Regarding break-in, the MMG manual makes no mention of it. On the other hand, the manual for my Von Schweikert VR4 Gen III HSE does mention break-in. Different driver designs. Does this mean the Maggies do not go through a break-in period? I don't know, but the MMG manual is very specific on a number of topics, including placement and set-up (Have you read this section and followed the procedure? It's quite good, and it specifically addresses bass issues.). I would think if break-in was a factor with the MMG, then Magnepan would have mentioned it in the manual.