Jeff, Are you sure? From everything I've read, 80Hz is a pretty safe choice because frequencies below that point are extremely difficult (if not impossible) to localize.

That said, I think Bob Stuart (of Meridian) claimed that while we can't perceive direction we can sense bass envelopment down to something like 40Hz. By 'envelopment' I mean the mono in-your-head bass vs externalized sounding bass that seems to surround you. This is probably why Lexicon's Bass Enhance processing works on frequencies below 80Hz.

Sanj