Jeremy,
That would be the case if you had your speakers attached to the Mac and you were not monitoring video with a video monitor. This is the case for maybe doing some offline work or portable work.
Not everyone works that way all the time.
Many editors DO monitor video on an external monitors at all times while cutting in their studios. In that case, the speakers should be connected to the DV Deck/DV Camcorder or the outputs of the Video Capture Card/Breakout box and not the Mac.
Every time someone has issues with audio, it usually breaks down to if they are monitoring video externally or not monitoring video at all, and in each case, it is crucial to have the speakers are connected in the proper location.
Since I use audio from other apps and like to monitor video externally, I like to patch both my DV Deck and Mac audio to a Mackie 1202 mixer and then attach the speakers to that. That way, I can monitor audio in any situation. I recommend this scenario for everyone that cuts with FCP in the pro realm.
Kevin Monahan
Author – Motion Graphics and Effects in Final Cut Pro
fcpworld.com