mastering sub bass

I wouldn't rely on FCP for that task. A good audio application would be much more suited. But if all you have is FCP, try adding the Graphic EQ filter and lowering the low end frequencies. A Compressor/Limiter may help as well.

-DH

Oh twilson_music.... the trick is to feel, not hear it!

Ask yourself this? .... Is your system up to it?

The Mystic North