Which subwoofer?

@bdp24 

Danny Richie uses a pair of OB subs in the front of his room and a pair of F12G's in the rear (in both his company's listening room and at hi-fi shows), the F12's in phase opposite that of the the OB's. I believe he uses 40Hz as the x/o frequency between OB and F12.

This is great to know! So he's using F12s up to 40Hz. Do you happen to know how high he crosses over the F12Gs?I guess I have some chewing to do: I run F12s to 65Hz and from there unbaffled dipole 18", so kind of similar to Danny, but he has servo dipoles above the F12s. 

@oldhvymec
Not familiar with what VMPSs bass is. I believe you are also into DIY OB speakers. I'm also running an active system, so no passive xo parts between amp and corresponding driver. I couldn't be happier. Currently a 4-way active stereo system...although I smell bdp24 comments might be leading me to a 5-way ;-)

Has anyone tried the Thor's Hammer?

+1 to @audiorusty on comments about JL Audio "e" series (I have an e110--superb sub for limited space) and separate crossover.

My previous sub, though wonderful sounding (SVS SB-1000) has a rather non-transparent, poor-sounding low-pass output crossover. Instead I got a very good quality Marchand electronic crossover and no longer relied on the sub's crossover. Big improvement, plus the fact is relatively few subs even have a low pass output (RCA pair), much less a good sounding one.

As it happens, my e110 is one such sub. But I found it more convenient to continue using the external crossover than the JLA's crossover output, due to a pesky ground loop.

If you don't happen to have an integrated or receiver w/quality filtered outputs for sub + mains, an external crossover is the way to go. 

@lewinskih01: Your question has me confused. After stating "So he's using F12's up to 40Hz", you then ask "Do you happen to know how high he crosses over to the F12G's?" Aren't those the same? Or am I not seeing what you're asking?

You're not differentiating between F12 and F12G, are you? The "G" designation is used in reference to GR Research, the only difference between the two models being the use of a paper cone woofer in the F12G, an aluminum in the F12. Danny prefers paper cone woofers, Rythmik's Brian Ding metal.

Danny uses the OB sub from whatever frequency is required by the loudspeaker it is used with (up to 300Hz), down to as low as it will play, which is into the teens (below 20Hz). In other words, with a low-pass filter on the sub but no high pass. When he adds a pair of F12's, he still uses the OB sub full range, without rolling off the bottom end to "make room" for the F12's.

Le me reiterate that the 40Hz figure I mentioned is the frequency I believe Danny uses the F12 up to when coupled with the OB. I may be mistaken, it could be somewhat higher, though certainly not above 80Hz.