Rythmik L12 or F12

Experience or knowledge of these compact, sealed subs...? Looking to buy a pair. Is there a significant difference between the two? About a $700 up charge for the F12s. To be paired with Salk Silk monitors...
The F12 has a high pass filter,a different woofer,a different amp! I would say that makes it a different sub!!
I can’t speak to the L12, which looks like an entry level sub, but I’ve had experience with the F series. I’m currently using an F 12 SE with a paper cone for my small HT, but originally ordered it to play with my two channel hi-fi. Well made, easy to set up and a lot of product for the money (even though you can buy cheaper subs). I recently bought a pair of the high powered F15 with the piano finish-- these do not give you the option of a paper cone driver, only aluminum. But, I’ve managed to get them to blend pretty well with my two channel audio system through placement, room treatment and settings. I’m crossing over pretty low- at 50 hz, because I’m trying to reinforce a full range speaker system that already has "woofers"- so these add a foundation. You can also add an inexpensive DSP unit, and still keep it at a reasonable budget. Talk to Brian Deng, the owner. He’s very helpful, not a "salesman" type. Good guy, good company, good product.

The Rythmik L12 and F12 have these things in common: They were both designed by Brian Ding, owner of Rythmik, a very knowledgeable and talented designer. They both have 12" drivers. And they both have the Rythmik Direct Servo-Feedback circuit built into their plate amps. But the amp itself is different in the two, as are the drivers, whether aluminum or paper coned (aluminum in the Rythmik F12, paper in the F12G, the G designating GR Research, whose Danny Richie worked on the development of the driver with Mr. Ding, as well as on the State-Of-The-Art GR Research/Rythmik Open Baffle/Dipole Direct Servo-Feedback Subwoofer, the only sub of it’s type in the world, and the best. Except for the Eminent Technology Rotary Subwoofer, of course!). And the enclosures are different. They both share the Rythmik "house sound"---stopping on a dime, as they say. No bloat and boom, lean and clean. The controls (PEQ, x/o, phase, damping) on the F12 are more extensive as well.

The choice is, as always, a matter of how much you have and are willing to spend. Jim Salk installs the F series Rythmik subs in his bigger speakers, and builds custom enclosures for both the F12 and F15.

I very recently bought 2 F12G subs. I have had the about three weeks, I could not be any happier with them. I spent about three days tweaking the set up and have not messed with them since, very musical and I just love them. Using them in a two channel system with full rang speakers. On the right material it is most satisfying,(big smiles) on everything else they do the job well. 
Rythmiks are gaining a reputation amongst planar speaker owners, particularly Maggies. Most subs are designed for home theater, but Rythmik owner/designer Brian Ding is concerned first with music reproduction. The co-designer of the paper-coned woofer in the F12G, Danny Richie of GR Research, is a hard-core audiophile---OB woofers and speakers, tube amps, perfectionist sensibilities, worked closely with tube amp maker Gary Dodd (R.I.P.). Danny & Brians OB/Dipole Subwoofer is, as preciously stated, State-Of-The-Art. But it is available as a DIY kit only, the user needing to build or have built the OB/Dipole H-frame into which the dual 12" woofers (the free-air version of the woofer in the Rythmik F12G) are installed.
You can’t go wrong with a Rythmik sub.

FWIW, I’ve been using an L12 for a few years. A single one in a relatively small environment and I’m quite happy with it. It’s a quality sound used here principally for classical music and some pop, not theater.

IIRC the output spec in db was very close to that of the F12. A major difference is that the L12 cannot be connected to the speaker; it MUST be fed from a preamp with RCA connects.

I think the owner of Rythmik, who is a real audiophile, will get on the phone with you and discuss the differences in an honest way.
On the Rythmik website, there's also something called the F12-300.
It seems this sub has a less powerful amp with fewer tuning options, but it says nothing about the driver.  The photo looks like the same driver as the F12.  I wonder if it is?

I have the f12se and have run them with Acoustat Monitor 3's and with a pair of Magnapan 1.7's that my son owns.. beefy amp.. fast and quick, might depend somewhat on what loudspeaker you are partnering with?

crossover point, etc.. but is a more expensive model so it should be a superior product.  It was right after that I saw a newer model with two 8's which you could crossover at a higher freq. I wonder how that model does?