This is a very interesting thread because I'm also dealing with similar issues, so the information here is valuable.
Let me throw in my 2 cents. I have Tyler Acoustic Linbrook speakers w/bass modules and I've measured their response in my room to go as low as 35-40 hz. I also have a JL Audio Fathom 10" sub. I ended up contacting JL Audio tech support to get more detailed information about setting the sub up for optimal performance. I was told by Barry that playing speakers full range and crossing the sub at the lowest octave would result in mish mash. He indicated that the best way to do it is to cross the sub at 80 hz using an external crossover, thus freeing up the main speakers. He said to conceptually treat the sub and mains as a two-way system. The sub being one way and everything else the other way. That leaves the Bryston that was mentioned earlier as a key component, albeit an expensive one. Barry also put a plug into his own external crossover he is developing for half the price as the Bryston, but it's not avail yet. Here is his website that explains more about getting a sub dialed in: http://www.soundoctor.com/whitepapers/subs.htm
One more thing, if I had to do it over again, I would have gotten the 12 or 13" Fathom instead of the 10". The 10" doesn't have enough muscle for some of the powerful classical music I listen to.
Let me throw in my 2 cents. I have Tyler Acoustic Linbrook speakers w/bass modules and I've measured their response in my room to go as low as 35-40 hz. I also have a JL Audio Fathom 10" sub. I ended up contacting JL Audio tech support to get more detailed information about setting the sub up for optimal performance. I was told by Barry that playing speakers full range and crossing the sub at the lowest octave would result in mish mash. He indicated that the best way to do it is to cross the sub at 80 hz using an external crossover, thus freeing up the main speakers. He said to conceptually treat the sub and mains as a two-way system. The sub being one way and everything else the other way. That leaves the Bryston that was mentioned earlier as a key component, albeit an expensive one. Barry also put a plug into his own external crossover he is developing for half the price as the Bryston, but it's not avail yet. Here is his website that explains more about getting a sub dialed in: http://www.soundoctor.com/whitepapers/subs.htm
One more thing, if I had to do it over again, I would have gotten the 12 or 13" Fathom instead of the 10". The 10" doesn't have enough muscle for some of the powerful classical music I listen to.