rythmikaudio subwoofers

They look very interesting, but you understand, I assume that these are DIY in terms of the cabinets.

yes , i saw that but i can always have my friend build it (cabinet) . i am more interested in the sound & how it would compare to the jl Fathom or velodyne DD series.

I'm thinking the same thing. Good winter project for me and one of my buddies who is just starting to move up to entry high end stuff. As you can tell, they do not have the digital room correction of the DD (or Velodyne SMS-1). Bobby recommends running the VSMs full range and crossing over to a sub at about 30 hz; the crossover in the rythmiks bottoms out at 40 hz. That should be OK if you bypass the BAM, but you would then have to high pass the input to the VSM or you would get excessive cone excursion and significant distortion (I know, it happened once to me accidentally and it is unlistenable).