Eminent Technology LFT 7 !!

@riverdinaudio, agree about the Maggie ribbon tweeter. I have a pair of Tympani T-IVa's, which contain it. I never though of using it in place of the ribbon tweeter in the LFT-8b, as that ribbon is used only for the top octave. When I get the time, I'm gonna place the T-IVa m/t panels beside the LFT-8b panels, compare the two tweeters. Thanks for the idea!

There are a group of guys on the Planar Speaker Asylum Forum who had removed the midrange driver from the T-IVa, replacing it with multiple NEO8 drivers (seven, iirc). Haven't heard them myself, but reports are very positive.

I failed to mention it above, but the GT Audio Works sub is nothing more than the GR Research/Rythmik OB/Dipole Sub kit installed in their own H-frame, not visa versa. Credit where credit is due! The sub came from the fertile mind of GRR's Danny Richie, a long-time proponent of OB loudspeakers and subs. When he learned of Rythmik Audio Brian Ding's new servo-feedback sub system, he thought mating it with an OB woofer (which are designed specifically for that application, different from those designed for non-OB use) would create a new SOTA sub/woofer, and got to work on the design.

The sub uses the Rythmik A370 plate amp, into which Brian Ding installs a dipole cancellation-compensation network (a simple single-pole/1st-order low-pass filter). Danny designed the woofer, which is the Rythmik 12" paper cone woofer optimized for OB usage.

@gstewtoo, great to hear from another planar fanatic, especially of the Eminent Technology stripe! Bruce's speakers are ridiculously under-acknowledged and appreciated, aren't they? I'm still hoping to eventually snag a pair of LFT-6, but until then my LFT-4 and -8b will have to do. ;-)

Did you do the x/o upgrades yourself? I would like to eliminate them altogether, and use my First Watt B4 x/o in place of the speaker level filters, but Thigpen's x/o's are not textbook designs: they employ driver-compensation elements that the B4 can't replicate. Still, just bi-amping them with the B4 should produce a worthwhile improvement.

Because both the GR Research/Rythmik OB/Dipole Sub and their standard sealed enclosure subs (the F12G in the case of GRR) employ the Rythmik Servo-Feedback system, the difference between the two is not as great as it would be sans the servo. Each has it's own strengths and weaknesses in comparison to the other:

Sealed provides more output, OB less room loading as well as dipole characteristics matching that of planar loudspeakers (not just out-of-phase cancellation to either side, but also equal SPL drop off at varying distances, keeping the speaker/sub balance the same at all listening positions.). Not to mention no sealed enclosure resonance issues!

THE sub for planars is the GR Research/Rythmik OB/Dipole Sub. This has been discussed on Audiogon numerous times in the fairly recent past, so I won't bore everyone again with the reasons why. ;-)

Yes, the swarm is a great thing, but an OB/Dipole sub is more appropriate for planar loudspeakers. No reason you can't have four of them!

Oh, you own LFT-6’s. I’ve located a pair, but shipping them is a problem for the current owner, and he’s on the other side of the U.S. from me. Road trip? ;-)

At one point I owned pairs of both Tympani T-IV AND T-IVa, which is just plain silly. Now it's just the T-IVa, LFT-IV and LFT-8b, and original Quads. Oh, and a pair of ESS Transtatics. A pair of LFT-6 and I'm all set. ;-)