GR-Research Line Force First Transparent Speakers?

I've been waiting to finish building these speakers for two years. I ordered enough Bohlender-Graebener NEO10 drivers from Parts Express before they became unavailable. But the company building the cabinets for me ran into Covid supply chain issues with the special composite material the cabinets are made from. I finally got the cabinets a few weeks ago and got them built up.

They only have about 25 hours on them so far, but they sound glorious. I can't wait until the crossovers are fully broken in. 

The Line Forces are being driven by DIY 300B Parallel SET monoblocks with WE new-issue tubes. The servo-controlled open-baffle woofers (three 12" drivers/channel) handle from about 170Hz and are powered by Rythmik 370W class A/B amps. 

Awesome @jaytor! I’m green with envy :-( . And I’m only a half hour or so away from you ;-) . I know of a few guys who replaced the magnetic-planar midrange driver in their Tympani T-IVa loudspeakers (which I own) with six or seven NEO-8’s. The NEO-8’s fit right in the slot the stock Magnepan driver sits in, and the owners feel the NEO-8’s provide a significant improvement to the T-IVa. But 12 or 14 NEO-8’s (when available) cost more than I paid for my T-IVa’s!

You still have your GR Research NX-Otica’s, I presume? With the OB/Dipole subs, of course. Glutton ;-) . I’ve been telling everyone about the sub for years, but you can only lead a horse to water. I suppose many are afraid of doing a simple DIY build of the H-frame the sub kit gets installed in, but anyone who did Jr. High or High School wood shop is up to the task. If I can do it, just about anyone can! I went with a W-frame (rather than an H-), and two of the 8 ohm drivers (rather than three of the 16 ohm).

@bdp24 - Thanks. I might have mentioned that I owned Tympani IVs in the mid 80's. I used Entec subwoofers (one of the first servo controlled designs), but I was never able to get these to fully integrate. I imagine that your OB subs work MUCH better. 

I'd be happy to have you over for an audition once my Line Forces are broken-in (probably a couple months for these crossover caps). 

I've always been intrigued by the Infinity IRS and Genesis One, but didn't have the budget or space for them. When I heard about the Line Forces, the idea of building a modern (and more compact) interpretation of these designs with more advanced and efficient drivers was exciting. 

It took a while to work out the details since these speakers weren't in production, but I've finally been able to complete them. Unlike the IRS and Genesis One, these are quite efficient at 98db/w, and easy to drive (impedance never drops below 5ohms), so they are a good match for low-power SET amps. 

These drivers are very clean and dynamic. The well-reviewed PS-Audio FR-30 uses similar planar drivers, but using a large number of them all but eliminates thermal compression, improves efficiency, and further reduces distortion. It also allows the drivers to play lower. 

Wow they look spectacular and I bet they sound fantastic. 

Color me green. 

For those who don’t know, the discontinuation of the original B-G NEO drivers (the NEO 3, 8, and 10) put an end to the availability of the GR Research full line-source magnetic-planar model kit (which @jaytor has just completed building), as well as the factory-built version of same by another company (whose name escapes me at the moment). Danny Richie was therefore forced to design line source open baffle models using only a single NEO 3 tweeter (which Danny has made for him) and multiple 6.5" dynamic drivers (optimized for open baffle use) for midrange and bass: the NX-Treme and the NX-Otica. Open baffle subs are used to make the models full-range ob loudspeakers. As Wendell Diller of Magnepan has for years been insisting, monopole woofers just don’t work with open baffle and planar loudspeakers (as @jaytor found with this Tympani/Entec pairing, and as did I when I had a pair of Infinity RS-1b’s)

While I have no doubt the NX-Treme and NX-Otica sound fantastic, I’m a hard core planar purist, and dynamic ("cone") drivers just don’t do it for me (though I admit I’ve never heard a line source employing them). Danny is very complimentary of the open baffle designs of Clayton Shaw of Spatial Audio, though he isn’t a fan of wide, flat baffles, choosing to go with "folded" baffles (watch the GR Research YouTube videos to learn why that is).

With the NEO drivers no longer available, I chose to stick with my planars (Tympani T-IVa, Eminent Technology LFT-4 and LFT-8b, and QUAD ESL), mated with the GR Research/Rythmik Servo-Feedback OB/Dipole Sub, a 2-woofer version of the 3-woofer sub seen in @jaytor’s pics above. One of the LFT models mated with the ob/dipole sub is in a way a modern version of the Infinity RS-1b, but without the problems of the Infinity EMIT and EMIM drivers (the ET LFT magnetic-planar drivers are far better built than were those Infinity’s, as well as the Magnepans for that matter), and with the far superior ob/dipole subs in place of the Infinity monopole woofers. If you already own a planar or open baffle loudspeaker you love, but want or need more or better bass, do yourself a huge favour and look into the ob/dipole sub.

By the way, Magnepan is hard at work preparing a new model that is to include dipole subs, and the sub will be made available separately for use with their other models. And Eminent Technology has just introduced the LFT-8c, which uses a dipole (though NOT open baffle) woofer in place of the omnipole woofer of the LFT-8b. The dipole woofer is available to current 8b owners, who can simply remove the LFT panel from the "b" woofer enclosure and bolt it on the new "c" dipole, for full range dipole music reproduction. A new crossover is included, which includes DSP and EQ, and a power amp for the woofer. $1500/pr. Imagine how much Wilson and/or Magico would charge for them ;-) .