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No experience, but I believe (could be wrong) that McIntosh uses the Lyngdorf correction scheme, which is different than all of the other DRC units (including DEQX) out there. As I understand it, Lyngdorf/Mc compares nearfield and farfield measurements to remove room effects (i.e. it essentially removes the difference in the farfield response and delivers the nearfield result). The goal is to remove the room effects heard at the listening position but otherwise leave the speaker's native response unchanged. If the speaker has a hump in the anechoic response, you'll hear it with this system.
All of the other schemes take measurements at the listening position(s, plural for Audyssey) and Eq that curve to a target (which, generally speaking, means flat). If the speaker has a hump in the anechoic response, it will be flattened.
All of this per a coversation with the Lyngdorf tech guys 3 or 4 years ago, so it's to the best I can recall.