Two points:
- The Rythmik sub plate amp allows for high-level hook-up to binding posts (on the main speaker’s power amp), like Rel’s.
- OB/Dipole subs (such as the GR Research/Rythmik), their figure-of-8 radiation pattern creating a null to each side of the sub, do not excite the sidewall-to-sidewall resonance mode that Monopoles do, therefore creating less of the "room boom" often associated with and attributed to subs.
There is, unfortunately, a price to be paid for those otherwise-advantageous nulls: a corresponding bass cancellation that increases with descending frequency---a 6dB/octave, 1st order acoustic roll-off. Rythmik designer Brian Ding compensates for that roll-off by installing a complimentary 6dB/octave bass boosting "shelf" into the plate amp which comes with the OB/Dipole Sub kit, which counter-acts the roll-off, resulting in bass response claimed to be flat into the teens. Clever fellow.
When using a Magneplanar Tympani as bass augmentation, the panel can be butted right up against a side wall, with a significant resultant benefit: A prevention of the normal dipole cancellation, as the front and back opposite-polarity waves can’t meet and cancel each other, the path obstructed by the wall. That results in the absence of the 1st order, 6dB/octave roll-off inherent in a dipole speaker. Hence, no dipole bass roll-off (at least not from that end of the panel). Free extra output to a lower frequency, with no extra cost, or penalty!
