I'm willing to bet that the "slap" occurs around 200hz which is at the crossover point of the DWM.
There isn't much you can do about it and a sub is not going to help it at that frequency.
There's no reason Magnepan shouldn't be able to address this issue, but they are somewhat eccentric and unconventional about a lot of things. Just look at their weird speaker connection with an atypical allen wrench size.
It's just a trade-off for buying what otherwise is a great speaker value and technology.
There isn't much you can do about it and a sub is not going to help it at that frequency.
There's no reason Magnepan shouldn't be able to address this issue, but they are somewhat eccentric and unconventional about a lot of things. Just look at their weird speaker connection with an atypical allen wrench size.
It's just a trade-off for buying what otherwise is a great speaker value and technology.