Another professional user of Rythmik subs is Sterling Sound, the great audiophile mastering house in NYC. They have three pair of F15's in their monitoring systems.
Planar and mini-monitor speaker lovers have long had to accept the rolled-off bottom end of their speakers, and the difficulty in successfully adding subs to them. Maggies are one such speaker of course, and the bass they do have is excellent in quality. Subs good enough to blend seamlessly with them are few, and Rythmik is one such sub. The number of Maggie and mini-monitor users happy with the mating of their speakers and Rythmik's has been slowly growing, all by word-of-mouth.
Subs have traditionally been considered almost impossible to be added to the highest-quality speakers for music reproduction, but there are now a handful, many listed by the above posters. I have had a few myself, from the legendary KEF B-139 woofer (used by Dave Wilson in his WAMM model in the 70's-80's) in a folded transmission line enclosure, HSU sonotube 10", and Infinity RS-1b servo-feedback towers with six 8" woofers each. I now own pairs of both Rythmik F15HP's, and the very, very special Rythmik/GR Research OB/Dipole subs (a pair of 12" woofers mounted in Open Baffle H-frames)---producers of the highest quality bass I have yet to hear, regardless of price.
By the way, don't be "fooled" by the fact that the Rythmik L12 has an "only" 300 watt amp versus the SVS SB2000's 500 watts. Just as with any speaker, the SPL produced by a sub is determined not just by the wattage of the amp, but also by the sensitivity/efficiency of the driver(s) the amp is powering. Rythmik's woofers, due in part to their relatively low (for a woofer) mass, are more sensitive than the woofers used in most other subs. Remember, if the Rythmik L12's woofer is only 3dB more sensitive than that used in the SVS SB2000's, the Rythmik will actually have effectively more power than the SVS. I don't know that such is the case, I am just making the theoretical argument.
