of the music you love. Sticker shock is normal in this range, but you only have to pay once for the best, versus buying mediocre things over and over again. There are some relative bargains to be found at the end of the list, but remember: It's about sound, glorious sound -- as much as you can get for what you can afford.

Best circumaural open-back headphone with a pre-amp: AKG K 701 and Sennheiser HD 650
We have a tie for best sounding headphones. The AKG K701 ($450 list, $310 street) and Sennheiser HD 650 ($500 list, $350 street) are both so exceedingly great that choosing between them comes down to which one fits your head better. To me, the Sennheiser fits a little snugger yet feels lighter than the AKG, but almost imperceptibly so. If you prefer a headphone you can wear for very long periods, then you may find the AKG a tad more comfy. People used to wearing tight-fitting studio cans will probably like the Sennheisers better. There are also the dramatically contrasting aesthetics to factor in. The AKG is an eye-catching design in white and grey like your iPod, with an auto-adjusting brown leather headband that is classy looking and supremely comfortable. The Sennheisers are dark grey and black, with an austere old-school look that audio pros will prefer. Whichever you choose, you can be secure in knowing that you are wearing the best headphones on the planet. Don't forget to factor in an extra C-note for a headphone pre-amp -- you'll need it when you want to take all that goodness outside.

Best circumaural closed-back headphone with a pre-amp: beyerdynamic DT 770
If you want stunningly accurate sound but need isolation, buy the beyerdynamic DT 770 ($319 list, $269 street). These sweet cans offer the sound of beyerdynamic's top open-back model (the brilliant DT 990) but with the benefit of keeping all that goodness to yourself while you shut off the world around you. My friend Lance Taber is a principal guitarist/producer behind the smash-hit Guitar Hero series of computer games, and he always does his final mixes wearing his beloved DT 770s. This is a man with golden ears who can have any headphone he desires -- need I say more? Yes: Don't forget the pre-amp.

Best circumaural open-back without a pre-amp: beyerdynamic DT 860
Beyerdynamic doesn't make a big deal about it but they produce the best headphones you can buy that don't require a pre-amp. Perhaps they should be shouting it from the rooftops. With so many millions of iPods piping perfectly sweet music into crappy $5 earbuds, there is clearly a market for upgrades. Our favorite in the unpre-amped category is the DT 860 ($319 list, $269 street). It offers superb sound, clean aesthetics, durable design, and folding ear cups for easy packing. Just plug them into your iPod and hurl those little white earbuds into the dumpster where they belong.

Best circumaural closed-back without a pre-amp: AKG K 271
Go into any pro recording studio and you'll find the AKG K 271 ($270 list, $190 street). Dead accurate, incredibly durable, extremely comfortable, and reasonably priced. They offer excellent isolation for recording use, or just to keep street noise out of your Beethoven string quartets. They also mute themselves when you take them off -- how cool is that? Chances are good that many of your favorite songs were recorded by musicians wearing these cans. They have a removable locking cable since it's the cable that wears out first in constant professional use. It also makes them easier to pack and store. They drive well jacked directly into iPods. What's not to love?

Best in-earphone: Shure SE530
Want to make the world go away and drift into a perfect world of sound so powerful it makes the hairs on your arms stand up? Pony up for a set of Shure SE530 ($499 list, $359 street) in-earphones. Shure pioneered the in-ear monitor for musicians to wear on stage, so they've always delivered units that offer not only professional-grade sound but that are absolutely reliable -- every gig, tour after tour. When musicians started taking their in-ears with them to the tour bus after the performance, it became clear there was a market for in-earphones beyond the stage. Now there are several companies offering in-earphones but we think Shure has the edge. The SE530 uses three discrete micro-drivers: one for the highs and two for the low frequencies. The result is balanced, audiophile-grade performance unlike anything that has come before. It comes with a fit kit to make it easy to find that balance of comfort, performance, and isolation. Forget the noise-cancelling headphones you see from Bose, Sony, and others. If you want to really get away from it all and hear your music exactly the way it was recorded, you want Shure SE530s.

Best bargain in-earphone: Ultimate Ears super.Fi 5 Pro
While two hundred bucks is not what most people would call a bargain for a pair of earphones, true music lovers on a budget will be glad to pay it to get what they need. If you can't shell out five bills for the glorious triple-driver Shure SE530 in-ears, get Ultimate Ears super.Fi 5 Pro ($249 list, $189 street) in white, black, or clear (our favorite.) They offer the best performance you'll find in dual-driver in-earphones, with a smoothness that makes you want to listen for hours. They are easy to fit compared to most of their competition and the clear model with the cords wrapped over your ears and behind your neck make them essentially disappear, Secret Service agent-style. They don't insert quite as far as other models in this range, making them great for those who are new to in-earphones. These are remarkably sweet little cans for the money.

Best bargain circumaural without a pre-amp: Sennheiser HD280 Pro and Audio-Technica ATH-A700
Another tie, ladies and gentleman. The Sennheiser HD280 Pro ($199 list, $99 street) is a staple among recording musicians who need to spend their money on reference monitors rather than headphones. They are unbeatable for the $99 discounted price and can be easily driven directly by an iPod. They are reasonably comfortable and seal very well. If you need great sound and isolation on the cheap, get the HD280s. If you needs lean more toward listening than creating music -- and that music tends to be bass heavy -- then you'll find satisfaction in Audio-Technica's ATH-A700 closed backs ($299 list, $119 street). These attractive, oversize yet plushly comfortable cans offer specs and features usually associated with models costing twice as much and for the most part they deliver what the marketing language promises. To my ears, they sound a bit boomy in the bass which overrides the rest of the frequencies to an extent. You may like this hugeness, however. And you can always dial back the bass on your amp or iPod if it gets to be too much of a good thing. Still, a good value at $119.

Headphones don't have to cost a fortune to be good. These discount stereo headphones offer stylish design, an emphasis on sound quality, and won't set you back hundreds of dollars.