This command brings up the Speakers dialog, which lets you assign surround speakers to a multi-channel audio file. The speakers are named according to the DirectSound specification. To assign a speaker, check the checkbox to the left of its name. Checked speakers are assigned to the available channels in order, from top to bottom. If any assignments are made, the number of assigned speakers should match the number of channels, and if this isn't the case, a warning is given.
If no speakers are assigned, a default assignment is made. For stereo audio, the default assignment is normally left/right, but behavior may vary depending on the audio device. Speakers can be assigned regardless of whether they actually exist in your audio setup.