I think you'll find a number of threads on the Rythmik products- I have a few of their subs but don't use them with Maggies. If @bdp24 reads this, he may help b/c he is familiar with their use in conjunction with planars. They make an open baffle type as a kit which requires you to provide the frame--something that is spec'd out for DIY or for a competent carpenter to help you assemble.
The company itself is good, as are their finished products.
I can tell you based on my experience that matching dynamic woofers with electrostats or horns is tricky, part of it depends on placement, X-over frequency, how many subs you employ and your willingness to do measurements and make adjustments. If the L12 is ported, it is not going to be comparable to the sealed box in sound. They also offer a choice of drivers, with the paper cone (GR?) version being more desirable for music. Hope that helps. Brian at Rythmik is a pretty honest guy and easy to deal w/.
Thanks for all the comments, I certainly appreciate the opinions. I have no doubt the sub brands mentioned are very good. How good is the question? Since I have budget constraints I need to go with best-bang-for the buck. Will the Boom Boom sound of the JL e110 sound three times better the the Rythmik? I guess I will have to drive my Toyota for awhile longer.
elf, if and when you want to spend more to get more, keep in mind that above a certain level, room integration will have more of an effect than the sub(s) it(them)selves. If you go to the Rythmik section in the AVS Forum, there are quite a few comments by Magneplanar speaker owners telling others about the pairing of Rythmik subs and those speakers. The F12 is a common choice with Maggies, F15 for bigger rooms. But the really interesting discussions take place on the GR Research Audio Circle Forum, in the threads relating to the unique OB/Dipole Sub created in a collaboration between Brian Ding of Rythmik and Danny Richie of GR Research. Any questions regarding the OB sub should be directed toward Danny rather than Brian.
A pair of the OB/Dipole Sub kits (each kit consists of two 12" woofers made expressly for OB use, and a plate amp with which to drive them. The amp also contains the Rythmik servo-feedback circuitry that controls the woofers, and an OB cancellation-compensating shelving circuit.) runs about $1500, and a pair of flat-pack H-frames in which to install the woofers and plate amp around $500. Assembling the H-frames is not much harder than an Ikea dresser, after you have painted or veneered (or have it done for you, as did Audiogon member kennythekey---see his Virtual System to see pics of the subs) them. THE sub for planars, as well as other high-performance loudspeakers.
Rythmik Audio dual 12" servo subwoofer. Specifications. In the chart below, with bass extension controls set to Low Music, the response is 3 db down at 18Hz. The red and blue lines are the amplitude and phase response, respectively. Mobdro
I don't have Magnepans, but I have owned many subwoofers and I don't think you can go wrong with Rythmik, SVS, or also Power Sound Audio for well made "reasonably" priced subs.
I've owned a couple of HSU subs and was less impressed with them. I currently have two Rythmik F25 subs for movies and two SVS SB13 Ultra sealed subs for my two channel system.
I also have some smaller "entry level" subs, a PSA S1500, a Rythmik F12, and SVS SB12-NSD. These are all in smaller rooms and are more than adequate for that usage.
In terms of looks, I think SVS subs look the best. In terms of sound quality, I really like Rythmik's servo technology, but SVS and PSA are no slouch in that department. The best "bang for the buck" might be PSA.
Pick the one that works best for you in terms of size, budget, and looks and you should be happy with any of those three brands.
@jetter I think the SB12-NSD is a really nice sub. I'm listening to mine right now and for the small room it's in, it's perfect. The room is maybe 12' X 15'. It does a nice job of filling in the bass for my Canton monitors. I have the gain set at about 9 o'clock and have it crossed over around 60 Hz. It gets the job done and is not being pushed at all.
What you'll gain as much as anything by going up the SVS or Rythmik (or any other manufacturer's line) is more "headroom".
My living room is pretty large and opens into my kitchen / dining area. In that space, I have two SVS SB13 Ultras for my two channel system. The SB12-NSDs would be working hard or not keeping up with my speakers in that space, while the SB13's are just coasting along. I have the volume on the subs set at something like -7. They fill in the lowest frequencies that my speakers can't adequately reproduce and provide that tactile feel of sound waves hitting you like you get at a live concert.
For home theater, I add in two Rythmik F25 subs plus a HSU MBM-12 (mid bass module). It's overkill, but none of the subs have to work very hard and it fills the room nicely when there are low frequency effects in the movie.
If you're happy with the SB12-NSDs and your room isn't too big for them and they're not straining, enjoy them. Right tool for the job and all that.