They [Ayre] go on to say that their 3rd generation filters "combine Craven's minimum-phase digital filter with a slower roll-off that reduced the overall amount of ringing. The resulting filter has no pre-echoes, and only about 1 cycle of post-ringing."
Meridian isn't using the filter published in Craven's paper. At the AES talk, Bob showed a diagram of the filter which clearly had a slow roll-off. It also had a deliberately-crafted null at twice the Nyquist frequency (IIRC). In other words, I believe that Meridian is using a state-of-the-art filter. I can't recall whether or not Bob showed the impulse response though.
Edit: Clearly though, apodizing/minimum-phase filters are "in vogue" and we have Meridian to thank for pursuing (and funding) this direction of research. Knowing Meridian's penchant for secrecy, I have no doubt that they have not revealed their "special sauce" which is applied on top of the basic, published, research.
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