I like the concept, the Planar PL-2 is -6 dB at 24 Hz, in room. That's low, not many audiophiles have heard tight, true 24 Hz at home; and I'm not talking about the flubby home theater 24 Hz a big ported sub produces. REL is known for quick bass that can blend with true planar speakers so I would assume these subs will be quick too.
Planer is a shorter, better name than "FlatPiston LongThrow Dipole Speaker" which, when turned into an anagram is: "Planar Tones — Soft Highs, Wide Pole, Toolkit." Neither name rolls off the tongue as easily as the shorted Planar. I think REL used an anagram finder.