We previously reported a phenomenon where Apple-sold Harman Kardon SoundSticks lose a channel of sound.
Our older report noted that the "Sound" pane of System Preferences displays the message "'The selected device has no output controls" for some users experiencing this problem.
A new report from Conrad Gempf indicates that the problem may be specific to iTunes:
"This problem [Ed.- sound disappearing from one channel] happened to me, running Mac OS X 10.3.2 with the speakers plugged straight into the USB port on the side of the computer rather than through hubs. I have a song in my iTunes collection which is supposed to start with guitar strumming in one channel (the missing one) and then gets joined by other instruments in the other channel. Playing the song yields silence until the other instruments come in if I play it through the SoundSticks. But if I remove the USB cable mid-song, strumming comes out of my PowerBook speakers. Plug in again -- silence.
"But then, just on the off chance, I decided to play the same track through Audion [Ed.- an MP3 and CD player/recorder] rather than iTunes. Much to my surprise, it came out perfectly from the SoundSticks. Versions are Audion 3.02 / iTunes 4.2.This suggests that the problem is not with the sound drivers as most web forums speculate, but something to do with iTunes. Having said that, I still have no balance control in System Preferences, which is odd if it's purely iTunes."
Separately, but almost certainly related, a thread on Apple's discussion boards reports problems using the SoundSticks with GarageBand - generally when the SoundSticks are not connected directly to a Mac, but rather through a USB hub.