ctro---Jim Salk puts the Rythmik guts (15" servo-feedback woofer and 600w plate amp combo) into his own sealed enclosure, which has much more bracing than the Rythmik box and greater internal volume (4cu.ft. versus Rythmik's 3cu.ft.), for more efficiency and slightly more output. Jim offers the sub with beautiful wood finishes. The Ryhtmik guts are also available as a DIY kit, and you can have your own box made from the plans on the Rythmik site.
But for use with planars such as your M-L's, the sub to get is the OB/Dipole sub, co-designed by Rythmik's Brian Ding and Danny Richie of GR Research. It mates with planar speakers better than ANY other sub, regardless of price. Remember the dipole sub Gradient made for the QUAD ESL63? Picture that, but with far better woofers featuring servo feedback control. Not as much sound OUTPUT as sealed or ported subs, but superior sound QUALITY. If that's what you're looking for.
