Photos of internal iPad components released by the FCC have revealed a few surprises. Official iPad specifications from Apple do not mention stereo audio output, only a "built-in speaker." Further inspection of the teardown photos reveals what is clearly two distinct speakers.
The parts shown above comprise the speaker assembly, which consists of dual speakers to provide stereo sound. According to ifixit.com there are two small sealed channels that direct sound toward three audio ports in the bottom of the iPad. This is the first time evidence of stereo sound on the Apple iPad has surfaced.