You will find kick drums, oboes, pipe organs lower end and a few
other instruments down around 60Hz. 
        I experimented with various sub woofers over the past few years
and built several based on the Hsu cylidrical design. I played with
crossovers and filters and found MY system sounded best when crossed
over at the sub at 50 to 60Hz. I also found that 40 to 50 Hz worked
best in my system for Home Theater Applications.
        But keep in mind that subs reinforce most mains in the critical
60 to 80 Hz range, if not carry the majority of the load depending on
what you are using for main stereo speakers. In my case my full range
towers have excellent bass extension, so I was able to cross them over
at a lower freq for best effect. I know the 50 to 80 Hz range may not
seem like much, but a hole anywhere in this range can make a really
excellent system sound like crap.
Hope this helps.
Cheers, John
Windows 95:  The bugs go in before the name goes on.
--- Maximus/2 3.01
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