My hypothesis on the heavy bass was to discourage the audience from taking videos of the performance. The sound on the videos I took (as well as some found on youtube) was barely discernible due to the level of the bass. I can't even hear any lyrics...just bass.
I'm guessing the recording equipment for the official video probably didn't have any of these issues. Looks like FIRST didn't want too much of the performance revealed before its official debut on TV.
