Originally Posted by Sir_Homer
Yeah but is the fact that they do not require batteries because they DON'T have active noise cancelling, or that they can draw enough power from the jack?
They use passive noise cancellation, which is far superior to active noise cancellation because of lower weight, smaller size, doesn't need batteries, does a much better job of blocking external noise, and doesn't color the sound with a lot of circutry. Imagine wearing a pair of foam earplugs. Now imagine if someone drilled a hole down the middle of those foam earplugs, and put a tiny little headphone driver where the hole was drilled. Those are what canalphones basically are.
Grado SR-80s are a nice entry-level headphone. They do not have noise cancellation at all. They are open headphones, so not only will they not block external noise, but they will also leak a lot of sound to your surroundings. Not recommended for airplane, bus, or train use.
If you go to an Apple store, they will be selling cheapo Panasonics, or Bose Triports / QuietComforts. You can buy them if you want, but I would do a lot of research on head-fi.org before you commit $200 to Bose headphones.