The online chat is actually sent through Microsoft's Xbox Live servers, over
the Internet. The audio is data compressed and may not be of very high sound
quality. This will depend on your location, local Internet traffic, etc. 

You may find that chat channel voices coming over the headphones sound 
"like robots" or "computery." You are hearing the chat channel with full 
high-fidelity reproduction, possibly for the first time - and yes it does
sound a bit "digital." This is normal for the Xbox and Xbox 360. 

The reason is that the voice channel is transmitted at a very low
bitrate/sampling rate, sort of like a heavily-compressed MP3. There is not
much bandwidth available for chat transmission and reception, so the sound 
quality has to be compromised a bit. Again, this is normal for the Xbox and 
not a problem with the operation of the X2 microphone or headphones. 
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