how do they work? and why are they not compatible with all players?

quick question: What is the best pair of noise-cancelling headphones?

http://www.edigital-store.com/odyssey1000.html Supposed to start shipping during "the holiday season" (now?). Copied from the site above; Features * 20 GB hard drive holds up to 500 CD’s worth of music * High-speed download (Up to 8 MB per second with USB 2.0*) * MP3 & Windows...

What are some solutions for splitting the output of a single speaker out to multiple devices? I intend to use this with a laptop, so my friend and I can watch a movie without disturbing others. I wouldn't rule out doing this with more than two people in the future though.

Can't get a pair of KSC-35's because of ebay problems on my end, so I'm gonna get either some KSC-50s or 55s. On one hand, the KSC-50's are very portable but the clips are kind of painful/unsecure I hear, on the other the KSC-55's have a secure headband but can't easily be slipped in the pocket...

Apple says this about them: Quote: Headphones Earbud-style headphones with 18-mm drivers using Neodymium transducer magnets Frequency response: 20 to 20,000 Hz Impedance: 32 ohms Sensitivity: 104-dB sound pressure level at 1 mW Apple also says the iPod has a Maximum output power...

I'm looking into buying a pair of headphones for my computer, mostly for gaming but also for music (mostly industrial, some classical and bits of techno here and there) and a little bit for movies. I was thinking about getting the Beyer DT250-80 but after reading a review posted here I'm not too...