Speaker w/F.R. 100hz & Receiver Bass crossover

Divide the length of the longest wall in your listening room into 565. It gives you the lowest frequency your room will accomodate.

For instance, a 10x12 room is good for 565/12=47hz

You want the full frequency range provided: to extend to the 47hz. Some recorded material will have moments below, but it will only cause distrotion in the room and adversly affect all other frequencies.

The point of XO'ing lower frequencies to a larger driver, as from tweeter to midrange, is it is better designed for specific frequencies. At the same time, it relieves the companion drivers from the burdeon of frequencies beyond its range, so each perfroms better in the range it designed for.

In high end audio, one of the goals is to achieve a seamless integration throughout the frequency range. Those that do, tend to be systems with an active, instead of passive, XO (cross-over): a powered unit that resembles a preamp.

If you are interested in really getting into audio as a private party listener, check out http://www.linkwitzlab.com there is a wealth of knowledge on all things audio worthy to be considered a valuable research source.

Both the subwoofer, and the main speakers will produce significant sound beyond their respective crossover points. (The cutoff is gradual). The different LF response specs may just reflect different people writing the spec, and anyway, the difference between 80 and 100 Hz is not a big deal.

Didactically, view your system thread to see my final post. I think that it sums everything up. If others would care to see it, please go there.