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If you're like most music fans, you probably listen to tunes on your iPod or a laptop computer. One day, you decide to take a step up and buy a pair of high-end headphones. But when you plug them into iPod, the music sounds awful. The volume stays low even when it's maxed out, and there's even a bit of static-y distortion. What gives? You've probably fallen victim to mismatched impedance.
To put it simply, your high-end headphones sound bad on an iPod because the iPod can't give them enough juice. It's a lot like trying to use a flashlight with dying batteries. Some high-end headphones need a lot of power, and they can't do it on an iPod's tiny battery.
While this is a gross oversimplification of the concepts at play here, checking the impedance of a set of headphones should give you a clue about how it will work with your iPod.
In simple terms, impedance refers to the headphones' ability to resist electricity. The higher the impedance, the more voltage they need. For most iPods, you should shoot for headphones with an impedance of about 40 ohms.
Generally, headphones' impedance should be 8 times the output impedance of your source. So for a 5-ohm iPod, the sweet spot is 40 ohms. A few ohms over or under the ideal level should be fine.
Let's see how this applies to some popular high-end headsets:
The best thing to do is to buy headphones to match your media player. If you do this in the first place, you will have few (if any) problems.
If you've already bought mismatched headphones, you can buy a portable amplifier to boost your media player's output. On the high end, there's the V-Moda VAMP DAC/amp combo, designed for the iPhone 4 and 4S. It works particularly well with 300-ohm (and higher) headphones, and doubles as a battery pack. But at $650, it costs a pretty penny.
Otherwise, there are plenty of affordable, portable amps on the market currently, like the FiiO E6. They're designed to boost your media player's volume, but they'll chew through battery life even quicker than usual if you're using high-impedance cans. And who really wants to carry around a bunch of extra junk in their pocket?
Always buy your device first, then buy headphones to match. While you may not be a fan of low-impedance headphones, those are, by design, more compatible with newer mobile devices, and the most efficient option when looking for something to pair with your iPod or smartphone. If you absolutely must pair a set of high impedance cans with your iPod, there are no cheap or convenient options for portable use. You have been warned.