There are a few Maggie owners using either the F12 or F15HP subs. The F12 has, as you would suspect, a 12" woofer, the F15HP a 15". They sound identical, but the 15, having a bigger cone and stronger motor (magnet), as well as bigger sealed enclosure, higher power (600w vs 370), and greater driver excursion, has more output. The difference in price is about $200, I believe. Both subs are sealed, and very clean, excellent for use with planars. The Rythmik plate amp has extensive controls, the most important being a continuously-variable phase control, an absolute requirement for a blendless seam between speaker and sub. Do NOT buy a sub without it! Rythmik also offers ported subs, which are great for extra output at and above port tuning, for large rooms such as yours (35’ length!). There is also a sealed dual 15" model with two drivers and a dual channel 400/400w amp. It’s around $1500, last I looked. In development is an 18" model, slated for release later this year.
The thing is, all Rythmiks are Servo-Feedback designs, the operating parameters of the woofers tightly controlled by the very sophisticated Rythmik feedback system. For absolute best sound with planars, the way to go is the OB/Dipole sub, as described above as well as in a new thread on Audiogon today ("Need advice on adding subs") in which I describe in greater detail the sub’s design. The OB/Dipole sub is as different from boxed subs as planar speakers are from boxed speakers. Think about it: The sub has the same figure-of-8 radiation characteristics as a planar speaker, with nulls to each side. It has no resonant sealed or ported box, same as a planar. It excites fewer room modes, just like a planar. Being an Open Baffle/Dipole sub, with the Rythmik Direct Servo-Feedback controlling of the drivers? It’s a game changer---the absolute State-Of-The-Art in subwoofers!
But the OB/Dipole requires some effort, as it is a DIY kit, and runs about $2000/pair. I’ve never heard an REL, but it must be real good, as a lot of people here like it. There are also Vandersteen sub fans, and they’re good too. I’ve heard them (at Brooks Berdan’s shop), but they are no competition for Rythmiks!
